Chemical diffusivity of BaTiO sub(3- delta ) I. Experimental determination

• Published in: Solid state ionics 1999-01, Vol.120 (1), p.141-153
• Main Authors: Song, Chang-Rock, Yoo, Han-Ill
• Format: Article
• Language: English
• ISSN: 0167-2738

The chemical diffusivity of 'undoped' polycrystalline BaTiO sub(3- delta ) was determined via a conductivity relaxation technique, at elevated temperatures (800 less than or equal to T/ degree C less than or equal to 1100) as a function of the ambient oxygen partial pressure in the range of 10 super(-16) less than or equal to P sub(O(2))/atm less than or equal to 1 including an n- to p-type transition regime. Mathematical formulation was developed to convert conductivity relaxation to the corresponding nonstoichiometry ( delta ) relaxation in the transition regime. It has been found that the chemical diffusivity appears to exhibit a maximum at the n-to-p transition point where the electronic minimum conductivity falls, and that surface reaction becomes more rate-determining than diffusion as the transition point is approached from both n-type and p-type branches. Experimental details are given and the results are exhaustively compared with those reported up to date on the 'undoped' BaTiO sub(3).