DIFFUSION PROCESSES AND STRUCTURIZATION IN MICROWAVE SINTERING OF BaTiO_3-SrTiO_3 AND Al_2O_3-Cr_2O_3 POWDER SYSTEMS WITH COMPLETE MISCIBILITY

摘要

The paper examines the compaction and structurization of equimolar BaTiO_3-SrTiO_3 and Al_2O_3-Cr_2O_3 powder mixtures with complete miscibility and monophase Al_2O_3 and Cr_2O_3 powders under microwave heating (24 and 30 GHz) (MWH) and conventional heating (CH). A gyrotron system is used for MWH and electric furnaces for CH. The samples are prepared by sintering of ultrafine powder mixtures at 1000-1300 deg C (MWH) and 1700 deg C (CH). Mercury porometry is used to determine the mean pore size and specific surface area of the samples. The Barus-Bechgold method is employed to find the maximum pore contraction. A quantitative microscopic analysis of the samples is carried out. The content of solid solution is determined using x-ray analysis. The volume and local shrinkage is calculated. Relationships between the local and volume shrinkage, pore structure parameters, and amounts of solid solutions for different heating conditions are shown. The results reveal different diffusion processes in sintering of powder systems with complete miscibility of components under MWH and CH.