INVESTIGATION OF THE SURFACE OPTICAL PROPERTIES OF OXIDES AS A FUNCTION OF COMPOSITION

摘要

Two main areas of investigation were undertaken:(a) measurements of thermodynamic properties of some nonstoichiometric metal oxides and their mixtures with the aid of a high-temperature galvanic cell technique employing a solid electrolyte;(b) measurements of the thermoelectric power and electrical conductivity of several semiconducting metallic oxides and determination of the effect of doping by ion bombardment on these properties. The thermodynamic phase of the program resulted in an evaluation of the oxygen partial pressure temperature relations in the case of the oxide mixtures studied and oxygen pressure-composition-temperature relations in the case of the nonstoichiometric oxides investigated. These latter data provide a means of distinguishing the predominant point defect present in the nonstoichiometric a-Nb2O5 and Ti02.nThe thermoelectric power and the electrical conductivity of nonstoichiometric Ti02 were studied, both as a function of temperature and oxygen pressure. From this phase of the investigation, it was concluded that Ti02 becomes n-type upon slight reduction, with conduction believed to result from the excitation of electrons from donor centers into a narrow d-conduction band. Doping of single crystals of oxides like MnO and CoO by hydrogen ion bombardment resulted in significant electronic property changes. A model has been proposed to account for the observed changes which postulates that hydrogen is incorporated in the oxide lattice during ionic bombardment.