Oxidation of bismuth tellurite, Bi_2TeO_5 I.Thermoanalytical and optical microscopic studies

摘要

Deatalied thermoanalytical experiments were carried out to reveal the oxidative and reductive processes in the Bi_2TeO_5/Bi_2TeO_6 system. The oxidation of Bi_2TeO_5 starts at about 450 deg C but completed oxidation can only be achieved in oxygen ambient with a 670 deg C isothermal treatment. The decomposition of Bi_2TeO_6 stars at 663 deg C. Above 790 deg C the loss of TeO_2 is evident. The oxidation rate of Bi_2TeO_5 single crystals is extremly low and develops a very complicated reaction interface changing in the course of reaction.