Synthesis and Characterization of the New Lead Strontium Germanate PbSrGeO_4

摘要

The new lead strontium germanate PbSrGeO_4 was synthesized by a high-temperature solid-state reaction of lead(II) oxide, strontium carbonate, and germanium(IV) oxide at a temperature of 900 °C in a platinum crucible. The compound crystallizes in the orthorhombic space group P2_12_12_1 (no. 19) being isotypic to the structure of BaNdGaO_4 [1]. The primitive cell contains four formula units with lattice parameters of a = 995:40(2), b = 732:44(2), c = 599:42(2) pm, V = 437:02(2)?~3, and residuals of R_1 = 0:0385 and wR_2 = 0:0997 for all data. The main structural element of PbSrGeO_4 is an isolated [GeO_4]~(4-) tetrahedron. A circular arrangement of six of these [GeO_4]~(4-) tetrahedra leads to the formation of large channels along b in which the strontium cations are eightfold coordinated by oxygen atoms. The lead cations are coordinated by three oxygen atoms, and with a lone pair of electrons they show a pseudo-tetrahedral coordination. Next to the structural investigations, PbSrGeO_4 was characterized by Raman-spectroscopic investigations and DFT calculations.