Process for Preparing Metal Halides by the Sol-Gel Method

Europaisches Patentamt (19) European Patent Office Office europeenpeen des brevets EP 0 71 3 840 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention (51) mt ci.6: C01 F 1 1/20, C01 F 1 1/22, of the grant of the patent: C01F 11/34, C01F 17/00, 29.09.1999 Bulletin 1999/39 C01B9/00, C01B9/04, C03C (21) Application number: 95420313.9 C01B9/08, 17/22, C01F5/28 (22) Date of filing: 15.11.1995

(54) Process for preparing metal halides by the sol-gel method Verfahren zur Herstellung von Metallhalogeniden mittels Sol-Gel-Verfahren Procede de preparation des halogenures metalliques par voie sol-gel

(84) Designated Contracting States: (74) Representative: Fevrier, Murielle Frangoise E. BE CH DE ES FR GB IT LI NL KODAK INDUSTRIE Departement Brevets - CRT (30) Priority: 23.11.1994 FR 9414309 Zone Industrielle - B.P. 21 71102 Chalon-sur-Saone Cedex (FR) (43) Date of publication of application: 29.05.1996 Bulletin 1996/22 (56) References cited: EP-A- 0 125 721 US-A- 5 051 278 (73) Proprietors: • KODAK-PATHE • NOUVEAU JOURNAL DE CHIMIE, vol. 5, no. 10, F-75594 Paris Cedex 12 (FR) 1981 GAUTHIER-VILLARS, pages 479-484, J. L. Designated Contracting States: NAMY ET AL. 'Smooth synthesis and FR characterization of divalent samarium and • EASTMAN KODAK COMPANY ytterbium derivatives' Rochester, New York 14650-2201 (US) • JOURNAL OF MATERIALS SCIENCE LETTERS, Designated Contracting States: vol. 11, no. 3, February 1992 LONDON GB, pages BE CH DE ES GB IT LI NL 152-154, XP 000248754 C. RUSSEL 'Preparation of LiF, CaF2 and YF3 by thermal decomposition (72) Inventor: Poncelet, Olivier Jean Christian, of the metal trifluoroacetates' Kodak-Pathe F-71102 Chalon sur Saone Cedex (FR)

DO o ^- 00 CO Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice the Patent Office of the Notice of shall be filed in o to European opposition to European patent granted. opposition a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. a. 99(1) European Patent Convention). LU

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Description tained by the decomposition of a metal fluoride precursor. [0001] The present invention concerns a process for [0012] For example, in US patent 4 492 721 , magne- obtaining metal halides, in particular rare earth and/or sium fluoride layers are obtained by the decomposition alkaline earth halides, and novel materials in powder, 5 of fluorinated organic compounds of magnesium, such film or bulk material form obtained from these metal hal- as magnesium trifluoroacetate. ides. [0013] US patents 5 051 278 and 5 271 956 describe [0002] Metal halides are compounds which have a process for forming films of metal fluorides, in partic- been known for a long time. For example, alkaline earth ular binary and ternary alkaline earth or lanthanide flu- fluorides (group I IA), 4th period transition metal fluorides 10 orides. or rare earth fluorides (group NIB) are known. These This process consists of forming a coating solution con- metal fluorides have interesting electrical, magnetic and taining a non-fluorinated organometallic compound, a optical properties. solvent and afluorination agent and coating this solution [0003] Alkaline earth fluorides have low refractive in- on a support. The film thus obtained is then heated at a dexes, which enables them to be used in an anti-reflec- is temperature of approximately 500°C in order to decom- tive layer on supports with a high reflective index. pose the products contained in the coating solution into [0004] The layers obtained from these fluorides in pure metal fluoride. In order to obtain a uniform layer, a general have low dielectric constants, are transparent temperature increase is effected with a gradient of and have excellent mechanical properties. around 50°C/min. [0005] All these special properties mean that metal 20 [0014] US patents 5 208 101 and 5 268 196 describe fluorides are compounds which are advantageous for a process for forming layers comprising alkali metal or piezoelectric, ferromagnetic or anti-ferromagnetic, elec- alkaline earth fluorides using sol-gel technology. This tro-optical, pyroelectrical or non-linear optics applica- process consists of forming a layer on a glass substrate tions. using a coating solution containing a light metal oxide [0006] Mixed rare earth and alkaline earth metal hal- 25 precursor, a non-aqueous solvent and water, heating ides are also known as luminescent substances used the layer in order to density the layer of light metal ox- for example to convert X-rays or gamma radiation into ides, and exposing this densified layer at a high temper- visible light. ature to a gaseous current containing fluorine. The den- [0007] Many publications describe the use of mixed sification of the oxide layer is effected at a temperature alkaline earth halides as luminescent substances, in 30 of around 500°C and the fluorination is effected at tem- particular in radiographic products. peratures of around 300°C. [0008] For example, European patent EP 149148 de- [0015] In all the known processes set out above, the scribes radiographic image recording screens which metal halide layers are obtained using high tempera- contain, in the storage layer, a mixed alkaline earth hal- tures, either to vaporise the metal halides or to decom- ide of general formula BaF(XY):Eu:Sr in which X and Y 35 pose a precursor of the metal halides, or to density the are halide atoms. These luminescent substances are base metal oxide layer and to halogenate this same lay- obtained by mixing BaF2, BaCI2, BaBr2, EuF3 and SrCI er. in a ball mill. The mixture is then baked red hot in a bro- [0016] All these processes enabling layers of metal mium vapour chamber for 1 to 5 hours at a temperature halides to be obtained have many drawbacks related to of between 800 and 1000°C. After cooling, the product 40 the necessity to use high temperatures. In particular, the is broken up, washed and then dried. In this way the choice of the support for the metal halide layer is very luminescent substance described above is obtained. limited. In addition, at high temperature, it is very difficult This technique, which is difficult to implement, does not to obtain homogeneous metal halide layers having con- make it possible to control the stoichiometry of the final trolled stoichiometry. product. 45 [001 7] The object of the present invention concerns a [0009] It is known that thin layers of luminescent sub- process for obtaining homogeneous metal halides at stances can be formed by chemical vapour phase dep- low temperature, in powder, layer, fibre or bulk material osition. Such layers are obtained with difficulty because form. of the differences in vapour tension and stability of each [0018] The present invention makes it possible to of the constituents. so eliminate the problems relating to the use of high tem- [0010] A process for obtaining layers of metal fluo- peratures. For example, the process of the present in- rides was described in US patent 3 475 192. Such a vention makes it possible to obtain metal halide layers process consists of coating, on a substrate, a magnesi- on amuch widervariety of supports, in particular organic um fluoride solution in a polar solvent and heating the supports which have very little resistance to high tem- substrate thus covered at between 100 and 1000°C. In 55 peratures. this process, it is necessary, in order to obtain a film, to [0019] The process for preparing alkaline earth and/ use a substrate which is resistant to high temperatures. or rare earth metal halides of the present invention con- [0011] It is known that metal fluoride layers can be ob- sists of forming a homogeneous solution by mixing one

2 3 EP 0 713 840 B1 4 or more rare earth and/or alkaline earth halogenoalkox- yield of such a synthesis depends in particular on the ides in an anhydrous organic solvent and adding to this steric hindrance of the alcohol used. The smaller the solution a quantity of water which is at least stoichiomet- steric hindrance, the faster will be the synthesis of the ric in order to hydrolyse the halogenoalkoxides. alkaline earth alkoxides. The alcohol is preferably cho- [0020] Within the scope of the invention, the halog- 5 sen from amongst methanol, ethanol or propanol. enoalkoxides and consequently the metal halides may [0032] The rare earth alkoxides can be synthesised contain one or more halogen atoms chosen from according to one of the following two methods. amongst fluorine, bromine, chlorine and iodine. [0033] The first method consists of reacting a rare [0021] Figure 1 is an FT-Raman spectrum of the bar- earth chloride, for example lanthane chloride, directly ium fluoroalkoxide used to obtain, according to the in- 10 with an alkali metal alkoxide, for example a sodium or vention, barium fluoride. lithium alkoxide. This synthesis has drawbacks related [0022] Figure 2 is an X-ray diffraction spectrum of a to the presence of chloride in the reaction medium. In barium fluoride powder obtained by hydrolysis of the addition, lanthanide chlorides are particularly stable barium fluoroalkoxide of Figure 1 . chemical species which are difficult to activate, which [0023] Figure 3 is an X-ray diffraction spectrum of a is gives rise to low reaction yields. europium fluoride powder obtained according to the [0034] A second method of synthesising rare earth process of the present invention. alkoxides consists of reacting the rare earth directly with [0024] Figure 4 is a spectrum obtained by energy dis- an alcohol such as 2-propanol or a functionalised alco- persive X-ray microanalysis, of the compound hol such as 2-methoxyethanol. YYbBaTm0 1 Fx obtained by hydrolysis, at room temper- 20 [0035] Within the scope of the invention, it is also pos- ature, of a mixture of rare earth and alkaline earth fluor- sible to use heterometal oxides obtained by mixing sev- oalkoxides as in Example 7. eral homometal oxides. [0025] Figure 5 is the emission spectrum of the com- [0036] According to the present invention, the rare pound YYbBaTm0 1FX in powder form excited by laser earth or alkaline earth halogenoalkoxides of the inven- at 650 nm. ts25 tion are obtained by alcoholisation of rare earth or alka- [0026] The metal halides which can be obtained by line earth alkoxides by a halogenated or perhalogenated the process of the present invention are for example hal- alcohol hereinafter referred to as a "halogenoalcohol". ides of elements in group IIAsuch as beryllium, magne- [0037] For example, when it is desired to prepare met- sium, calcium, strontium, barium or radium halides or al fluorides according to the process of the present in- halides of elements in group NIB, such as scandium, yt- 30 vention, it is possible to prepare the corresponding rare trium, lanthane and cerium, gadolinium, erbium or ytter- earth and/or alkaline earth fluoroalkoxide by reacting bium halides. For example, the metal halides which can one or more rare earth and/or alkaline earth alkoxides be obtained are barium bromide, barium fluoride, bari- with a fluoroalcohol chosen from amongst um bromofluoride, magnesium fluoride, magnesium 1 ,1 ,1 ,3,3,3-hexafluro-2-propanol, perfluoro-tert-buta- bromide, ytterbium fluoride, barium and thulium fluoride, 35 nol, 2,2,2-trifluoroethanol, 2-fluoroethanol, cerium bromide, cerium (III) fluoride, europium fluoride, 1,1,1,2,2,3,3-heptafluoro-4-butanol or 2,2,3,4,4,4-hex- etc. afluoro-l-butanol. [0027] According to the invention, mixed metal hali- [0038] When it is desired to prepare metal bromides des, for example rare earth and alkaline earth halides, according to the process of the present invention, it is can also be obtained. 40 possible to prepare the rare earth and/or alkaline earth [0028] The alkaline earth and/or rare earth halides of bromoalkoxide by reacting one or more rare earth and/ the invention are obtained from one or more rare earth or alkaline earth alkoxides with a bromoalcohol chosen and/or alkaline earth halogenoalkoxides, which can be from amongst 2-bromoethanol, 3-bromo-2-propanol, obtained by any one of the known methods of the art. 3-bromo-2-methyl-1 -propanol or 3-bromo-2,2-dimethyl- These halogenoalkoxides are put in solution in an an- 45 1 -propanol. hydrous solvent, which may be chosen from a large [0039] These halogenoalkoxides can be defined by number of organic solvents. The preferred solvents of the formula M(ORx)n(ORy)m in which M is a rare earth the invention are anhydrous organic solvents which are or an alkaline earth, Rx and Ry are each separately alkyl miscible in water, such as, for example, tetrahydro- groups containing one or more identical or different hal- furane, alcohols or ketones. 50 ogen atoms, and n and m are such that the sum of n [0029] The rare earth and/or alkaline earth halog- and m is equal to the valency of M. enoalkoxides are in general obtained from the corre- [0040] When it is desired to obtain a metal halide con- sponding alkaline earth or rare earth alkoxide or alkox- taining several halides, a halogenoalkoxide as defined ides. above in which the groups Rx and Ry are differently hal- [0030] The preparation of the alkaline earth alkoxides 55 ogenated is preferably used. It is also possible to use may be effected by various syntheses known in the art. as a starting halogenoalkoxide a halogenoalkoxide of [0031] The easiest synthesis to implement consists of formula M(ORx)nXm in which M, Rx, n and m as defined reacting an alcohol directly on an alkaline earth. The previously and X is a halogen atom.

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[0041] The alkaline earth halogenoalkoxides can also made from organic polymer materials. The preferred or- be prepared by directly reacting the alkaline earth in so- ganic supports are supports with reactive groups at the lution in a polar solvent with a halogenoalcohol as de- surface, for example hydroxyl groups as in cellulosic fined previously. When fluoroalkoxides are prepared, supports. the reaction is highly exothermic, which causes a deg- 5 [0049] The deposition of a metal halide layer of the radation of the organic compounds present in the reac- invention on a cellulose support makes it possible for tion medium. In this case, the reaction can be catalysed example to improve the resistance to pH of such a sup- and must be carried out under very severe anhydrous port. conditions. When bromoalkoxides are prepared, the re- [0050] According to one embodiment, layers of metal action is not exothermic and must be catalysed by form- 10 fluorides on a cellulose support were thus obtained. ing in situ a highly reactive species such as an amidide [0051] The process of the invention also makes it pos- by the addition of NH3, Et2NH or (Me3Si)2NH in the re- sible to obtain a material having a controlled stoichiom- action medium. etry since it is very easy to control the metal halog- [0042] According to one embodiment of the invention, enoalkoxide concentration of the starting solution. In ad- in order to prepare a mixed metal halide containing sev- 15 dition, since the layers of metal halides of the invention eral metal elements, each of the metal halogenoalkox- are obtained using perfectly homogeneous solutions, ides forming part of the final composition of the metal homogeneous metal halide layers are obtained, which halide are prepared separately. is not the case with the prior art. [0043] According to the invention, the hydrolysis may [0052] According to the prior art, it is known that, by be catalysed by means of an acid. Preferably, this acid 20 hydrolysis of metal alkoxides, metal oxides are formed. is halogenated with the same halogen as the one con- Such a process is generally implemented at low temper- stituting the final metal halide in order to avoid the pres- ature in order to form inorganic lattices of metal oxides, ence of secondary products related to the counterion as- for example polysiloxane lattices. sociated with the hydrogen. For example, hydrolysis of [0053] It is therefore particularly surprising that, by hy- the fluoroalkoxides was effected at a pH of less than 7, 25 drolysis of halogenoalkoxides, alkaline earth or rare and preferably between 1 and 3, in the presence of hy- earth halides rather than alkaline earth or rare earth ox- drofluoric acid. ides are obtained. [0044] The quantity of water used to hydrolyse the [0054] Without being bound by theoretical considera- halogenoalkoxides according to the invention varies in tions, it appears that the hydrolysis conditions are par- accordance with the type of material desired. When it is 30 ticularly important for obtaining rare earth and/or alka- desired to obtain the metal halides of the invention in line earth halides. This is because it appears that rapid the form of layers or fibres, hydrolysis of the halog- hydrolysis favours the formation of halides rather than enoalkoxides is effected with a quantity of water which the formation of oxides. Halogenoalkoxides, in particu- is at least stoichiometric and less than 5 times, and pref- lar fluoroalkoxides, have a hydrophobic character, erably less than twice, this stoichiometric quantity. 35 which brings about the formation of micelles in the re- [0045] When it is desired to obtain powders, this action medium. Each micelle fulfils the role of a micro- quantity of water may be up to 50 times and preferably reactor in which the hydrolysis is accelerated, which fa- 10 to 30 times greater than the stoichiometric quantity vours the formation of metal halides rather than the for- of water for hydrolysing the halogenoalkoxides. mation of metal oxides. [0046] The present invention surprisingly makes it 40 possible to obtain pure rare earth or alkaline earth hali- EXAMPLES des at low temperature. The process and the metal halides of the invention are particularly useful for manufac- [0055] All the following reactions were carried out in turing organic/inorganic devices in thin film, fibre or solid an inert gas, at room temperature. material form. 45 [0056] The materials obtained were analysed by the [0047] Within the scope of the invention, thin layers following techniques: of metal halides were obtained dip-coating a support in a solution of metal halogenoalkoxides and hydrolysing FT-RAMAN spectroscopy, which consists of irradi- the halogenoalkoxides of this layer solely by means of ating a sample with a monochromatic laser and atmospheric moisture. The thickness of the layer can be so measuring the frequency of the dispersed light. varied either by varying the initial concentration of metal halogenoalkoxides or by dip-coating several times the X-ray diffraction, which consists of irradiating the support covered with a first layer obtained according to surface of a sample by means of a beam of parallel the process of the present invention. monochromatic X-rays and studying the variation in [0048] The supports which can be used to obtain lay- 55 intensity as a function of the angle of incidence. X- ers within the scope of the present invention can be con- ray diffraction affords qualitative identification of the ventional supports such as glass or ceramics or sup- crystalline material and notably determination of the ports degradable at high temperature, such as supports crystalline structure.

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Energy dispersive X-ray microanalysis spectrosco- EXAMPLE 4 - Synthesis of Tm[OCH(CF,)ol, py (ED-XRMA), which enables the elements present in a sample to be identified. This identifica- [0062] A mixture of 2-methoxyethanol and 2-propanol tion is based on the exploitation of the X-rays emit- (7.5/7.5 ml) is added to a solution of 1 g (5.9 mmol, Aldri- ted by a sample bombarded by an electron beam 5 chR) of thulium in 20 ml of toluene. The reaction medium focused on the surface, each chemical element is then refluxed whilst stirring for 2 days. After filtration having a characteristic line. of the reaction medium, a colourless filtrate is obtained which is concentrated and then purified by crystallisa- [0057] From the teaching of the examples described tion. In this way 1.67 g of Tm(OCH2CH2OCH3)3 is ob- below, rare earth and/or alkaline earth halides contain- 10 tained (yield 72%). ing one or more halide atoms can easily be obtained. [0063] 2.1 g of 2-hexafluoropropanol is added to a solution of 1.67 g of Tm(OCH2CH2OCH3)3 in anhydrous EXAMPLE 1 - Synthesis of BafOCHfCFg),!? tetrahydrofurane. The reaction is exothermic. In this way, after crystallisation in a mixture of anhydrous pen- [0058] 38 g of 2-hexafluoropropanol is added to a mix- 15 tane and ethyl ether, 2.06 g of Tm[OCH(CF3)2]3 is ob- ture consisting of 15 g of barium (0.109 moles, AldrichR) tained (yield 98%). and 1 00 ml of anhydrous tetrahydrofurane. The mixture is left to react for 12 hours whilst being stirred (a highly EXAMPLE 5 - Synthesis of BaF? exothermic reaction). The reaction medium is filtered and a colourless filtrate is recovered, which is then dried 20 [0064] 5 g of barium (36 mmol) is put in solution in 50 and crystallised in anhydrous hexane. In this way 48 g ml of anhydrous tetrahydrofurane, and then 12.2 g of of Ba[OCH(CF3)2] characterised by the Raman spec- 2-hexafluoropropanol is added to form the barium fluor- trum of Figure 1 is obtained (yield 95%). oalkoxide of Example 1 . The reaction is exothermic. The reaction medium, which has become clear, is hydro- EXAMPLE 2 - Synthesis of Y[OCH(CF,)olo ps25 lysed at room temperature by the addition of 6.48 g of water. The hydrolysis is exothermic. In this way 6.3 g of [0059] 100 ml of freshly distilled 2-propanol is added BaF2 powder is obtained. to a mixture consisting of 16.1 gof yttrium (0.181 moles; [0065] Figure 2 is an X-ray spectrum of the BaF2 pow- AldrichR) and 100 ml of anhydrous toluene. 13 mg of der thus obtained. HgCI2 is then added to the reaction medium. The reac- 30 [0066] The same experiment was carried out by hy- tion medium is then refluxed whilst stirring for 2 days. drolysing the reaction medium with a solution of HF and After filtration of the medium, the filtrate is concentrated a solution of HCI04. In this case, the hydrolysis is more and then purified by crystallisation in a dichloromethane/ rapid and BaF2 is obtained as before. toluene mixture (50/50). In this way 32 g of YsO(OiPr)13 is obtained (yield 72%). 35 EXAMPLE 6 - Synthesis of MgF9 [0060] 15 g of YsO(OiPr)13 (0.0122 moles) in solution in 50 ml of anhydrous tetrahydrofurane and 27 g of [0067] 1 00 ml of absolute methanol is added to 5 g of 2-hexafluoropropanol are mixed (exothermic reaction). magnesium in chip form. The reaction is exothermic. A In this way Y[OCH(CF3)2]3 is obtained, which is then pu- white suspension is thus obtained. 70 g of 2-hexafluor- rified in anhydrous hexane (34 g, yield 95%). 40 opropanol is then added to this suspension drop by drop in order to form the corresponding magnesium fluoro- EXAMPLE 3 - Synthesis of Yb[OCH(CFq)dq alkoxide. The reaction is exothermic and the reaction medium clears. After eliminating the colloidal residues [0061] A mixture of 2-methoxyethanol and 2-propanol by filtration, the clear filtrate is hydrolysed at room tem- (30/70 ml) is added to a mixture consisting of 18.3 g of 45 perature by the rapid addition of 38 g of H20. 7.9 g of ytterbium (0.105 moles, AldrichR) and 100 ml of anhy- MgF2 is then obtained. drous toluene. The reaction medium is refluxed whilst stirring for 2 days. After filtration of the reaction medium EXAMPLE 7 - Synthesis of EuFq and crystallisation of the raw product, 33 g (80%) of Yb (OCH2CH2OCH3)3 is obtained. so [0068] In accordance with the method of the previous 25 g of 2-hexafluoropropanol is added to a solution of examples, fluorinated alcohol HOCH(CF3)2 was reacted 20 g (0.05 moles) of Yb(OCH2CH2OCH3)3 in tetrahydro- with a europium alkoxide Eu(OCH2CH2OCH3)3. In this furane (exothermic reaction). After filtration of the reac- way europium fluoroalkoxide Eu[OCH2(CF3)2] was tion medium and crystallisation of the raw product in an- formed, which by hydrolysis made it to obtain perfectly hydrous hexane, 32 g of Yb[OCH(CF3)2]3 is obtained 55 crystallised europium fluoride, at room temperature. (yield 96%). The quantity of water used is equal to 30 times the stoichiometric hydrolysis quantity. [0069] Figure 3 is an X-ray diffraction spectrum of the

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EuF3 powder obtained. EXAMPLE 10 - Synthesis of BaBr?

EXAMPLE 8 - Synthesis of a mixed rare earth and [0080] 5.7 g of barium (41 mmol) is mixed, under ar- alkaline earth fluoride gon, with 50 ml of anhydrous tetrahydrofurane, and then 5 4 ml of 2-bromoethanol is added drop by drop in order [0070] 4.03 g of Ba[OCH(CF3)2]2 is added to 5 g of to form barium bromoalkoxide. The reaction is not exo- Yb[OCH(CF3)2]3 in solution in 50 ml of anhydrous tet- thermic and it is catalysed by the controlled introduction rahydrofurane. A second solution containing 5.71 g of of two equivalents of hexamethyldisilazane. The reac- Yb[OCH(CF3)2]3 in anhydrous tetrafurane and 0.11 g of tion is accelerated by introducing 30 ml of methanol into Tm[OCH(CF3)2]3 is then added to this solution. 10 the reaction medium. The reaction medium, which is [0071] The mixture thus obtained is stirred strongly for stirred, becomes clear. 1 hour and then transferred to a Teflon reactor and hy- [0081] When the barium is completely used up, the drolysed with 40 ml of water containing 0.5 ml of 40% solution is concentrated and a white solid is obtained, HF. barium bromoalkoxide Ba(OCH2CH2Br). [0072] Avery rapid increase in the viscosity of the mix- 15 [0082] Ba(OCH2CH2Br) was also obtained by direct ture is observed, which is maintained under strong stir- alcoholisation of Ba(OEt)2. ring for one night. The reaction medium is then filtered [0083] The white solid thus obtained is solubilised in and in this way, after drying, a white powder is obtained, ethanol. Hydrolysis of the medium is then effected by the structure of which was confirmed by ED-XRMA (Fig- the addition of a quantity of water 10 to 30 times the ure 4). 20 stoichiometric hydrolysis quantity. The reaction is exo- [0073] This powder, when it is excited by a laser with thermic. After stirring for 30 min, a white crystallised a wavelength of 650 nm, emits blue light, as shown by powder is obtained. This powder was analysed by FT- Figure 5. RAMAN spectrometry. The spectrum obtained has two very fine large bands at 41 6 and 442 cm-1 , Comparison EXAMPLE 9 - Synthesis of a thin layer of BaF9 fluoride 25 of this spectrum with the spectrum obtained with BaBr2, H20 manufactured by Aldrich shows that barium bro- [0074] A cellulose substrate (NadirR sold by Roth) is mide has indeed been obtained. immersed in a solution of Ba[OCH(CF3)2] (0.1 M) in ab- [0084] The X-ray diffractometry spectrum of the pow- solute ethanol, the system being maintained under an der obtained shows unambiguously the presence of a inert gas. The substrate is then withdrawn and left in the 30 crystalline phase identical to that of the commercial open air for 5 min. Hydrolysis takes place with atmos- product. pheric moisture. [0085] Consequently the present process makes it [0075] After 5 min, the substrate is immersed into os- possible to manufacture extremely pure hydrated bari- mosed water in order to terminate the hydrolysis. um bromide from the metal at room temperature. [0076] A layer of BaF2 is thus obtained. Such layers 35 are stable even when they are immersed in solutions EXAMPLE 11 - Synthesis of SrBr9 having pH values varying between 8 and 1 2, for several days. [0086] 3.8 g of strontium (4.2 1 0"2 mol) is dissolved in [0077] In order to measure the hydrophobia of the lay- 80 ml of methanol under argon atmosphere. The reac- ers of BaF2 of the invention, the wetting angle of the pre- 40 tion is exothermic with the release of hydrogen. When viously obtained layer and that of the cellulose substrate the strontium is completely used up, a crystallised white before deposition of the layer were measured: powder corresponding to Sr(OCH3)2 is recovered. [0087] 8 g of Sr(OCH3)2 (12.3 mmol) is dissolved un- Wetting angle der argon atmosphere in 60 ml of anhydrous tetrahydro- 45 furane, and then 2 ml of 2-bromoethanol is added drop Nadir® cellulose 36 + 2 degrees by drop. layer 74 + 4 degrees BaF2 [0088] In this way a white solid is obtained which is dissolved in 30 ml of methanol. Hydrolysis of the medi- [0078] The results show that the process of the um is then effected by the addition of 15 ml of water. present invention makes it possible to obtain hydropho- so50 Fine colloidal particles in suspension are thus formed. bic layers resistant to any variation in pH. After 30 min of stirring, the solution is concentrated: a [0079] Tests showed that layers of variable thickness white crystallised power is obtained. could be obtained by modifying the concentration of [0089] This powder, analysed by FT-RAMAN spec- starting alkoxides and reimmersing the BaF2 layer in the trometry and X-ray diffractometry, has a structure iden- starting alkoxide solution. 55 tical to that of the commercial product SrBr2 manufactured by StremR.

6 11 EP 0 713 840 B1 12

EXAMPLE 12: Synthesis of BaBrF halogenoalkoxides in an anhydrous organic solvent, and [0090] 3.5 g of Ba[OCH(CF3)2]2 (7.5 mmol synthe- (2) adding to this solution a quantity of water sised in accordance with the method of Example 1) in which is at least stoichiometric for hydrolysing solution in 40 ml of anhydrous methanol is added to 2.9 s the halogenoalkoxides. g of Ba(OCH2CH2Br)2 (7.5 mmol synthesised in accordance with the method of Example 10) in solution in 40 2. Process according to Claim 1, in which the halog- ml of anhydrous methanol. The reaction medium is enoalkoxide comprises one or more atoms of halo- stirred for 3 hours at room temperature and then con- gens chosen from amongst fluorine, bromine, chlo- centrated. In this way a white powder Ba(OCH2CH2Br) 10 rine and iodine. (OCH(CF3)2 is isolated, characterised by FT-RAMAN. [0091] This barium bromofluoroalkoxide in solution in 3. Process according to Claim 1 , in which the hydrol- 20 ml of methanol is hydrolysed by the addition of a 0.2 ysis is catalysed by means of an acid. M solution of hydrofluoric acid. The solution becomes cloudy and, after concentration, a slightly coloured solid 15 4. Process according to Claim 3, in which the pH of is obtained. the hydrolysis is between 1 and 3. [0092] This powder is analysed by FT-RAMAN, ED- XRMA and X-ray diffractometry. 5. Process according to Claim 1 , in which the solvent is chosen from amongst tetrahydrofurane, alcohols The FT-RAMAN spectrum has two bands at 212.3 20 or ketones. and 238.9 cm-1 , which correspond to the Ba-F bond. 6. Method according to any of Claims 1 to 5, for pro- X-ray spectrometry microanalysis confirms the ducing homogeneous layers of rare earth and/or al- presence of the three elements Ba, Br and F. kaline earth halides, which consist of applying a so- 25 lution of rare earth and/or alkaline earth halog- The diffraction spectrum is entirely comparable to enoalkoxides in an anhydrous organic solvent to a the reference spectrum of BaBrF crystals. support and placing this layer in contact with a quantity of water which is at least stoichiometric for EXAMPLE 13: Another method of synthesising BaBrF hydrolysing the halogenoalkoxides of the layer and 30 less than 5 times and preferably less than twice this [0093] 25.6 g of Me4NOH,5H20 is heated at 1 00°C in stoichiometric quantity. order to remove the water by azeotropic distillation. The anhydrous Me4NOH solid is then dissolved in 60 ml of 7. Process according to Claim 6, in which the hydrol- anhydrous ethanol, and then 30 g of anhydrous BaBr2 ysis is effected with atmospheric moisture. is added thereto. After stirring for half a day, a precipitate 35 of NMe4Br is recovered. This compound is then dis- 8. Process according to Claim 6 for producing layers solved in 9.4 ml of hexafluoropropanol. After stirring, the of rare earth and/or alkaline earth fluorides. solution is filtered and the solvent is removed under vac- uum. 40 g of (CF3)CHOBaBr is thus recovered in the 9. Process according to Claim 6 for producing layers form of a white solid. 40 of rare earth and/or alkaline earth bromide. [0094] (CF3)CHOBaBr is solubilised in methanol and this solution is hydrolysed by the addition of water. The 10. Process according to Claim 6 for producing layers solid obtained is placed in an oven at 250°C in order to of rare earth and/or alkaline earth bromofluoride. eliminate any organic species still present. [0095] The heat treatment is not obligatory. The same 45 11. Film of rare earth and/or alkaline earth halides ob- product was obtained after drying at a much lower tem- tainable by the process according to any of Claims perature but for a longer time. 6 to 10, in which the support is an organic support [0096] X-ray diffraction analysis confirms that BaBrF degradable at high temperature. has indeed been obtained. 50 12. Film according to Claim 11 , in which the support is a support having hydroxyl groups at the surface. Claims 13. Film according to Claim 12, in which the support is 1. Process for preparing rare earth and/or alkaline a cellulosic organic polymer. earth metal halides which consists of 55

(1) forming a homogeneous solution by mixing one or more rare earth and/or alkaline earth

7 13 EP 0 713 840 B1 14

Patentanspriiche nem der Anspruche 6 bis 1 0, in welchem der Trager ein organischer Trager ist, der bei hoher Tempera- 1. Verfahren zur Herstellung von Seltenerd- und/oder tur abbaubar ist. Erdalkalimetallhalogeniden, welches darin besteht, dal3 man 5 12. Film nach Anspruch 1 1 , in welchem der Trager ein Trager ist, der Hydroxylgruppen an der Oberflache (1) eine homogene Losung durch Mischen ei- aufweist. nes oder mehrerer Seltenerdund/oder Erdalka- lihalogenalkoholaten in einem wasserfreien or- 13. Film nach Anspruch 12, in welchem der Trager ein ganischen Losungsmittel bildet und 10 organisches cellulosisches Polymer ist. (2) zu dieser Losung eine Menge Wasser gibt, die mindestens stochiometrisch fur die Hydro- lyse der Halogenalkoholate ist. Revendications

2. Verfahren nach Anspruch 1, in welchem das Halo- is 1. Procede de preparation d'halogenures metalliques genalkoholat ein oder mehrere Atome von Haloge- de terres rares et/ou d'alcalino-terreux qui consiste nen umfaBt, die aus Fluor, Brom, Chlor und lod aus- a gewahlt sind. (1) former une solution homogene en melan- 3. Verfahren nach Anspruch 1 , in welchem die Hydro- 20 geant un ou plusieurs halogenoalcoxydes de lyse mittels einer Saure katalysiert wird. terres rares et/ou d'alcalino-terreux dans un solvant organique anhydre, et 4. Verfahren nach Anspruch 3, in welchem der pH der (2) ajouter a cette solution une quantite d'eau Hydrolyse zwischen 1 und 3 liegt. au moins stoechiometrique pour hydrolyser les 25 halogenoalcoxydes. 5. Verfahren nach Anspruch 1, in welchem das Lo- sungsmittel aus Tetrahydrofuran, Alkoholen oder 2. Procede selon la revendication 1 dans lequel Ketonen ausgewahlt ist. I'halogenoalcoxyde comprend un ou plusieurs ato- mes d'halogenes choisis parmi le fluor, le brome, le 6. Verfahren nach irgendeinem der Anspruche 1 bis 5 30 chlore et I'iode. zur Herstellung von homogenen Schichten aus Sel- tenerd- und/oder Erdalkalihalogeniden, welches 3. Procede selon la revendication 1 dans lequel I'hy- darin besteht, dal3 man eine Losung von Seltenerd- drolyse est catalysee par un acide . und/oder Erdalkalihalogenalkoholaten in einem wasserfreien organischen Losungsmittel auf einen 35 4. Procede selon la revendication 3 dans lequel le pH Trager aufbringt und diese Schicht mit einer Menge de I'hydrolyse est compris entre 1 et 3. von Wasser in Kontakt bringt, die zumindest stochiometrisch fur die Hydrolyse der Halogenalko- 5. Procede selon la revendication 1 dans lequel le sol- holate der Schicht ist und weniger als das 5-fache vant est choisi parmi le tetrahydrofuranne, les alco- und vorzugsweise weniger als das 2-fache dieser 40 ols ou les cetones. stochiometrischen Menge ist. 6. Procede pour obtenir des couches homogenes 7. Verfahren nach Anspruch 6, in welchem die Hydro- d'halogenures de terres rares et/ou d'alcalino-ter- lyse mit atmospharischer Feuchtigkeit bewirkt wird. reux qui consiste a appliquer une solution d'haloge- 45 noalcoxydes de terres rares et/ou d'alcalino-terreux 8. Verfahren nach Anspruch 6 zur Herstellung von dans un solvant organique anhydre sur un support Schichten aus Seltenerdund/oder Erdalkalifluori- et a mettre en contact cette couche avec une quan- den. tite d'eau au moins stoechiometrique pour hydrolyser les halogenoalcoxydes de la couche et inferieu- 9. Verfahren nach Anspruch 6 zur Herstellung von 50 re a 5 fois, de preference inferieure a 2 fois cette Schichten aus Seltenerdund/oder Erdalkalibromid. quantite stoechiometrique.

10. Verfahren nach Anspruch 6 zur Herstellung von 7. Procede selon la revendication 6 dans lequel I'hy- Schichten aus Seltenerdund/oder Erdalkali- drolyse s'effectue avec I'humidite de I'air. bromofluorid. 55 8. Procede selon la revendication 6 pour realiser des 11. Film aus Seltenerd- und/oder Erdalkalihalogeni- couches de fluorures de terres rares et/ou d'alcali- den, erhaltlich durch das Verfahren nach irgendei- no-terreux.

8 15 EP 0 713 840 B1 16

9. Procede selon la revendication 6 pour realiser des couches de bromure de terres rares et/ou d'alcalino-terreux.

10. Procede selon la revendication 6 pour realiser des s couches de bromofluorure de terres rares et/ou d'alcalino-terreux.

11. Film d'halogenures de terres rares et/ou d'alcalino- terreux susceptible d'etre obtenu par le procede se- 10 Ion I'une quelconque des revendications 6 a 10 dans lequel le support est un support organique susceptible de se degrader a haute temperature.

12. Film selon la revendication 11 dans lequel le sup- 15 port est un support ayant des groupes hydroxyles en surface.

13. Film selon la revendication 12 dans lequel le support est un polymere organique cellulosique. 20

Jo Ml 'in

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Jo ~cn

1 00' 0

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I i EP 0 713 840 B1

EMISSION SPECTRUM OF YYbBaTm0>1Fx POWDER EXCITED BY MEANS OF A LASER AT 650 nm

500 450

NANOMETRES

FIG.5