OPTIMIZATION OF Sr-HEXAFERRITE DYNAMIC GASEOUS HEAT TREATMENT BY CARBON MONOXIDE

Abstract

In this research the influence of dynamic carbon monoxide heat treatment on Sr -hexaferrite has been investigated. Sr -hexaferrite is a hard magnetic material which under gaseous heat treatment, its phase composition and particles size and morphology change significantly. Due to these changings, the magnetic nature of the material changes from hard to soft. Strontium hexaferrite was prepared by conventional route with calcination of Sr -carbonat and hematite at 1100°C for 1 hour. Then Sr -hexaferrite was isothermally heat treated in carbon monoxide dynamic atmosphere at various temperatures and gas flows for different times. The rate of heating and cooling were 10°C/min. The optimum conditions was obtained at 850°C and 20cc/min flow for 0.5 hour. The effect of gaseous heat treatment on phase composition and particles size and morphology characterized by XRD and SEM. The results show the decomposition of Sr -hexaferrite and reduction of the resultant hematite mainly to iron. The crystallite size of the resultant powder was also measured below 50nm.