Sr5TeO2(BO3)4 and NaSr5(BO3)(SiO4)2: two inorganic metal borate derivatives with diverse zero dimensional anions

Two new inorganic metal borate derivatives, Sr5TeO2(BO3)4 and NaSr5(BO3)(SiO4)2, have been obtained through a high temperature solid reaction method. Sr5TeO2(BO3)4 crystallizes in a tetragonal space group of P4/mnc featuring a three-dimensional (3D) structure composed of a porous 3D strontium framework stabilized by the unique zero-dimensional (0D) [TeO2(BO3)4]10− anions. NaSr5(BO3)(SiO4)2 crystallizes in a monoclinic space group of P21/c with a 3D structure consisting of a splendid strontium 3D framework strengthened by isolated BO3 and SiO4 groups. The sodium cations located in the empty space of the structure. Thermal stability analyses, optical property measurements and theoretical studies of the compounds were performed. Refractive index calculations revealed that the birefringence of Sr5TeO2(BO3)4 and NaSr5(BO3)(SiO4)2 is 0.048 and 0.029, respectively, at 1064 nm.