Synthesis and structural study of a new group of trigermanates, CaRE2Ge3O10 (RE = La–Yb)

Abstract

A new series of germanates CaRE₂Ge₃O₁₀ (RE = Y, La–Yb) has been prepared using an EDTA-assisted route. Rietveld refinement of room temperature powder X-ray diffraction patterns shows that these compounds crystallize in the monoclinic system (S.G. P2₁/c, Z = 4) and have two morphotropic transitions. The calcium and rare earth atoms are distributed among three nonequivalent sites and form layers along the [0 0 1] direction connected into the framework through [Ge₃O₁₀]. The morphotropic transitions are accompanied by changes in the site occupancy factors of metal cations and by variation in the first and second coordination spheres of Ca²⁺/RE³⁺.