ABSTRACT
High-purity undoped and 500 ppma Ti-doped alumina compacts were prepared and sintered at temperatures from 1350°C to 1550°C in vacuum. Hot isostatic pressing was used to fully densify the compacts. The growth of matrix grains in these dense compacts during anneals in vacuum and in air, and the growth of single crystal seeds into the dense alumina were investigated. Microstructural evolution was observed by SEM. Ti doping increases the sintering rate during early stages of sintering, but does not allow sintering to full density. Ti-doped compacts develop faceted microstructures, with the faceting most pronounced in the sample center, where Ti4+ is the dominant impurity. During grain growth, faceted microstructures become more pronounced. Preliminary seed growth results suggest that the mobility of ( 1 1 2 ¯ 0 ) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003067566/46ee6d67-a566-45e6-bef6-adce045e90e6/content/inline-math52.tif"/> seeds growing into Ti-doped material is >3x that previously reported for growth into nominally undoped alumina.
