Effect of Preparation Conditions on Phase Formation, Densification, and Microstructure Evolution in La‐β‐Al 2 O 3 /Al 2 O 3 Composites

In situ development of La‐ß‐Al 2 O 3 (LBA) platelets in alpha‐Al 2 O 3 was studied as a function of the preparation method: a conventional solid‐state reaction of commercial Al 2 O 3 powder and La(NO 3 ) 3 as well as a sol‐gel method starting with boehmite and the same La 2 O 3 precursor. In both cases, homogeneous distribution of the reinforcing phase was achieved, and a noteworthy inhibition of Al 2 O 3 grain growth resulted. However, samples prepared by solid‐state reaction densified more easily than those prepared via sol‐gel, but the formation of the LBA phase occurred at a lower temperature in samples prepared by the sol‐gel approach. Results on the correlation of the onset of LBA grain growth and densification to microstructure are discussed.