Studies on triple orthovanadates. Part 3. Crystal chemistry of the zircon analogues of type MIILnMIV(VO4)3(MII= Ca or Pb; MIV= Ce or Th; Ln = lanthanide element)

Abstract

The solid-state synthesis and crystallographic characterization of some triple orthovanadates with general formula M^IILnM^IV(VO₄)₃(M^II= Ca or Pb; M^IV= Ce or Th) are presented. The compounds are found to crystallize with a tetragonal unit cell of space group I4₁/amd and are isostructural with lanthanide orthovanadates (LnVO₄) having the zircon structure. Attempts are made to explain the stability range of the zircon structure on the basis of average ionic radii of substituting cations in the present group of triple orthovanadates.