Li Caifu

Structural Ordering and Magnetic Property of Complex Perovskite Solid Solution (1−x)Pb(Fe2/3W1/3)O3-xPb(Mg1/2W1/2)O3

Pb(Fe2/3W1/3)O3 was modified by doping Pb(Mg1/2W1/2)O3 with Sol-Gel method using inorganic salts as precursors.At calcination temperature of 700℃,the resulted solid solution(1-x)Pb(Fe2/3W1/3)O3-xPb(Mg1/2W1/2)O3 kept a perovskite structure in the whole doping range of 0≤x≤1.The obtained Pb(Mg1/2W1/2)O3(x=1) is fully or-dered with a unit cell as two times as that of Pb(Fe2/3W1/3)O3(x=0).Solid solution(1-x)Pb(Fe2/3W1/3)O3-xPb(Mg1/2W1/2)O3(0x1.0) also has an ordered crystal structure showing supperlattice peaks of 1/2(111) and 1/2(311) in X-ray diffraction,whose intensities become stronger as x increases.Combining electron diffraction and elemental analysis in transmission electron microscope,solid solution(1-x)Pb(Fe2/3W1/3)O3-xPb(Mg1/2W1/2)O3 is verified as a single phase with perovskite structure,rather than a mixture of two phases.The particles of solid solu-tion have a cubic morphology,and their grain size first decreases and then increases when doping coefficient x var-ies from 0.2 to 0.8.Due to the substitution of larger Mg2+ for smaller Fe3+ ions,its lattice constant increases linearly with the enhancement of x.According to the measured M-H curves,the magnetic performance of the solid solution decays as the doping coefficient x increases,because the formation of diamagnetic Pb(Mg1/2W1/2)O3 could destroy the -Fe3+-W-O-W-Fe3+- and -Fe3+-O-Fe3+- magnetic bonds in antiferromagnetic Pb(Fe2/3W1/3)O3 phase.以无机盐为前驱体, 利用溶胶?凝胶法固溶合成了(1- x )Pb(Fe 2/3 W 1/3 )O 3 - x Pb(Mg 1/2 W 1/2 )O 3 多铁性固溶体. XRD分析表明, 在0≤ x ≤1.0的掺杂范围内, 700℃煅烧所得产物都具有钙钛矿结构; x =0时得到的纯Pb(Fe 2/3 W 1/3 )O 3 为长程无序结构, x =1.0时可获得完全有序的纯Pb(Mg 1/2 W 1/2 )O 3 相, 其单胞为Pb(Fe 2/3 W 1/3 )O 3 单胞的2倍; 当0 x x )Pb(Fe 2/3 W 1/3 )O 3 - x Pb(Mg 1/2 W 1/2 )O 3 固溶体也为有序结构, 出现1/2 (111)及1/2 (311) XRD衍射峰, 且强度随掺杂系数x的升高逐渐增大. TEM分析证实, 煅烧产物为具有钙钛矿结构的单相固溶体, 而非两相复合物; 固溶相形貌以立方颗粒为主, 随掺杂量增加其晶胞常数线性增大, 而晶粒尺寸先减小后变大. 性能测试发现, 固溶相的磁学性能随x的增加而逐渐下降, 起因于抗磁性的Pb(Mg 1/2 W 1/2 )O 3 破坏了Pb(Fe 2/3 W 1/3 )O 3 原有的价键结构所致.