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

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.