A_2W_3O_(12)(A=Y,Er,Ho,Yb)型稀土钨酸盐的高温XRD研究及结构精修

High-Temperature XRD Study and Rietveld Refinement of A_2W_3O_(12)(A=Y, Er, Ho, Yb) Rare-Earth Tungstate

用高温固相反应法制备出A2W3O12型稀土钨酸盐材料(A=Y,Er,Ho,Yb),用室温及高温XRD测定其在不同温度下的结构、晶胞参数及晶胞体积,并用TOPSA软件对其结构进行精修。发现除Ho2W3O12外,都具有较大的负热膨胀系数。据A.W.Sleight预测,Ho2W3O12具有较大的负热膨胀特性,但本实验却发现它并没有负热膨胀性,反而具有非常大的正热膨胀系数。

A2W3O12（A=Y, Er, Ho, Yb） rare-earth tungstate materials were synthesized by solid state method at high temperature. The structures, lattice constants and cell volumes of A2W3O12 were determined by room temperature and high temperature XRD at different temperatures, and their Rietveld refinements were performed by TOPAS software. It is found that Y2W3O12, Er2W3O12 and Yb2W3O12 all possess orthorhombic structure and show negative thermal expansion; whereas Ho2WaO12 has monoclinic structure and shows positive thermal expansion. According to A. W. Sleight prediction, Ho2W3O12 should have large negative thermal expansion, but it shows no negative thermal expansion but large positive thermal expansion coefficient in the present experiment.