Oxygen Content of Nickel Ferrites at 1300°C

Abstract

The oxygen contents for compositions with the spinel structure in the system Fe‐Ni‐O were determined at 13OO°C for oxygen pressures from 10 −3.6 to 10°atm. The ferrite region, from an Fe/Ni ratio of 2.035 to magnetite, was investigated. Below Fe/Ni = 2.5 only oxygen‐deficient ferrites exist. Above Fe/Ni = 7.6 only ferrites with an oxygen excess were found and for the intermediate nickel contents, ferrites with both types of oxygen nonstoichiometry were found. Previous phase equilibria studies, which do not report single‐phase ferrite with an oxygen deficiency, are discussed.