SOLID-STATE SINTERING OF HYDROTHERMAL POWDERS - DENSIFICATION AND GRAIN-GROWTH KINETICS OF NICKEL-ZINC FERRITES

The hydrothermal process was employed to produce single-phase submicro metric NiZn ferrites. The materials were sintered in air at different temperatures and times (1100 to 1400 degrees C, 5 to 240 min). After s intering, highly dense ceramic bodies with different microstructures w ere obtained. X-ray diffraction, helium pycnometry, nitrogen adsorptio n technique, and optical and scanning electron microscopy were used to determine the microstructural parameters of the samples. The modeling of the sintering process demonstrates a crossover between the densifi cation mechanisms from grain boundary diffusion to lattice diffusion w ith increasing sintering temperature. It is also shown that, in the fi nal-stage sintering, the grain growth kinetics is controlled by pore d rag. (C) 1998 Elsevier Science Ltd.