NdCl_3-LiCl及NdCl_3-LiCl-NaCl体系相图的研究

An Investigation on Phase Diagram of Systems NdCl_3-LiCl and NdCl_3-LiCl-NaCl

利用DTA和X射线结构分析研究了NdCl_3-LiCl二元体系相图和NdCl_3-LiCl-NaCl三元体系液相限。发现NdCl_3-LiCl体系相图属于简单低共熔型,低共熔点e3为28.5(wt％)LiCl,452℃。在低共熔温度以下有一固相下生成的介稳化合物,在443℃分解,组成为2NdCl_3·LiCl。经长时间退火,该化合物消失。NdCl_3-LiCl-NaCl体系有对应NdCl_3、NaCl、2NaCl·LiCl、NaCl·LiCl的五个液相面,七条两次结晶线,一个三元低共熔点E[69.0(wt％)NdCl_3,13.5(wt％)NaCl,374℃],两个三元转熔点P_1[69.5(wt％)NdCl_3,14.5(wt％)NaCl,380℃],P_2[70.0(wt％)NdCl_3,15.5(Wt％)NaCl,385℃]。对应的三个四相平衡反应为 L?NdCl_3+LiCl+NaCl·LiCl E L+2NaCl·LiCl?NdCl_3+NaCl·LiCl P_1 L+NaCl?NdCl_3+2NaCl·LiCl

The phase diagram of systems NdCl_3-LiCl and NdCl_3-LiCl-NaCl have been investigated by means of DTA and X-ray diffraction. It was found that the phase diagram of binary system NdCl_3-LiCl is eutectic type with eutectic point e_3[28.5(wt%)LiCl, 452℃]. A metastable compound, LiNd_2Cl_7 was shown to form in the solid state with temperature of decomposition at 443℃. There are 5 surfaces corresponding to the primary crystallization of NdCl_3, LiCl, NaCl, LiNa_2Cl_3 and LiNaCl_2 respectively and 7 univariant lines relabed to the secondary crystallization in the system NdCl_3-LiCl-NaCl. The temperature of the ternary eutectic E, composed of [69.0 (wt%)NdCl_3, 13.5(wt%)NaCl], was found to be 374℃. The temperature of the ternary peritectics P_1 and P_2, composed of [69.5(wt%)NdCl_3, 14.5(wt%)NaCl]and[70.0(wt%) NdCl_3, 15.5(wt%)NaCl], were shown be be 380℃ and 385℃ respectively.