La_2NiO_(4.147)体系相变的低频内耗  

PHASE TRANSITION IN La2NiO4.147 SYSTEM STUDIED BY LOW-FREQUENCY INTERNAL FRICTION TECHNIQUE

作　　者：张华力[1] 刘卫[1] 苏金瑞[1] 丁锦文[1] 陈初升[1] 

机构地区：[1]中国科学技术大学材料科学与工程系内耗与固体缺陷实验室,合肥230026

出　　处：《金属学报》2003年第11期1157-1159,共3页Acta Metallurgica Sinica

摘　　要：通过电化学加氧方法获得额外氧含量δ=0.147、结构为Fmmm的La2NiO4+δ样品.低频内耗测量表明,400K温区附近存在一个相变内耗峰,它对应体系从低温正交Fmmm相到高温四方I4/mmm相的转变,模量和内耗的升、降温回滞现象反映此相变为一级相变.变频和改变升温速率内耗实验表明,内耗峰高与测试频率成反比,与升温速率成正比,具有马氏体相转变特征.低δ值的La2NiO4+δ样品无此相变峰,说明此峰应与低温正交Fmmm相中额外氧的三维有序变化相关.La2NiO4.147 sample with Fmmm symmetry is prepared by electrochemical oxidation process. It is found that there exists a low-frequency internal friction peak around 400 K with phase transition character, which just located in the position of one phase transition, reported by literature, from the low temperature orthorhombic Fmmm phase to high temperature tetragonal I4/mmm phase. The thermal hysteresis of the modulus and internal friction in heating and cooling processes as well as the fact that height of the internal friction peak is proportional to the rate of the heating and reciprocal to the work frequency mean that this phase transition belongs to a first order phase transition with martensitic type. No such phase transition observed in low delta sample of La2NiO4+delta suggests the above phase transition may have relationship with the three-dimensional ordering of excess oxygen in the low temperature orthorhombic Fmmm phase.

关 键 词：La2NiO4 额外氧 低频内耗 马氏体相变 

分 类 号：TG113.226[金属学及工艺—物理冶金]