JPS644003A - Manufacture of high-density ferrite - Google Patents

Abstract

PURPOSE:To obtain a high-density ferrite whose particle diameter is large and which contains few voids by a method wherein, after a ferrite material has been sintered at a specific temperature T1, a ferrite sintered material is treated by using a hot hydrostatic press at a temperature T2 lower than the temperature T1 ans at a temperature T3 higher than the temperature T2. CONSTITUTION:After a ferrite material has been sintered at a first temperature T1 of 1100 deg.C<=T1<=1350 deg.C, a ferrite sintered substance is obtained. The ferrite sintered substance is treated by using a hot hydrostatic press at a second temperature T2 which is lower than the first temperature T1, i.e. T1-100 deg.C<=T2<=T1-50 deg.C; the ferrite sintered substance is made dense. Then, the dense ferrite sintered substance is treated by using the hot hydrostatic press at a third temperature T3 which is higher than the second temperature T2; crystal particles are grown. During a process at the temperature T1, the growth of the crystal particles is suppressed to be smaller than 16-17mum; voids remain only at boundaries of the crystal particles; the ferrite sintered substance with a density of more than 90% is obtained. During a process at the temperature T2, the growth of the crystal particles is suppressed; the voids at the boundaries of the crystal particles are crushed; the density is increased to more than 99%; during a process at the third temperature T3, the growth of the particles proceeds while a dense state is kept.