Crystal Structures of Dy_2(WO_4)_3 and GdY(WO_4)_3

摘要

Two compounds, Dy2(WO4)3 and GdY(WO4)3; were synthesized by using the standard solid state reaction tech-nique. The crystal structure was determined by powder X-ray diffraction and Rietveld refinement method. It is found thatboth compounds have Eu2(WO4)3-type monoclinic structure, with space group C 2/c, Z = 4. The unit cell parameters ofDy2(WO4)3 are a = 0.75981(1) nm, b = 1.13220(1) nm, c = 1.13254(1) nm, and β= 109.8001(3)°, and those of GdY(WO4)3are a = 0.76175(1) nm, b = 1.13543(1) nm, c = 1.13496(2) nm, and β= 109.8015(13)°. Each W atom has four oxygen near-est neighbors, while each rare-earth atom is surrounded by eight oxygen atoms. WO4 tetrahedra share their four verticeswith REO8 (RE = Dy, Gd, or Y) trigondodecahedra and some REO8 trigondodecahedra share an edge with each other. Thephase transition and the magnetic properties were investigated by differential thermal analysis (DTA) and dc superconduct-ing quantum interference device (SQUID) magnetometer.