A computer simulation study of the defect structure of calcia-stabilized zirconia

Abstract

The defect structure of calcia-stabilized zirconia, a topic of long-standing controversy, has been examined by atomistic computer simulation techniques. Defect association energies for an anion vacancy and a dopant calcium ion at both nearest-neighbour and next-nearest-neighbour (NNN) positions have been determined and suggest the preferential siting of oxygen vacancies in the NNN position with respect to the dopant cation, at low dopant concentrations. A structural explanation for this is proposed. Our calculations also suggest Schottky intrinsic disorder in cubic zirconia which may be atypical compared with other fluorite-structured oxides; we advance an explanation for this in terms of lattice relaxation. Excellent agreement between experimental and calculated values shows the reliability and potential of computer simulation techniques. Binding energies of various types of defect cluster were calculated to check their relative stabilities. Also the migration energy of the oxygen vacancy was calculated in order to determine the favourable jumps of vacancies in the lattice of zirconia.