（Nb_yTi_（1－y））C_x单晶体制备及其结构研究

用熔剂法制备了（Ｎｂ＿ｙ．Ｔｉ＿（１－ｙ））Ｃ＿ｒ单晶体，用Ｄｅｂｙｅ照相法及四圆衍射仪对其晶体结构进行了研究。实验结果表明，（Ｎｂ＿ｙＴｉ￣（１－ｙ）Ｃ＿ｘ中存在类似于作化学计量化合物ＴｉＣ＿ｘ及ＮｂＣ＿ｘ的有序一无序转变现象，转变温度随其化学成份改变在１１７５～１２８０Ｋ范围内变化。高温型（Ｎｂ＿ｙＴｉ￣（１－ｙ））Ｃ＿ｘ的晶体结构属ＮａＣｌ型结构，碳空位呈随机分布；低温型（Ｎｂ＿ｙＴｉ￣（１－ｙ））Ｃ＿ｘ的晶体中碳空位呈短程有序分布，可用Ｖ＿６Ｃ＿５晶体结构模型进行描述。

STUDY ON PREPARATION AND CRYSTAL STRUCTURE OF (Nb_yTi_(1-y))C_x

Single crystal of high melting-point compound,(Nb_yTi_(1-y))C_x , was prepared by using the fluxmethod, and its crystal structure was studied by Debye X-ray photography and four-cycle single-crystaldiffractometer. Experiment results show that there exists order-disorder phase transition in the(Nb_yTi_(1-y))C_xReceived:November 20. 1993.Correspondent:Zha Congji,National Laboratory of Advanced Technology on Material Processing,Wuhan University of Technology,Wuhan 430070.crystal as that in TiC_x and NbC_x,and the phase transition temperature can be varied from 1175K to 1280Kwith the change of its chemical composition. The crystal structure of(Nb_yTi_(1-y))C_x of high temperature phasehelongs to NaCl-type structure,and its carbon vacancy distribution is in disorder.However,the structure of(Nb_yTi_(1-y))C_x of low temperature phase is an ordered structure,its carbon va cancy dlstribution is nearly in order and the structure may be discribed by the V_6C_5 structure model.