Reaction front occurrence on imperfection profiles during oxygen chemical diffusion in oxides. I. Thermodynamic background

TL;DR

This paper provides a thermodynamic analysis of how oxygen diffusion affects metal dopant states and conduction types in oxides, emphasizing the importance of reaction constants and equilibrium conditions.

Contribution

It introduces a theoretical framework for understanding oxygen diffusion effects on dopant ionization and conduction in oxides, highlighting the role of reaction constants and non-simultaneous transitions.

Findings

Critical transitions depend on different reaction constants.

Oxygen vacancy acts as a shallow donor.

Experimental data can help determine reaction constants.

Abstract

We present a theoretical study of the impact of oxygen diffusion in oxide crystals on metal dopants ionic state and the conduction type under thermal equilibrium. Oxygen vacancy formation acting as a shallow, double-electronic donor is assumed to result from the crystal exposure to a low ambient oxygen pressure. It is shown, that critical transitions from n- to a p-type at an oxygen partial pressure Pi, and in ionization state of the metal dopant at an oxygen partial pressure PM, are usually not simultaneous, and depend on the different reaction constants. Experimental study of the different species concentrations at thermodynamic equilibrium as functions of pressure and temperature should allow assessment of various reversible reaction constants controlling the process. In the Part II companion paper, the kinetic (diffusion) characteristics are considered in detail.