Gd_xTm_(2-x)W_3O_(12)(x=0.5,1,1.5)的制备和负热膨胀性的研究

Synthesis and Thermal Expansion Properties of Gd_xTm_(2-x)W_3O_(12)(x =0. 5,1,1. 5)

在GdxTm2-xW3O12（x=0.5,1,1.5）系列固溶体中,当Gd的含量较低（x=0.5）时,其室温稳定相为正交相;当Gd的含量较高（x=1,1.5）时,其室温稳定相为单斜相,但在高温时转变为正交相。采用高温淬火的方法,使GdxTm2-xW3O12（x=0.5,1,1.5）高温时的正交相保留至室温。通过TG-DSC和高温XRD研究了其吸水、相变和热膨胀性,结果表明：当x=0.5时,Gd0.5Tm1.5W3O12的吸水性较弱,而当x=1和1.5时,其吸水性增强;GdxTm2-xW3O12（x=0.5,1,1.5）在500℃以下,其正交相是稳定的;GdxTm2-xW3O12（x=0.5,1,1.5）在200-500℃的区间均具有较大的负热膨胀性,并且其负热胀系数随着Gd的含量增加而增大。

The solid solutions of GdxTm2-xW3O12（x=0.5,1 and 1.5） were successfully synthesized by solid state method and quenching. Their structures, hydroscopicity, phase transition and thermal expansion properties were studied by XRD, TG-DSC and high temperature XRD. It was found that Gd0.5Tm1.5W3O12 was in orthorhombic phase, GdTmW3O12 and Gd1.5Tm0.5W3O12 were in monoclinic phase at room temperature. However, GdTmW3O12 and Gd1.5Tm0.5W3O12 were in orthorhombic phase at high temperature. Through high temperature quenching, the orthorhombic phase of GdTmW3O12 and Gd1.5Tm0.5W3O12 were remained in room temperature. The thermal stability and thermal expansion properties of them were investigated. The coefficient of thermal expansion increases along with the increasing of Gd contents.