LiF-ZrF_(4)熔盐体系离子结构的Raman光谱

Raman Spectroscopy on Ionic Structure of LiF-ZrF_(4) Molten Salt System

采用Raman光谱和量子化学计算相结合的方法,研究了803~1 086 K下,ZrF_(4)摩尔分数为10%~60%的LiF-ZrF_(4)熔盐体系的离子结构特征及变化规律.研究结果表明:熔体中含有ZrF_(5)^(-),ZrF_(6)^(2-),ZrF_(7)^(3-)和ZrF_(8)^(4-)四种络合阴离子团,其中以ZrF_(7)^(3-)和ZrF_(8)^(4-)为主,二者摩尔分数之和高达90%~94%,ZrF_(5)^(-)和ZrF_(6)^(2-)含量较少.在熔盐升温初始阶段,熔盐中发生ZrF_(7)^(3-)与ZrF_(6)^(2-)生成ZrF_(8)^(4-)和ZrF_(5)^(-)的反应(ZrF_(7)^(3-)+ZrF_(6)^(2-)→ZrF_(8)^(4-)+ZrF_(5)^(-));到达一定温度后,熔盐中发生ZrF_(8)^(4-)与ZrF_(6)^(2-)生成ZrF_(7)^(3-),ZrF_(5)^(-)和F-的反应(ZrF_(8)^(4-)+ZrF_(6)^(2-)→ZrF_(7)^(3-)+ZrF_(5)^(-)+2F-).随着ZrF_(4)质量分数增加,熔盐中ZrF_(5)^(-)含量增加,ZrF_(6)^(2-),ZrF_(7)^(3-)和ZrF_(8)^(4-)的含量减少.

The Raman spectroscopy and quantum chemistry calculations were employed to analyze the ionic structure and variation rule of the LiF-ZrF_(4)molten salt system with the molar fraction of ZrF_(4)ranging from 10%to 60%at 803~1086 K.The study identified four complex ions in the molten salts:ZrF_(5)^(-),ZrF_(6)^(2-),ZrF_(7)^(3-),and ZrF_(8)^(4-).In the molten salts,ZrF_(7)^(3-)and ZrF_(8)^(4-)are the major components,accounting for 90%~94%,while ZrF_(5)^(-)and ZrF_(6)^(2-)are present in lower amounts.At the initial stage of temperature increase,a reaction between ZrF_(7)^(3-)and ZrF_(6)^(2-)occurs,producing ZrF_(4)-8 and ZrF^(-)_(5)(ZrF_(7)^(3-)+ZrF_(6)^(2-)→ZrF_(8)^(4-)+ZrF^(-)_(5)).At a certain temperature,a reaction between ZrF_(8)^(4-)and ZrF_(6)^(2-)takes place and produces ZrF_(7)^(3-),ZrF^(-)_(5),and F-(ZrF_(8)^(4-)+ZrF_(6)^(2-)→ZrF_(7)^(3-)+ZrF_(5)^(-)+2F^(-)).With the increase of ZrF_(4),the amount of ZrF_(5)^(-)increases,while the amounts of ZrF_(6)^(2-),ZrF_(7)^(3-),and ZrF_(8)^(4-)decrease.