Y2(Te4O10)(SO4): a new sulfate tellurite with a unique Te4O10 polyanion and large birefringence

Abstract

Two new yttrium sulfate tellurites, namely, Y₃(TeO₃)₂(SO₄)₂(OH)(H₂O) and Y₂(Te₄O₁₀)(SO₄), were achieved in our exploration of new sulfate tellurites, with a large birefringence in the Y³⁺–Te⁴⁺–SO₄²⁻ system. The two compounds exhibit two new three dimensional (3D) frameworks composed of different yttrium tellurite layers bridged by sulfate tetrahedra. The tellurite groups in Y₂(Te₄O₁₀)(SO₄) polymerized together into a unique (Te₄O₁₀)⁴⁻ 1D double-strand with an eight-member polyhedral ring tunnel along the a-axis. Optical diffuse reflectance spectra showed that the two compounds present a wide energy band gap with Eg values of 4.4 and 4.1 eV respectively. The birefringence values of Y₃(TeO₃)₂(SO₄)₂(OH)(H₂O) and Y₂(Te₄O₁₀)(SO₄) were calculated to be 0.092 and 0.149 at 532 nm respectively. Furthermore, the anhydrous Y₂(Te₄O₁₀)(SO₄) features a large birefringence, wide energy band gap and high thermal stability. In addition, the IR spectrum, TG-DSC curve and theoretical calculations of the title compound were recorded in this paper.