LnV₃Te₃O₁₅(OH)₃·nH₂O (Ln = Ce, Pr, Nd, Sm, Eu, Gd; n = 1-2): a new series of semiconductors with mixed-valent tellurium (IV,VI) oxoanions.

Abstract

Six new lanthanide tellurium vanadates with the general formula LnV3Te3O15(OH)3·nH2O (LnVTeO) (Ln = Ce, Pr, Nd, Sm, Eu, and Gd; n = 2 for Ce and Pr; n = 1 for Nd, Sm, Eu, and Gd) have been prepared hydrothermally via the reactions of lanthanide nitrates, TeO2, and V2O5 at 230 °C. LnVTeO adopts a three-dimensional (3D) channel structure with a space group of P63/mmc. Surprisingly, two types of oxoanions: Te(IV)O3(2-) trigonal pyramids and Te(VI)O6(6-) octahedra, coexist in these compounds. Solid-state UV-vis-NIR absorption spectra for LnVTeO show approximate band gaps on the order of 1.9 eV, suggesting the wide band gap semiconducting nature of these materials. No magnetic phase transition was observed in any of the analogues, but a clear increase in the strength of short-range antiferromagnetic correlations was found with the shortening of distances between magnetically coupled Ln(3+) ions in LnVTeO.