Physicochemical properties of CuR(WO4)2 double tungstates

The results of X-ray diffraction study, optical analysis and infrared spectroscopy of CuR(WO4)2 (R=La-Lu, Y) tungstates, synthesized by the solid-phase method at 550-10O0 deg during 32 h in stationary argon or helium flows with 0.9-1.3 Pa partial oxygen content are given. In CuR(WO4)2 series four structural types were revealed, two of which, d-LiPr(WO4)2 (R=Tb-Er) and NaIn(WO4)2 (R=Ho-Lu) - are known, others, #betta#-CuPr(WO4)2 (R=Ce-Na) and Eu2(WO4)3-d2 (R=La-Gd), have no known analogs. In the case, when R=Dy, Ho, Er, Lu, the existence of isotypical and isostructural phases in discrete temperature ranges was revealed. Tungstates investigated are characterized by distorted to a varied degree octahedral tungsten coordination in regard to oxygen. On heating in inert medium all phases (except CuCe(WO4)2) are decomposed in solid state