Tanねlum Penねchlorid』E with Ammo血血the Vapor Pkase An《量properties of the Tan．Tal㎜ N’Itride Forme通

676 DENKI KAGAKU

Fomation Process of Tanね1㎜Nitri－e by the Reaction of Tanねlum Penねchlorid』e with Ammo血血the VaPor Pkase an《量Properties of the Tan．tal㎜ N’itride Forme通

Akimasa YAJIMA＊，Ryoko MATsuzAKI＊and Yuzo SAEKI＊

The reaction products of gaseous TaC15with ammonia were TaCl5・5NH3at2QO。CラTaC15・5 NH3，Ta3N5，NH4Cl at250～600℃，Ta3N5and NH4Cl at650～950。C，Ta3N5，Ta4N5・and NH4Cl at 10000C，and Ta4N5シTa2N，θ一TaN，ε一TaN，NH4Cl，and HCl at1100～1400。C．In the vapor、phase reaction of gaseous TaCl5with ammonia，the reaction of gaseous TaC15with ammonia to form TaCI5・5NH3㏄curs丘rst．Above6α．235。C，the TaC15・5NH3reacts with ammonia to form Ta3N5． Above侃．1000。C，the Ta3N5decomposes to Ta4N5．Above侃。1100。C，in addition to these reactiolls， the nitriding of tantalum，formed by the reduction of gaseous TaCI5with hydrogen resulting from the thermal dissociation of ammonia，also o㏄urs to form Ta2Nシθ一TaN，andε一TaN．On heating the Ta3N5，formed by the vapor－phase reaction，in an argon atmosphere，it changed to Ta4N5at6α・ 9000C，to Ta5N6，θ一TaN，andε一TaN at6α．1100。C，and then toθ一TaN andε一TaN at1300～1400。C． The tantalum nitrides formed above1200。C were uniform，ultra丘ne powders with the particle diametersoftheorderof1／100粋m．

11ntroduction 2 Experimental The vapor－phase reaction of transition metal 2．1Materials chlorides with ammonia has recently become The TaCl，used was prepared by the reaction important for the preparation of6ne powders of tantalum powder（Ta99．8形，Hermann C． or thin丘lms of transition metal nitrides，which Starck Berlin）with chlorine at350℃and puri一 are aquiring importance as new industrial ma－丘ed by fractional sublimatlon．The chemical terials． analysis gave Ta50．5％1，Cl49．4％（calcd．：Ta Concerning the vapor－phase reaction of tan・ 50．51彩，Cl49．49％）．Ammonia was dried by talum pentachloride（TaCl，）with ammoni且，1ittle passing it over sodium hydroxide granules and information has been available apart from the barium oxide powders． work of Hieber夏），who reports that tritantalum 2．2 Experimental proced皿es pentanitride（Ta，N，）films deposit on a fused－ The experimental apparatus used for exami・ silic＆substrate at900～1300℃from a gaseous ning the reaction products of gaseous TaCl， mixture of TaCl，and ammonia at a pressure wlth ammonia is schematically shown in Fig．1． of400torr．However，no information is at pre－ Gaseous TaCl，was formed by heating solid sent available on the reaction process of TaC1， TaC1、（14g）at190℃ and was carried by a with ammonia in the vapor phase． stream of argon（50cm3／min）into the reaction In this paper，the reaction products of gaseous zone （28mm∫．4．，250mm length）held at a TaCI、with ammonia at200～1400。C were ex－ speci且ed temperature． The TaCl、inlet tube amined in detaiL The possible reactions which consisted of two concentric tubes． Gaseous were considered to occur on the basis of the TaCl5cαrried by argon was intro（iuced through above experiments were examined．Further， the inner tube and the outer tube was utilized the thermal stability of the tantalum nitride for introducing argon（50cm3／min）as a sheath formed was examined．The tantalum nitride gas to prevent formation of the reaction prod・ formed was also examined by electron micro－ uct at the chloride inlet tube．Ammonia was scopy・ simultaneously introduced at a How．rate of100 cm3 min into the reaction zone． The mean How－rate of gaseous Tac1、was6．o cm3／min，A ＊Research Laboratory of Resources Utilization，Tokyo quartz or alumina tube was inserted inside the Institute of Technology（4259，Nagatsuta－cho，Mido－ ri・ku，Yokohama227） reaction tube to make the removal of the reac一 677 51，No．8（1983）

spheric moist皿e．

1．ロ／＼ 3． 4． NH5、盲 3 Results and 】Discussion A r→ ウ 3．1 Reaction products of gaseo旦1s tan・司 Ar→ ↑ ↑ ↑ talum pentachloride with ammonia 5． 6、 5． The products formed by heating gαseous TaC15 Fig．1 Experimental apparatus in an ammOnia Stream at VariOUS tem－ 1：TaCl5，2＝Electric fumace，3：Quartz or peratures were examined both by X－ray an＆1・ alumina reaction tube，4＝Quartz or alumina 2）～6）ys1S and chemical analysis。Reaction tem－ inner tube，5＝The㎝㏄ouple，6：Brick or peratures above200。C were employed，because ribbon heater gaseous TaCl，was generated at190。C． tion product easier． The reaction was allowed The product formed at200。C showed a hith－ to proceed for2h， erto unknown X－ray diflraction pattern which The by－product ammonium chloride（NH、Cl） was clearly diflerent from those of ㎞own which deposited outs至de the reaction zone to－ tantalum compounds．The chemical analysis of gether w三th the tantalum nitride formed was the product gave Ta40，8％，C139・9％，NH3 separated by heating the mixture in an argon 19。2％． The ratio of Ta；Cl；NH，was ca正cu・ stream at400℃for10～15h． lated to be1：4．99：5，00．This was considered 2．3 Analy・tical to indicate that tke product formed at2000C The chem孟cal analysis of the reaction product had a composition of TaCl，・5NH、（calcd，＝Ta wαs performed as follows：The tantalum con－ 40．81％，Cl39．98％，NH31921％）。 tent of TaCl，一NH、adduct was gravimetrically The reaction products at various temperatures determined as Ta，0、after hydrolyzing the are shown in Table1．Unreacted TaC15was sample in3M－nitric acid．The chlorine and not observed throughout the temperature range ammonia contents were determined by the gra－ of this work．At500～1000℃，all the products vimetric method as AgCI and by the Kjeldah豆 were obtained outside the reaction zone in the method，respectively，from the Hltrate．In the form of powder．However，at1100～1300℃， case of a mixture of the adduct Emd tantalum in addition to Ta、N，obtained outside the reac・ nitride，the tantalum and chlorine contents were tion zone in the form of powder，Ta2N，θ一 gravimetrically deternlined after the fusion of TaN，andε一TaN were obtained inside the reac－ the sampie with sodium carbonate． Thc NH3 tion zone in the form of film． At14000C， content was determined by the Kjeldahl method Ta、N，θ一TaN，andε一TaN were obtained inside from the丘ltrate after hydrolyzing the sample the reaction zone in the form of mm and small in3M－nitric acid． amomts of Ta4N，，Ta2N，θ一TaN，andε一TaN X－ray analysis of the solid product was per－ were obtained outside the reaction zone in the formed with an X－ray powder diffractometer form of powder．The mole percentage of TaC1， equipped with a proportional counter using Ni converted to the nitrides obねined inside the 五1tered Cu radiation．The sample chamber of the diflractometer was maintained under a dry Table l Reaction products of gaseous TaCl5 nitrogen atmosphere，if necessary，to prevent with ammonia at various temperatures contamination of the sample by atmospheric Temp．／。C Products moisture during the irradiation。 The sensitivity of the quartz helix used for 200 TaCl5・5NH3 250～350 TaC15・5NH5＞Ta3N51NH4Cl thermogravimetry（TG）was approximately94 400 TaCI5・5NH8〉Ta3N51NH4Cl mm／9．The sample（o、29）was heated at a 500 TaC15・5NH3，Ta3N5；NH4CI rate of2．5。C／min and the flow・rate of ammonia 550～600 Ta3N5＞TaC15・5NH3；NHもCl was maintained at50cm3／min． 650｝950 Ta3N51NH4Cl Throughout this work，the TaC1、and the 1000 Ta3N5＞Ta4N51NH4Cl reαction products were handled in an argon 1100～1300 Ta4N5＞Ta2N，θ一TaN，ε一TaNl NH4C1，HCl atmosphere to prevent contamination by atmo・ 1400 Ta2N，θ一TaN，ε一TaN＞Ta4N51NH4Cl，HC1 6．78 DENKI KAGAKU

reaction zone was8％at1100℃，14彩at1200℃， higher than the calculated value，53．92鰯，based 26％at1300。C，and92％at1400℃．Also，HCl on the reaction，3（Taα、・5NH3）十5NH、→Ta3 was formed in addition to NH、Cl above1100℃． N5十15NH4C1． The percentage of HCl formed to the total Therefore，the TaCl5・5NH，（1．O g） in a 「 amount of chlorine introduced as TaCl，was quartz boat（70mm length，15mm width，7mm 10％ at 1100。C，21％at 1200。C，46％ at1300。C， depth）was p｝aced in a stra1ght reaction tube and 96彩 at 1400。C．（28mmガ．4、，1000mm length）．Ammonia was The presence of the following tantalum ni－ introduced into the reaction tube at a How－rate trides have been reported：Ta、N、（tetragona12）・ of 100cm3／min。 The sample part was then ロロ 3）：αo＝10．22g A，60＝3．875A3）or monoclinic： Placed in the centre of an electric furnace （300 α。廻6。廻10．3A，β＝90。3）），Ta、N，（tetragona1： mm heating length）maintained at a specified α・＝6，83。A，6。＝4．272A）3），Ta，N。（hexagona1； temperature for l h．The products obtained α。＝5，17、A，6。＝10．307A）3），θ一TaN（hexagonaL inside and outside the boat were examined by ロロ α。＝2．936A，6。＝2．885A）4），ε一TaN（hexagonal： X－ray amlysis and chemical analysis． The α・＝5．186A，6。＝2．913A）4），Ta、N（hexagona1； results are shown in Table2． α。＝3．0445A，6。＝4．9141A）5），andδ一TaN（cu－ Table2 Exper三mental results for TaC15・5NH3 bic）4）．It was found that the above tantalum 0n heating in an ammonia stream nitrides except Ta5N6andδ一TaN were formed Products Unreac． by the reaction of gaseous TaCI，with ammonia． Heating ted temp，／℃ TaCl5・5 3，2 Reaction process of gaseous tanta・ In the boat Outside the boat NH3 鰯 lum pentachloride with ammonia 250 Ta3N5（8） NH4Cl 92 To elucidate the reaction process of gaseous 300 Ta3N5（69） NH‘Cl 31 TaCls with ammonia，the behavior of the TaC1，・ 350 Ta3N5（81）r NH4Cl 19 5NH、and the Ta、N、，which ha（1been formed 400 Ta3N5（89） TaCl5・5NH3（く1）；NH4Cl 10 during the reaction process， on heating in an 450 Ta3N5（96） TaC15・5NH3（＜1）l NH‘Cl 3 500 Ta3N5（99）・ TaaN5（＜1），TaCI5・5NH3 ammOnia Stream Were eXamined．（く1）；NH4C1 3．2．1BehaviorofTaCI5・5NH30nheat－ Note The value in（）is mole percentage of TaC15・ ing in an ammonia stream The TG curve 5M｛3converted to the product of TaC15・5NH3in an ammonia stream is shown These resu豆ts and the results obtained by in Fig．2．TaC1，・5NH310st weight above235℃。 TG，mentioned above，sHowed that TaC15・5NH、 It was observed that NH、Ci deposited outside reacted with ammonia to form Ta3N5and NH、 the heating zone dur1ng the welght loss． The Cl above about235。C and that a small part of sample after the he＆ting to500。C was found the TaCl、・5NH3vaporized above about400。C。 to be Ta、N， by Xイay analys呈s。 The fiml The formation of a small amount of Ta3N5at weight loss was54．3％r．This value was slightly 500。C outside the boat was considered to1ndi－ cate that the reaction of gaseous TaC1，・5NH3 O with ammonia to form Ta3N，also occurred above about500℃．The slightly higher weight

＆ loss observed during the TG of TaCl，・5NH、＼ 20 詔 compared with the calculated value，as men－ 9 tioned before，was considered to be due to the と

秘40’δ vaporization of TaCl，・5NH、。 3 3．2．2 Behavior of Ta，N50n heati皿g in 60 an ammonia stream The samples obtained by heating Ta3N、（0．2g）in an ammonia stream 200 300 400 500 （100cm3／min）at va「ious temPe「atu「es of900～

Temp．／℃ 1400℃for2h were examined by X－ray anal・ Fig．2 TG curve Qf TaCl5・5NH3 ysis2町5）． The Ta、Ns used was prepared by the in．anammOniaStream reaction of gaseous TaCl、with ammonia＆t 51，No．8（1983） 679

Table3 Products obtained by heating Ta3N5 Then，the reduction of gaseous TaCl、with in an ammOnia Stream hydrogen was examined in similar experimental

Temp．／℃ Products conditions described in2．2，except that hydro－ gen was intro（1uced into the reaction zone in－ → goo Ta3N5 stead of ammonia at the same flow・rate as that 1000 Ta巳N5＞Ta4N5 1100 Ta4N5，Ta5N6 of ammonia．The formation of tantalum by 1200 Ta5N6，θ一TaN，ε一TaN the reduct呈on of gaseous TaCl，with hydrogen 1300 θ一TaN，ε一TaN＞Ta5N6 was observed above about400℃，and the re－ 1400 θ一TaN，ε一TaN duction proceeded markedly above about 700。C to form 亡antalum inside the reaction zone in 800。C，based on the experimental results de－ the form o｛丘1m． Above about1100。C，in scr三bed in3。1．The results are shown in Table addition to the tantalum formed inside the 3． reaction zone，a small amount of t＆ntalum was From the results，it was found that on hea－ obtained outside the reaction zone in the form ting Ta，N，in an ammonia stream，Ta3N，decom－ of powder． posed above about 1000。C and thatθ一TaN Next，the products obtained by heating tan－ andε一TaN were formed above about1200℃ talum（1．Og）in a nitrogen and in an ammonia u宛Ta、N，and Ta，N。． stream（100cm3／min）at va「ious temPe「atu「es Based on the above experimental results，the of900～1400。C for2h were examined by X－ reaction process of gaseous TaC1，with ammonia ray ＆naiysis4・5・9）． The experimental results was discussed． As shown in Table1，TaC15・ in a nitrogen stream are shown in Table4。It 5NH。alone was formed at200℃．This fact was found thatθ一TaN andε一TaN were formed indicates that the reaction of TaC1，with am・マ，魏Ta，N by the nitriding of tantalum both in monia to form TaC15・5NH30ccurs丘rst． The a nitrOgen Stream and in an ammOnia Stream． Ta，N，formed at250～1000。C is considered to Table4 Products obtained by heating be due to the reaction of TaC1、・5NH、with tan亡al㎝inani亡rOgens亡ream ammonia，because the TaC15・5NH、reacts with Products ammonia above about235。C to form Ta、N，，as Temp．ノ℃ described above． The Ta、N、formed above goo Ta2N＞θ一TaN，Ta 1000DC is considered to be due to the decom・ 1000 Ta2N〉θ一TaN，ε一TaN 1100 θ一TaN，ε一TaN＞Ta2N FUo二し■）晶）ム ⊥“3ム■5， μヤ｝、んu一）｝一一一一5南・D 一一一n（σlf；＾ハ（‘Tqへ1 トρρqllqρ砧ρ丁月N．命mm・ 1200～1400 θ一TaN，ε一TaN poses above about1000。C to form T＆、N、． Above 1100℃，Ta2N，θ一TaN，and 6－TaN Based on the above exper三mental results，the were formed in addition to Ta、N。and NH、C1， formation processes of the Ta、N，θ一TaN，and and HCI was also formed，as shown in Table ε一TaN，which were formed above 1100。C by 1。The percentage of the HCI forme（i，de・ the react呈on of gaseous TaCl。with ammonia， scribed in3．1，is considerably higher than that were discussed．As seen from the results shown of HCI formed by the thermal decomposition in Tables3and4，Ta、N was not formed by－ of NH、Cl at each temperature under the ex－ the thermal decomposit圭on of Ta、N，but formed perimental conditions in this work7）．Also，the by the nitr…ding of tantalum． The fact was thermal dissociation of ammonia under the ex－ considered to indicate that the formation of perimental conditions in this work proceeds Ta2N was due to the nitriding of the tantalum markedly above about1100℃to form hydrogen resulting from the hydrogen reduct至on of TaC15． and nitrogen7）．Considering these facts，it was The formation ofθ一TaN andε一TaN was con・ considere（i that the reduction1～8） of gaseous sidered to be due to the thermal decomposition TaC1，with hydrogen resulting from the thermal of Ta3N，or the nitriding of tantalum．From dissociation of ammonia also occurred to form the fact thαt Ta、N，，which was formed during tantalum and HCI and that the tantalum formed the therma生decomposition of Ta、N，，was not reacted with nitrogen or ammonia to form t＆n－ formed by the reaction of gaseous Taα，with talum nitrides． ammonia（Table1），it was considered thatθ一 680 DENKI KAGAKU

TaN and ε一TaN were formed also by the 段nd then toθ一TaN andε一TaN at1300～1400℃． nitriding o至tantalum．As described in3．1，θ一 Finally，the tantalum nitrides obtained outside TaN andε一TaN were obtained ins玉de the reac－ the reaction zone by the reaction of gaseous tion zone together with Ta、N in the form of TaC1，with ammonia at various temperatures 五lm．This was considered to support the above－ were examined by electron microscopy．The mentioned estimation thatθ一TaN andε一TaN typical micrographs of the tantalum nitride are was formed by the nitriding of the tantalum shown in Fig、3。丘1ms resulting from the hydrogen reduction of gaseous TaC15． From the above－mentioned results，the forma・ tion process of tantalum nitride by the vapor－ phase reaction of TaCI、with ammoni＆can be represented as follows：The reaction of gaseous TaCl、with ammonia occurs丘rst to form TaC1，・蟄 5NH3． Above about235。C，the TaCl5・5NH3 a） 11000C C reacts with ammonia to form Ta、N5．Above Fig．3 Electron micrographs of the tantalum about1000。C，the Ta，N，decomposes to Ta、N5． nitrides formed at various temperatures Above about1100。C，玉n addition to these reac－ tions，the nitriding of tantalum，formed by the As seen from Fig．3，the tantalum nitrides reduction of gaseous TaC1， with hydrogen formed above1200。C under the experimentaI resulting from the thermal dissociation of am－ conditions in this work were uniform，ultrafine monia，also occurs to form Ta2N，θ一TaN，and powders with the particle diameters of the ε一TaN．・rder・f1／10伽m， 3．3 Properties of the tantalum nitride Acknowle－gement： forme4 The present work was partially supported by a To obtain㎞owledge on the thermal stability Grant－in－Aid for Scienti丘c Research No．56470058 fro皿the Ministry of Education，Science and Culture． of the tantalum nitride formed by the reaction of gaseous TaC1、with ammonia，the Ta3N， Reference8： K．Hieber，Tん∫7z30あ4F㍑ηz5，24，157 （1974）．1）（0．2g），formed at800℃，was heated in an 2） JCPDS，Powder Diffraction File19－1291． argon atmosphere at various temperatures for 3） N．Terao，」‘ψ㈱」．イ4ρμ．Phy5．10，248（1971）。 2h． X－ray analysis of the samples obtained G．Brauer and E．Mohr－Rosenbaum，Mo襯‘5h．Ch8綱．4） after the heating showed them to be unchanged 102， 1311 （1971）． JCPDS，Powder Diffraction File29－1321．5） Ta3N5at800。C，Ta3N5＞Ta4N5at900℃，Ta4N5 ASTM，Powder Di狂raction File7－7．6）＞Ta3N5at1000。C，T＆4N5，θ一TaN，ε一TaN＞ Y．Saeki，R．Matsuzaki，A．Yaj1ma，and M．Aki－7） TasN6at1100℃，θ一TaN＞ε一TaN， Ta5N6at yama，B躍．Cんε隅．Soc．Jl砂㈱55，3193（1982）． 1200。C，and θ一TaN＞ε一TaN at1300～1400℃． 8） R．Young and C．Brubaker，」．A窺．Cん8規．Sαン。74， 4967 （1952）． From these results，Ta、N5was stable below 9）ASTM，X－Ray Powder Data Fiie4－788， 800。C and it changed to Ta、N，at about900。C， 3，19831Accepted Apr、28，1983）（Recelved Mar to Ta5N6りθ一TaN，andε一TaN at about1100。C，

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