The Interaction of Zirconia with Oxygen and Its Defect Structure

Abstract

The mass action law is used to describe the reversible exchange between the crystal lattice of ZrO 2 and the ambient medium, and the special features of positioning of interstitial particles in the lattice are taken into account. The ways of equilibrium interaction between the ZrO 2-x lattice with the ambient medium (types of defects that arise) at different partial pressures of oxygen p(O 2 ) and temperatures T are determined, along with the form of the correlation x = f [p(O 2 )], the variation of its composition, the number of charge carriers, mass, volume, and density. The obtained results are compared with the available experimental data. It is demonstrated that, at low temperatures, the lattice defects in pure ZrO 2 are as follows: at high values of p(O 2 ) -oxygen vacancies in the anion sublattice and singly charged anions of oxygen in the interstice, and at low values of p(O 2 ) -vacancies in the anion sublattice and electrons localized on the adjacent cations. At high temperatures, the lattice defects are as follows: at high values of p(O 2 ) -singly charged anions of oxygen and quadruply charged cations of zirconium at the interstice, and at low values of p(O 2 ) -only neutral zirconium atoms at the interstice.

About melting temperature of crystalline materials

“…The types of point defects are determined as are the electrically neutral complexes formed by them, arising in oxides as a result of their interaction with ambient oxygen; and a system of equations describing the dependence of the number of defects on temperature and р(О 2 ) is obtained [1]. Then, the values of the equi librium constants of all reactions of the crystal with oxygen from the environment as a function of temper ature are found for uranium dioxide on the basis of experimental data on the dependence of х = f(р(О 2 )) at Т = const using the weight change of the crystal, that is, its stoichiometry [2].…”