Oxidation of Bismuth Tellurite, Bi2TeO5: I. Thermoanalytical and Optical Microscopic Studies

Deatailed thermoanalytical experiments were carried out to reveal the oxidative and reductive processes in the Bi2TeO5/Bi2TeO6 system. The oxidation of Bi2TeO5 starts at about 450°C but completed oxidation can only be achieved in oxygen ambient with a 670°C isothermal treatment. The decomposition of Bi2TeO6 stars at 663°C. Above 790°C the loss of TeO2 is evident. The oxidation rate of Bi2TeO5 single crystals is extremly low and develops a very complicated reaction interface changing in the course of reaction.