Structural transformation during sintering and annealing of beta alumina

• Published in: Journal of materials science Vol. 19; no. 7; pp. 2223 - 2232
• Main Author: HEAVENS, S. N
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01.07.1984
• Subjects: annealing; beta alumina; ceramics; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; heat treatment; Inorganic compounds; lattices; phase transitions; Physics; powder metallurgy; sintering; structural analysis; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Water, oxides, hydroxides, peroxides; X-ray diffraction; Aluminium Oxides; Optical microscopy; Heat treatment; Beta form; Sintering; Chemical composition; Experimental study; Microstructure; Lattice parameters; X ray diffraction; Oxide ceramics; Inorganic compound
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/BF01058099

Changes in the phase content, microstructure and lattice parameter are observed in stabilized beta/beta double prime alumina specimens following extended sintering and annealing treatments. The resulting state is dependent on composition of the starting powder and on temperature and duration of heat treatment; the kinetics of transformation between beta and beta double prime alumina are generally slow and certain beta/beta double prime ceramics remain in a metastable state even after a prolonged high temperature anneal. Following post-sinter heat treatment, splitting of X-ray diffraction peaks reveals a segregation of the beta double prime phase into two components of differing lattice parameter. With sintering schedules of a long duration the splitting may even be present in the as-fired condition as recently reported by Harbach (1983). The splitting is attributed to a structural change resulting from the expulsion of Na2O from supersaturated beta double prime grains.