ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 17, Number 5
JKCSEZ 17(5)
October 20, 1973 

The nonstoichiometry of the iron oxide system has been studied by analyzing the weight loss of a sample, measured by using a quartz microbalance, in a temperature range from 0℃ to 1200℃ under oxygen pressures from 102 mmHg to 10-4 mmHg. The Y values of the formula, FeO1+Y, that have been obtained by this means for various conditions of temperature and pressure in this range are considered to be more accurate than values obtained by methods requiring thste quenching of the sample before measurements are made. The plots of log Y vs log PO2 (or log Y = n log PO2) show linearity and n calculated from the slope of the plot is about 1/10 at 1000℃, indicating a difference between the nonstoichiometric and oxidation mechanisms. The condition for the formation of stoichiometric FeO was determined to be 1200℃ under 10-3 mmHg of O2 and the composition of the oxide under standard conditions was FeO1.11185. As in general more oxygen dissolves into the oxide system at lower temperatures and higher oxygen pressures, the deviation from stoichiometric FeO is greater under those conditions. A comparison of the change in conductivity of the sample indicates that full phase transition does not take place with conductivity transition.