BaCuSiTe3: A Noncentrosymmetric Semiconductor with CuTe4 Tetrahedra and Ethane-like Si2Te6 Units

Abstract

BaCuSiTe₃ was prepared from the elements in a solid-state reaction at 973 K, followed by slow cooling to room temperature. This telluride adopts a new, hitherto unknown structure type, crystallizing in the noncentrosymmetric space group Pc with a = 7.5824(1) Å, b = 8.8440(1) Å, c = 13.1289(2) Å, β = 122.022(1)°, and V = 746.45(2) ų (Z = 4). The structure consists of a complex network of two-dimensionally connected CuTe₄ tetrahedra and ethane-like Si₂Te₆ units with a Si-Si bond. This semiconducting material has an optical band gap of 1.65 eV and a low thermal conductivity of 0.50 W m^-1 K^-1 at 300 K. Calculations of its optical properties revealed a moderate birefringence of 0.23 and a second-order harmonic generation response of d_eff = 3.4 pm V^-1 in the static limit.