STRONTIUM TELLURITE

Description

Strontium tellurite has the molecular weight of 215.6761 g/mol and the molecular formula of SrTeO3. It can be formed via the solid-state reaction:
SrO+ TeO2+ heat ? SrTeO3
An inert atmosphere is required. This salt is a metatellurite. If a solution method is used, a monohydrate is formed:
SrCl2+ Na2TeO3 ? SrTeO3·H2O+ 2NaCl
Additionally, this compound can be prepared by reacting tellurium dichloride in a solution of strontium chloride:
SrCl2+ 2TeCl2+ 3H2O ? Te+ SrTeO3·H2O+ 6HCl

Physical properties

In all cases involving solution chemistry, the product is a monohydrate. Its CAS number is 13812-57-2 and its molecular weight is 233.6915 g/mol. Strontium tellurite (SrTeO3) has been shown by Yamada and Iwasaki (1972) to possess ferroelectric properties (ferroelectric = a substance exhibiting permanent electric polarization that varies in strength with the applied electric field).
The crystal structure of strontium tellurite, SrTeO3, has been determined at roomtemperature using X-ray diffraction data obtained from single crystals grown by the Czochralski method. Selection of a noncentrosymmetric (C2) structure model was confirmed by the second harmonic generation (SHG) test. The structure of strontiumtellurite is built up of three types of distorted [SrO_x] polyhedra (x=6, 7 and 8) that share their oxygen anions with TeO3 pyramidal units. These main anionic polyhedra are responsible for establishing two types of tunnels required for the electron lone pairs of the Te⁴⁺ cation.
In another systematic investigation of strontium tellurite, SrTeO3, with particular emphasis on crystal chemistry and phase transitions, the structure of the γ-phase has been determined at 583 K using a single-crystal analysis. Both structural and nonlinear optical measurements indicate a β?γ first-order phase transition temperature that is close to 563 K. The structure of the γ-phase is monoclinic (C2) and does not differ essentially from the a-phase (C2). Comparison of the α and γ structures shows that the main atomic shifts and tilting are connected with Te₄, Te₅ and Te₆ pyramids.

Preparation

Aluminate sodalites containing the telluride and tellurite ions have been synthesized for the first time. The structures of Sr8[AlO2]12(TeO3)2 and its reduced product Sr[AlO2]12Te2 have been determined using Rietveld refinement of powder neutron-diffraction (PND) data. In Sr8[AlO2]12Te2, the anion occupies a position at the sodalite cage center, while in Sr8[AlO2]12(TeO3)2 the larger tellurite ion is displaced to allow reasonable coordination to the strontium ions.
Sr_1-x PbxTeO3 (0 < x < 0.2) and Sr_1-xLa_2xTe_1+2xO_3+6x (0 < x < 0.15) solid solutions are synthesized (the latter, for the first time), and their properties are studied. The results demonstrate that partial substitutions of Pb and La for Sr extend the temperature stability range of ferroelectric SrTeO3.
Although a number of research papers have been published, its usage in industry is miniscule. It is, however, available commercially by several manufacturers.