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January 28th, 2010

The Emergence of Intergranular Precipitates in TiO2-Doped alpha-Al2O3 Ceramics

Published on January 28th, 2010 | By: pwray@ceramics.org

Volume 93 Issue 2, Pages 326 – 329

 

Pengxiang Qian, Hui Gu, Miaofang Chi
Published Online: Nov 23 2009 6:57PM
DOI: 10.1111/j.1551-2916.2009.03410.x

 

ABSTRACT
The minor phase accumulated at intergranular regions in ceramics is usually associated with the global doping level of additives; however, such simplification often undermines the local variation in liquid composition that leads to the emergence of precipitation. In this paper the correlation between precipitation and intergranular liquid was investigated in a TiO2-doped Al2O3 ceramic system. The discrepancy between XRD and SEM in detection of the intergranular Al2TiO5 phase was rationalized by their difference in sensitivity that corresponds to a change from the casual to general mode of local liquid variation. Analytical TEM in addition revealed Ti-rich nanoprecipitates aligning along grain boundary (GB). The two intergranular phases were associated with separate processes of intergranular liquid, as clarified via a representative case that exhibited the extra grain growth from annealing. The nanoprecipitates were created from a binary liquid in local equilibration with segregation to GB, which served as transporting routes to form ternary liquid at the multigrain junctions to initiate the main intergranular phase Al2TiO5.

 

Online Access to Journal of the American Ceramic Society


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