DOCSLIB.ORG

Characterization of a Defective Pbwo4 Crystal Cut Along the Ac

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Characterization of a Defective Pbwo4 Crystal Cut Along the Ac Prepared for submission to JINST Characterization of a defective PbWO4 crystal cut along the a-c crystallographic plane: structural assessment and a novel photoelastic stress analysis L. Montalto,a P.P. Natali,b F. Davíb P. Menguccic N. Paonea D. Rinaldic;1 aDIISM, bDICEA, cSIMAU, Universitá Politecnica delle Marche, via Brecce Bianche 12, 60131 Ancona, Italy E-mail: [email protected] Abstract: Among scintillators, the PWO is one of the most widely used, for instance in CMS calorimeter at CERN and PANDA project. Crystallographic structure and chemical composition as well as residual stress condition, are indicators of homogeneity and good quality of the crystal. In this paper, structural characterization of a defective PbWO4 (PWO) crystal has been performed by X-ray Diffraction (XRD), Energy Dispersive Spec- troscopy (EDS) and Photoelasticity in the unusual (a; c) crystallographic plane. XRD and EDS analysis have been used to investigate crystallographic orientation and chemical composition, while stress distribution, which indicates macroscopic inhomogeneities and defects, has been obtained by photoelastic approaches, in Conoscopic and Sphenoscopic configuration. Since the sample is cut along the (a; c) crystallographic plane, a new method is proposed for the interpretation of the fringe pattern. The structural analysis has detected odds from the nominal lattice dimension, which can be attributed to the strong presence of Pb and W. A strong inhomogeneity over the crystal sample has been revealed by the photoelastic inspection. The results give reliability to the proposed procedure which is exploitable in crystals with other structures. Keywords: Scintillators and scintillating fibers and light guides, Calorimeters, Detection of defects arXiv:1711.03403v2 [physics.ins-det] 12 Dec 2017 1Corresponding author. Contents 1 Introduction1 2 Experiments2 2.1 Sample description2 2.2 Structural characterization3 2.3 Novel Photoelastic measurements in the (a − c) plane4 2.4 Data interpretation: the proposed elasto-optic model5 2.5 Photoelastic tests and results7 2.5.1 Conoscopic inspection7 2.5.2 Sphenoscopic inspection8 3 Discussion9 4 Conclusions 11 1 Introduction Application areas of scintillating crystals span from high energy physics to security, to ge- ological prospections and medical applications [1,2]. PWO, as a scintillating material, is continuing getting attention from the high energy physics community [3,4], since the time of CMS [5] and, also, today with the PANDA [4]-[6] project, thanks to its intrinsic charac- teristics. Owing to its own scintillating properties, the tetragonal PbWO4 (PWO) crystals are among the widely used and studied [2], [4], [7]-[9]. The fields themselves prompt the efforts in theoretical, experimental and technological studies of these substances and the associated production processes. In addition to purely theoretical aspects, from the tech- nological point of view, a high-quality mass production requires to deepen the knowledge of crystal structure as well as of mechanical and optical behavior of crystals, in order to address growth process technologies. From the industrial point of view, the development of procedures and reliable methods of inspection and characterization is mandatory for a more and more efficient production, improving the process control, the crystal quality and reduc- ing the costs. In order to achieve these goals, the development of experimental techniques and theoretical models, capable of improving knowledge of crystal behavior as well as their characteristics and structure, is necessary [8], [10, 11]. In most cases, quality control proce- dures involve identification and quantification of defects present in the crystal sample. For this purpose, methods aimed at the study and the inspection of matter like X-ray diffraction (XRD), scanning electron microscopy (SEM) and microanalysis (EDS) allow for a quanti- tative characterization of crystalline structure, composition and lattice orientation. Fast, non-destructive and reliable quality control techniques of birefringent material are based on – 1 – optical crystallography [12] and photoelasticity [13, 14]. These techniques are aimed at the study and investigation of the interference isochromate and isogyre fringes, generated by birefringent effects. The fringe patterns depend by the crystal structure [15, 16], stress state (applied and/or residual) and defectiveness of the sample. Photoelastic studies, carried out by the implementation of reliable polariscopes [17, 18], are fundamental in the comprehen- sion of defect dynamics and crystal reliability. For PWO and similar materials, photoelastic analysis is quite well established in case of samples observed in the plane normal to the optic axis [18]-[21]. On the contrary, although samples cut parallel to the optic axis have been already observed [12], [22], fringe patterns in this configuration have not been completely analysed yet (to our best knowledge), despite their importance for both crystal theoretical knowledge and assessment of production processes reliability and efficiency. In this paper, we report results of structural characterization of a quasi-cylindrical PWO, performed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and microanalysis (EDS) as well as photoelastic investigations, carried out by Conoscopy and Sphenoscopy [23]. The sample is cut with the c axis parallel to the observation plane, therefore a model, which links easy measurable quantities of the fringe pattern to the sample stress condition, is proposed. The model for the data interpretation, which is an innovative contribution of the work, is based on studies already reported in literature [14, 15], [24]-[26] and allows for information on both stress and the piezo-optic tensor Π components [27]-[29]. The obtained results put in evidence a great inhomogeneity of the sample, which are well in accord with the clear defectiveness of the PWO sample and underline the reliability of the photoelastic methods and the related model. 2 Experiments 2.1 Sample description The quasi-cylindrical single crystal of lead tungsten oxide has a nominal composition PbWO4 (stolzite) and it has been grown by the Czochralski method. The PbWO4 (PWO) has a body-centered tetragonal crystallographic structure with lattice parameters a = 0:54619 nm and c = 1:2049 nm (ICDD card n.19-708). PWO is a high-density mate- 3 rial with ρ = 8:26 g/cm . This crystal is uniaxial negative (no > ne), with extraordinary and ordinary refraction indices ne = 2:163 and no = 2:234, for the visible radiation with λ = 632:8 nm [11]. The ingot grown with its axis normal to the crystallographic c−axis has been cut into slices, so that the investigated surface should be parallel to the c−axis of the crystal. In Figure1, the pictures of the PWO slice under inspection are reported; the sample presents some defects clearly visible by the front and the side picture. Visible scratches and chipping on the top right of the Figure1a are defects occurred during the machining while, the sliding effect, which induced the quasi-cylindrical geometry, is due to the grown procedures. Both the issues can be referable to the rising and the consolidation of a residual stress distribution during the growth. This has led to a non- homogeneous state. – 2 – Figure 1. Pictures of the defective sample. In the Figure (a), the black line traced on the surface indicates the direction of the c crystallographic axis; scretches and chipping occured during the machining are clearly visible on the surface. By the Figure (b), the distorted cylindrical shape is evident. Both the issue can be due to the rise of residual stress and defects during the growth. 2.2 Structural characterization The investigation of the structure of this PWO sample has been carried out by X-ray Diffrac- tion (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). X-ray diffraction (XRD) measurements have been performed by a Bruker D8 Advance diffractometer operating at V= 40 kV and I= 40 mA, with Cu-K(α) radiation. A θ ÷ 2θ geometry has been used to investigate growth orientation of the crystal while a rocking curve (RC) in the angular range θ = 14◦ ÷ 22◦ has been carried out to put into evidence possible preferential orientations. Furthermore, in order to measure the lattice parameters of the crystal, an XRD powder pattern in the angular range 2θ = 20◦ ÷ 80◦ has been obtained from a splinter of the sample reduced to powder by manually grinding into a mortar. Peak analysis has been performed using the Origin software [www.origiblab.com]. The quantitative results of peak analysis are reported as provided by Origin. Scanning electron microscopy (SEM) observations have been carried out by a Zeiss Supra 40 field emission microscope equipped with a Bruker Z200 energy dispersive (EDS) microanalysis. The resulting patterns of the XRD analyses performed on the as-produced (AP) sample and on sample reduced to powder are reported in Figure2. Furthermore, the rocking curve obtained from the AP sample to check the degree of the preferential growth is shown in the inset of Figure2. The XRD pattern of the AP sample (Figure2) clearly evidences a (2; 0; 0) preferential growth. This means that the (2; 0; 0) lattice planes of the PWO crystal grow parallel to the sample surface. The rocking curve reported in the inset of Figure2 confirms the preferential orientation growth. Quantitative analysis of the (2; 0; 0) reflection in Figure2 (AP sample) allows estimating the exact peak position at 2θ = 32:686 ± 0:001◦ with a full width at half maximum (FWHM) of 0:507 ± 0:003◦. Compared to the nominal value ◦ (2θ = 32:754 ) of the (2; 0; 0)) reflection for the PbWO4 (Stolzite) compound reported in the ICDD (International Centre for Diffraction Data) card n.19-708, the experimental value – 3 – Figure 2. XRD patterns of PWO crystal in as produced (AP) condition and after grinding to powder. Inset shows the rocking curve obtained from the AP sample. obtained in our case results to be only 0:2% lower. The rocking curve in the inset in Figure2 shows a peak located at θ = 18:278 ± 0:001◦ with a FWHM of 0:236 ± 0:003◦.
Load more

Recommended publications
  • Newsletter June 2006
    w NEWSLETTER INTERNATIONAL TUNGSTEN INDUSTRY ASSOCIATION Rue Père Eudore Devroye 245, 1150 Brussels, Belgium Tel: +32 2 770 8878 Fax: + 32 2 770 8898 E-mail: [email protected] Web: www.itia.info The programme will begin on Tuesday Toxicologic Assessment for the Production and 19th evening with a Reception in the hotel jointly Mechanical Processing of Materials containing hosted by Tiberon Minerals and ITIA. Tungsten Heavy Metal. Not least will be an introduction to the formation of a Consortium to deal Working sessions will be held on Wednesday Annual with the implications of REACH on behalf of the and Thursday mornings and papers will tungsten industry, both legal and financial. include: General Readers will recall that REACH will place an obligation ▼ HSE work programme on individual companies to submit a technical dossier and register any chemical substance Meeting ▼ Ganzhou’s Tungsten Industry and Its Progress manufactured or imported into the EU in quantities ▼ Geostatistics in the mid and long-term planning for of more than 1 tonne. the Panasqueira deposit (Nuno Alves, Beralt Tin Tuesday 26 to and Wolfram) In order to assist companies with the registration process, the Commission recommends the creation ▼ Thursday 28 Paper by Zhuzhou Cemented Carbide of industry Consortia. These Consortia will enable the ▼ Update on Tiberon’s Development of Tungsten joint development, submission and sharing of September 2006 Mining in Vietnam information with the aim of reducing the compliance burden on individual companies and preventing ▼ Update on China’s Tungsten Industry Hyatt Regency Hotel, unnecessary additional animal testing. ▼ Update on US Tungsten Market (Dean Schiller, Boston, USA OsramSylvania Products) Both members and non-members will be equally ▼ Review of Trends in 2006 (Nigel Tunna, Metal-Pages) welcome to join the Consortium, saving themselves considerable amounts of money and time by so doing.
    [Show full text]
  • Mineral Collecting Sites in North Carolina by W
    .'.' .., Mineral Collecting Sites in North Carolina By W. F. Wilson and B. J. McKenzie RUTILE GUMMITE IN GARNET RUBY CORUNDUM GOLD TORBERNITE GARNET IN MICA ANATASE RUTILE AJTUNITE AND TORBERNITE THULITE AND PYRITE MONAZITE EMERALD CUPRITE SMOKY QUARTZ ZIRCON TORBERNITE ~/ UBRAR'l USE ONLV ,~O NOT REMOVE. fROM LIBRARY N. C. GEOLOGICAL SUHVEY Information Circular 24 Mineral Collecting Sites in North Carolina By W. F. Wilson and B. J. McKenzie Raleigh 1978 Second Printing 1980. Additional copies of this publication may be obtained from: North CarOlina Department of Natural Resources and Community Development Geological Survey Section P. O. Box 27687 ~ Raleigh. N. C. 27611 1823 --~- GEOLOGICAL SURVEY SECTION The Geological Survey Section shall, by law"...make such exami­ nation, survey, and mapping of the geology, mineralogy, and topo­ graphy of the state, including their industrial and economic utilization as it may consider necessary." In carrying out its duties under this law, the section promotes the wise conservation and use of mineral resources by industry, commerce, agriculture, and other governmental agencies for the general welfare of the citizens of North Carolina. The Section conducts a number of basic and applied research projects in environmental resource planning, mineral resource explora­ tion, mineral statistics, and systematic geologic mapping. Services constitute a major portion ofthe Sections's activities and include identi­ fying rock and mineral samples submitted by the citizens of the state and providing consulting services and specially prepared reports to other agencies that require geological information. The Geological Survey Section publishes results of research in a series of Bulletins, Economic Papers, Information Circulars, Educa­ tional Series, Geologic Maps, and Special Publications.
    [Show full text]
  • Crystal Structure of Lead Tungstate at 1.4 and 300 K
    Crystal structure of lead tungstate at 1.4 and 300 K R. Chipaux1, G. André2, A. Cousson2 1CEA/DSM/DAPNIA/SED, CE-Saclay, 91191 Gif sur Yvette cedex, France 2CEA/DSM/DRECAM/LLB, CE-Saclay, 91191 Gif sur Yvette cedex, France Abstract The crystal structure of lead tungstate, PbWO4, is tetragonal, scheelite type, space group I41/a. This compound is frequently subjected to lead deficiency, due to the difference in the vapour pressure of the two oxides, WO3 and PbO, used in the crystal growth. One group has reported that lead vacancies can order in a crystal structure derived from the scheelite type, but of lower symmetry and described by the space group P4/nnc or P4 . We report here on neutron diffraction measurements performed on three different powdered samples. Our measurements do not show any indication of structural transition between 1.4 and 300 K. The structure is undoubtedly the tetragonal one. The existence of a lead deficient structure remains unconfirmed. Keywords : Lead tungstate, crystal structure, neutron diffraction 1. Introduction Lead tungstate, PbWO4, is a scintillator now widely used in particle and nuclear physics [1] and intense research and development works are under way. It occurs in nature as tetragonal stolzite, of scheelite type, space group I41/a [2] and monoclinic raspite, space group P21/a [3]. A high pressure form, with space group P21/n has also been reported [4]. The common form for the industrial crystals used in particle detection is the scheelite type. Following X-ray diffraction studies on lead deficient crystals, a distortion of this structure described by the space group P4/nnc has been suggested by Moreau et al.
    [Show full text]
  • Optical Absorption and Applications of the ABO4 (A=Ca, Pb and B= Mo, W) Semiconductors
    Optical absorption and applications of the ABO4 (A=Ca, Pb and B= Mo, W) semiconductors C. Tablero Instituto de Energía Solar, E.T.S.I. de Telecomunicación, Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, SPAIN. e-mail: [email protected] Tlf: +34 915495700 Fax: +34 915446341 Abstract Ternary molybdates and tungstates ABO4 (A=Ca, Pb and B= Mo, W) are a group of materials that could be used for a variety of optoelectronic applications. We present a study of the optoelectronic properties based on first-principles using several orbital- dependent one-electron potentials applied to several orbital subspaces. The optical properties are split into chemical-species contributions in order to quantify the microscopic contributions. Furthermore, the effect of using several one-electron potentials and orbital subspaces is analyzed. From the results, the larger contribution to the optical absorption comes from the B-O transitions. The possible use as multi-gap solar cell absorbents is analyzed. Keywords: scheelite, electronic structure, optical properties, semiconductors. 1. Introduction For optoelectronic applications is need to develop new types of materials responding to visible light irradiation. This response is a consequence of the electronic and optical properties. ABO4 (A = Ca, Pb and B = Mo or W) molybdates and tungstates are two families of materials with interesting luminescence and structural properties. 1 They have promising applications for solid state lasers [1], scintillators [2-4], electro- optical devices [5], etc. Calcium and lead molybdates and tungstates are natural minerals. Furthermore, they can be made synthetically. The mineral names associated with these materials are powellite (CaMoO4), scheelite (CaWO4), wulfenite (PbMoO4), and stolzite (PbWO4).
    [Show full text]
  • Langhofite, Pb2(OH)[WO4(OH)], a New Mineral from Långban, Sweden
    Mineralogical Magazine (2020), 84, 381–389 doi:10.1180/mgm.2020.28 Article Langhofite, Pb2(OH)[WO4(OH)], a new mineral from Långban, Sweden Dan Holtstam1 , Fernando Cámara2 and Andreas Karlsson1 1Department of Geosciences, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden; and 2Università degli Studi di Milano, Dipartimento di Scienze della Terra ‘A. Desio’, Via Luigi Mangiagalli 34, 20133, Milano, Italy Abstract Langhofite, ideally Pb2(OH)[WO4(OH)], is a new mineral from the Långban mine, Värmland, Sweden. The mineral and its name were approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2019- 005). It occurs in a small vug in hematite–pyroxene skarn associated with calcite, baryte, fluorapatite, mimetite and minor sulfide miner- als. Langhofite is triclinic, space group P1, and unit-cell parameters a = 6.6154(1) Å, b = 7.0766(1) Å, c = 7.3296(1) Å, α = 118.175(2)°, β = 94.451(1)°, γ = 101.146(1)° and V = 291.06(1) Å3 for Z = 2. The seven strongest Bragg peaks from powder X-ray diffractometry are [dobs,Å(I )(hkl)]: 6.04(24)(010), 3.26(22)(112), 3.181(19)(200), 3.079(24)(112), 3.016(100)(020), 2.054(20)(311) and 2.050(18)(132). Langhofite occurs as euhedral crystals up to 4 mm, elongated along the a axis, with lengthwise striation. Mohs hardness is ca. 2½, – based on VHN25 data obtained in the range 130 192. The mineral is brittle, with perfect {010} and {100} cleavages. The calculated dens- – ity based on the ideal formula is 7.95(1) g⋅cm 3.
    [Show full text]
  • Tungsten Minerals and Deposits
    DEPARTMENT OF THE INTERIOR FRANKLIN K. LANE, Secretary UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, Director Bulletin 652 4"^ TUNGSTEN MINERALS AND DEPOSITS BY FRANK L. HESS WASHINGTON GOVERNMENT PRINTING OFFICE 1917 ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 25 CENTS PER COPY CONTENTS. Page. Introduction.............................................................. , 7 Inquiries concerning tungsten......................................... 7 Survey publications on tungsten........................................ 7 Scope of this report.................................................... 9 Technical terms...................................................... 9 Tungsten................................................................. H Characteristics and properties........................................... n Uses................................................................. 15 Forms in which tungsten is found...................................... 18 Tungsten minerals........................................................ 19 Chemical and physical features......................................... 19 The wolframites...................................................... 21 Composition...................................................... 21 Ferberite......................................................... 22 Physical features.............................................. 22 Minerals of similar appearance.................................
    [Show full text]
  • Complex Utilization of Treatment Wastes from Thermal Power Plants
    A.N.Shabarov, N.V.Nikolaeva DOI 10.18454/PMI.2016.4.607 Complex utilization of treatment wastes from thermal power plants UDC 662.73 COMPLEX UTILIZATION OF TREATMENT WASTES FROM THERMAL POWER PLANTS A.N.SHABAROV, N.V.NIKOLAEVA Saint-Petersburg Mining University, Russia The paper investigates present-day challenges related to accumulation, processing and disposal of the coal combustion wastes. The analysis of technogenic materials beneficiation practices using gravitation, magnetic and flo- tation beneficiation methods has been carried out. Quantitative and qualitative microscopic analysis of materials has been conducted. The study target were ash and slag wastes (ASW) from thermal power plant and coal combustion ash. Most metals are contained in coals and coal ashes in fine-dispersed (1-10 μm) mineral form. Various native met- als and intermetallic compounds, sulfides, carbonates, sulfates, tungstates, silicates, rare earths phosphates and nio- bates have been discovered. Each metal may occur in several mineral phases, for instance tungsten may be in the form of wolframite, stolzite, ferberite, scheelite and represented by impurities. Not only composition of compounds is diversified, but also morphology of grains: well-defined and skeleton crystals, aggregates and polycrystalline struc- tures, crystal twins and fragments; druses, globules and microspherules; porous shapes, flocculous and splintery clus- ters, lumpy aggregations, etc. Based on chemical silicate analysis of main ASW components the petrochemical prop- erties of material have been assessed. Preliminary analyses have shown that concentration of ferrum-bearing compo- nents in ASW is around 5-11 %. The magnetic method of technogenic waste beneficiation with the help of high- gradient magnetic separation has been studied.
    [Show full text]
  • A Specific Gravity Index for Minerats
    A SPECIFICGRAVITY INDEX FOR MINERATS c. A. MURSKyI ern R. M. THOMPSON, Un'fuersityof Bri.ti,sh Col,umb,in,Voncouver, Canad,a This work was undertaken in order to provide a practical, and as far as possible,a complete list of specific gravities of minerals. An accurate speciflc cravity determination can usually be made quickly and this information when combined with other physical properties commonly leads to rapid mineral identification. Early complete but now outdated specific gravity lists are those of Miers given in his mineralogy textbook (1902),and Spencer(M,i,n. Mag.,2!, pp. 382-865,I}ZZ). A more recent list by Hurlbut (Dana's Manuatr of M,i,neral,ogy,LgE2) is incomplete and others are limited to rock forming minerals,Trdger (Tabel,l,enntr-optischen Best'i,mmungd,er geste,i,nsb.ildend,en M,ineral,e, 1952) and Morey (Encycto- ped,iaof Cherni,cal,Technol,ogy, Vol. 12, 19b4). In his mineral identification tables, smith (rd,entifi,cati,onand. qual,itatioe cherai,cal,anal,ys'i,s of mineral,s,second edition, New york, 19bB) groups minerals on the basis of specificgravity but in each of the twelve groups the minerals are listed in order of decreasinghardness. The present work should not be regarded as an index of all known minerals as the specificgravities of many minerals are unknown or known only approximately and are omitted from the current list. The list, in order of increasing specific gravity, includes all minerals without regard to other physical properties or to chemical composition. The designation I or II after the name indicates that the mineral falls in the classesof minerals describedin Dana Systemof M'ineralogyEdition 7, volume I (Native elements, sulphides, oxides, etc.) or II (Halides, carbonates, etc.) (L944 and 1951).
    [Show full text]
  • Minerals of Arizona Report
    MINERALS OF ARIZONA by Frederic W. Galbraith and Daniel J. Brennan THE ARIZONA BUREAU OF MINES Price One Dollar Free to Residents of Arizona Bulletin 181 1970 THE UNIVERSITY OF ARIZONA TUCSON TABLE OF CONT'ENTS EIements .___ 1 FOREWORD Sulfides ._______________________ 9 As a service about mineral matters in Arizona, the Arizona Bureau Sulfosalts ._. .___ __ 22 of Mines, University of Arizona, is pleased to reprint the long-standing booklet on MINERALS OF ARIZONA. This basic journal was issued originally in 1941, under the authorship of Dr. Frederic W. Galbraith, as Simple Oxides .. 26 a bulletin of the Arizona Bureau of Mines. It has moved through several editions and, in some later printings, it was authored jointly by Dr. Gal­ Oxides Containing Uranium, Thorium, Zirconium .. .... 34 braith and Dr. Daniel J. Brennan. It now is being released in its Fourth Edition as Bulletin 181, Arizona Bureau of Mines. Hydroxides .. .. 35 The comprehensive coverage of mineral information contained in the bulletin should serve to give notable and continuing benefits to laymen as well as to professional scientists of Arizona. Multiple Oxides 37 J. D. Forrester, Director Arizona Bureau of Mines Multiple Oxides Containing Columbium, February 2, 1970 Tantaum, Titanium .. .. .. 40 Halides .. .. __ ____ _________ __ __ 41 Carbonates, Nitrates, Borates .. .... .. 45 Sulfates, Chromates, Tellurites .. .. .. __ .._.. __ 57 Phosphates, Arsenates, Vanadates, Antimonates .._ 68 First Edition (Bulletin 149) July 1, 1941 Vanadium Oxysalts ...... .......... 76 Second Edition, Revised (Bulletin 153) April, 1947 Third Edition, Revised 1959; Second Printing 1966 Fourth Edition (Bulletin 181) February, 1970 Tungstates, Molybdates.. _. .. .. .. 79 Silicates ...
    [Show full text]
  • Sandwich” Wulfenite from the Ojuela Mine, Mapimí, Mapimí Municipality Durango, Mexico: Evidence of Preferred Secondary Nucleation on Selected Wulfenite Faces
    Philippine Journal of Science 150 (2): 527-533, April 2021 ISSN 0031 - 7683 Date Received: 08 Sep 2020 Characterization of “Sandwich” Wulfenite from the Ojuela Mine, Mapimí, Mapimí Municipality Durango, Mexico: Evidence of Preferred Secondary Nucleation on Selected Wulfenite Faces J. Theo Kloprogge1,2* and Jessebel P. Valera-Gadot3 1Department of Chemistry, College of Arts and Sciences University of the Philippines Visayas, Miag-ao, Iloilo 5023 Philippines 2School of Earth and Environmental Sciences, The University of Queensland Brisbane 4072 Queensland, Australia 3Material Science and Nanotechnology Laboratory Regional Research Center – Office of the Chancellor University of the Philippines Visayas, Miag-ao, Iloilo 5023 Philippines This paper describes the formation of “sandwich” wulfenite. Banded wulfenite from the Ojuela Mine, Mapimí, Durango, Mexico, have been found since 2017, but an explanation for the band formation has not been provided. X-ray diffraction (XRD) showed the wulfenite to have a tetragonal unit cell of a = 5.4374(1), c = 12.1123(7) Å. The Raman spectrum was dominated by –1 –1 ν1 (Ag) around 870 cm , while the weak shoulder at 859 cm represents the strain activated ν1 –1 –1 (Bu) infrared (IR) band. Two ν2 modes were observed at 318 cm (Ag) and 351 cm (Bg). For the –1 –1 ν3(Eg), the band at 768 cm was assigned to the Bg symmetric mode and the 745 cm band to the –1 Eg vibration. The IR spectrum showed two strong bands at 835 and 779 cm corresponding to –1 v3 modes and a very weak one at 496 cm . SEM-EDX (scanning electron microscopy – energy dispersive X-ray analysis) showed that the band does not extend into the main crystal but is limited to the surface as secondary growth.
    [Show full text]
  • Discovery of Stolzite in China and Refinement of Its Crystal Structure
    Vol.8No.1 ACTA GEOLOGICA SINICA March 1995 • 111 • Discovery of Stolzite in China and Refinement of Its Crystal Structure Xu Keqin, Xue Jiyue, Ding Yang, Department ofEarth Sciences, Nanjng University, Nanjng, Jiangsu and L ti G uanglie Central Laboratory ofH angzhou University, H angzhou, Z hejang Abstract Although stolzite was discovered in Yaogangxian, Hunan Province, China, in 1948, no for­ mal report about this mineral has been published. Recently its crystal structure has been refined by means of the Rietveld method. The cell dimensions of the mineral are: a =b = 0.544S03(3) nm, c= 1.20495(1) nm and a= P=y=90° . The X, Y and Z coordinates of the atom 0 refined by the authors are 0.2637, 0.1137 and 0.0706, respectively. The length of the W -0 bond is 0.17826 nm and the angle of the 0 - W -0 bound are 1230 and 1030 ,respectively. Key words' stolzite, Rietveld method, refinement of crystal structure, Yaogangxian, Hunan Province 1 Course of Discovery Stolzite is a secondary mineral occurring in the oxidizing zone of the tungsten deposit. No formal report of the mineral has been pUblished yet in China. When Xu Keqin and Ji Shouyuan made an investigation in a wolframite mine at Yaogangxian, Zixing, Hunan, in the summer of 1947, they discovered the first skarn-type scheelite deposit of China at Heshangtan on the southeast side of this mine (Xu, 1957). In the summer of the next year, Xu Keqin together with Jin Wanlin again went to Heshangtan, Yaogangxian, to carry out geological and topographic surveys in the scheelite district and stayed in Lin~ s residence.
    [Show full text]
  • Standard X-Ray Diffraction Powder Patterns
    E^l Admin. NBS MONOGRAPH 25—SECTION 5 Refecii^M not to be ^ferlrom the library. Standard X-ray Diffraction Powder Patterns ^\ / U.S. DEPARTMENT OF COMMERCE S NATIONAL BUREAU OF STANDARDS THE NATIONAL BUREAU OF STANDARDS The National Bureau of Standards^ provides measurement and technical information services essential to the efficiency and effectiveness of the work of the Nation's scientists and engineers. The Bureau serves also as a focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To accomplish this mission, the Bureau is organized into three institutes covering broad program areas of research and services: THE INSTITUTE FOR BASIC STANDARDS . provides the central basis within the United States for a complete and consistent system of physical measurements, coordinates that system with the measurement systems of other nations, and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. This Institute comprises a series of divisions, each serving a classical subject matter area: —Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic Physics—Physical Chemistry—Radiation Physics— -Laboratory Astrophysics^—Radio Standards Laboratory,^ which includes Radio Standards Physics and Radio Standards Engineering—Office of Standard Refer- ence Data. THE INSTITUTE FOR MATERIALS RESEARCH . conducts materials research and provides associated materials services including mainly reference materials and data on the properties of ma- terials. Beyond its direct interest to the Nation's scientists and engineers, this Institute yields services which are essential to the advancement of technology in industry and commerce.
    [Show full text]