PURPOSE: To manufacture γ-Fe2O3 having an increased temp. of transition to α-Fe2O3 by pulverizing and heat treting a powdered mixture contg. a specified percentage each of Fe3O4, γ-Al2O3 and La, Cl, Pr or Nd under specified conditions and by oxidizing the heat treated powder.
CONSTITUTION: A powdered mixture contg. 89.95W25mol% Fe2O3, 10W60mol% γ-Al2O3 and at least one of La, Ce, Pr and Nd by 0.05W15mol% in total as La2O3, Ce2O3, PrO3 and Nd2O3 is pulverized for ≥100min and heat-treated at 600W1,200°C in a nonoxidizing atmosphere for about 1hr. The heat-treated powder is heated to about 400°C in air at about 100°C/hr heating rate and held at about 400°C for about 1hr to obtain γ-Fe2O3 by oxidation. Thus, the temp. of transition of γ-Fe2O3 to α-Fe2O3 can be shifted considerably to the high temp. side.
NAKATANI SEIICHI
NAKATANI YOSHIHIKO
