| 摘要 |
PURPOSE:To obtain a spherical electrophotographic ferrite carrier having long life and high electric resistance and forming an image superior in sharpness etc. by heat-treating a ferrite contg. Fe2O3 as an essential component and NiO and MnO in a specified molar ratio. CONSTITUTION:Starting materials are weighed and mixed to obtain a ferrite composed of 5-30mol% NiO, 5-30mol% MnO, and 40-70mol% Fe2O3, or a ferrite having a part of this compsn. substd. by a monovalent or higher valent metal, such as ZnO. This powder mixture is calcined, pulverized, granulated, burned at 1,100-1,400 deg.C, and finally heat-treated at about 700 deg.C for about 2hr in a nitrogen atm. to obtain the intended electrophotographic ferrite carrier. The obtained ferrite carrier has 10<2>-10<13>OMEGA-cm resistivity, >=10emu/g saturation magnetization, >=10mu magnetic permeability, >=100 deg.C Curie. temp., and >=1,000g/ cm<2> particle strength. |
