Microwave Sintering of Si3N4-Ceramics Adding Yttrium or Ytterbium Oxides

• Published in: Key engineering materials 2001, Vol.206-213, p.385-388
• Main Authors: Holoptsev, V.V., Getman, Olga, Plotnikov, I.V., Panichkina, V.V., Skorokhod, Valeriy
• Format: Article
• Language: English
• ISSN: 1013-9826; 1662-9795; 1662-9795
• DOI: 10.4028/www.scientific.net/KEM.206-213.385

The compaction, the alpha - beta-phase transformation processes and the evolution of the porous structure of Si3N4-base ceramics during initial stage sintering under microwave heating (MWH) (30GHz) and traditional heating (TH) were investigated. The materials under investigation were powder blends of silicon nitride with oxides: 3 percent Al2O3 and 5 percent Y2O3 (or Yb2O3). The average particle powder sizes were 0.5-1.0 micron. The compacts were heated to temperatures 1500, 1600, 1700 and 1750 C with the heating rate of 60 deg/min in nitrogen at normal pressure. Some samples were heated at the rates of 30 and 90 deg/C under MWH only. Upon reaching prescribed temperature the samples were cooled without isothermal holds. It has been found that under MWH the compaction and the onset of alpha - beta-phase transformation in the investigated materials occur at temperatures that are more than 100 C lower than those typical under TH. It has been established that under MWH the compaction degree of samples increases and the alpha - beta-phase transformation degree decreases when the heating rate rises from 30 to 90 deg/min. Under MWH the ceramic samples conserve their fine porous structure to high temperatures in comparison with TH. (Author)