Relation Between Coarsening and Densification in Solid-state Sintering of Ceramics: Experimental Test on Superfine Zirco
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Relation between coarsening and densification in solid-state sintering of ceramics: Experimental test on superfine zirconia powder compacts J. L. Shi State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Ding-Xi Road, Shanghai, 200050, China (Received 18 September 1997; accepted 6 August 1998)
Coarsening (including grain growth and pore growth) and densification behavior of superfine Y-TZP and YSZ powder compacts in the intermediate stage were investigated. It has been found that grain growth in the compacts is basically not affected by the compaction properties, and pore growth is driven by both grain growth and densification. Grain growth alone leads to size-proportional pore growth, and densification results in pore shrinkage. The relation between grain size and density is analyzed to be linear when grain growth and densification are believed to be driven by different stresses under an identical diffusion process. Both theoretical and experimental results show that compaction properties and the heating rate do not alter this linear relation between grain size and density but influence the slope of the linear relation. Larger dihedral angle, higher green density, and narrower particle and pore size distributions are found favorable for the achievement of the grain size-density trajectory with promoted densification and minimized grain growth. I. INTRODUCTION
For advanced ceramic materials, the investigations of the sintering phenomena are mainly concentrated on densification and microstructure development of the materials. Although densification process is one of the main phenomena in sintering process, however, coarsening process, involving grain growth, pore growth, and diminution, is also an important process in sintering, and more importantly, the coarsening process will affect the densification. Therefore, in order to understand the sintering process well, the relationship between the densification and the growth of pore and grain should be understood first. Microstructure of ceramics is one of the most important factors on which the properties of ceramics depend. Density, grain size, pore size, and defects are some of the most important parameters to affect properties of ceramics, e.g., mechanical properties. The control of the mechanical properties relies on the control of the microstructure development in sintering. To control the microstructure development, the understanding of the relation between densification and grain and pore growth is clearly necessary. In another paper by this author,1 model analysis has been given for the correlation between grain growth and densification for the linear arrays of particles, and the results were compared with the literature.2 This paper gives the test results of the relationships among grain and pore growths and densification of Y-TZP and YSZ powder compacts in pressureless solid-state sintering. II. EXPERIMENTAL PROCEDURE
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