〔（NH_4）_xK_（1－x）〕_2SnCl_6混晶的喇曼散射研究  

Raman Scattering Studies of Mixed Crystals (NH_4)_xK_(1-x) _2SnCl_6

作　　者：沈军[1] 徐永晨[1] 

机构地区：[1]同济大学玻耳固体物理研究所

出　　处：《光谱实验室》1994年第1期26-29,共4页Chinese Journal of Spectroscopy Laboratory

摘　　要：本文用喇曼散射的方法研究了六氯锡化钾铵混晶系列样品［（ＮＮ_４）_ｘＫ_（１－ｘ）］_２ＳｎＣｌ_５（ｘ＝０，０．０５，０．１，０．１５，０．２，０．２５，０，３，１）从室温到７７Ｋ的行为，首先观察到了其外振动模的双模行为，并且还发现了其一内模Ｔ_（２ｇｉｎｔ）的宽度随铵离子浓度ｘ的增加而增加，相变温度Ｔｃ却随铵离子浓度的增加而迅速下降，下降速率约为ｄＴ_ｃ／ｄｘ＝－６００Ｋ／ｍｏｌ，这一行为是由于正四面体的ＮＨ_４￣＋离子对正八面体的ＳｎＣｌ_６￣（２－）离子团的转动产生阻碍而引起。内模Ｔ_（２ｇｉｎｔ）的宽度变化也是由于铵离子的转动影响以及由它引起的晶格畸变所导致。双模行为来自于强烈的集团效应。Raman scattering studies have been made for mixed crystals [(NH_4)_xK_(1-x)]_2SnCl_6 with x=0, 0. 05 , 0. 1, 0. 15 , 0. 2, 0. 25 , 0. 3 and 1 , temperature ranging from room temperature down to 77K. The spectra show a two─mode behavior for external mode, and one of the internal modes T_(2gint) widened with the increase of the NH_4￣+ concentration x. The phase transition temperature T_c decreased with the increase of x at a rate of about dT_c/dx=-600K/mol. This is due to the blocking of the tetrahedral NH_4￣+ to the rotation of the SnCl_6￣(2-) octahedra. The concentration dependence of the width of T_(2gint) is originate from the static distortion of the lattice which lifts the three-fold degenerancy and the influence of the rotational motion of the NH_4￣+ substituents. The two─mode behavior of the external modes may come from the strong clustering effect.

关 键 词：混晶 喇曼光谱 铵 六氯锡化钾铵 

分 类 号：O614.113[理学—无机化学]