Characterization of polycrystalline (Na,K)β/β′- alumina ceramics |
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Authors: | Kimihiro Yamashita Patrick S Nicholson |
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Institution: | Ceramic Engineering Research Group, Department of Metallurgy and Materials Science, McMaster University, Hamilton, Ontario, L8S 4L7 Canada |
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Abstract: | K β′-alumina is unstable at >1300°C. Mixed alkali β′-alumina has a variable stability depending on the alkali ratio, K+]/(Na+]+K+]). For f(β)<K+]/(Na+]+K+]), the β′-Al2O3 phase decomposes to Kβ-Al2O3 0997 0815 V 3 and a solid solution of Na β′-Al2O3 and K β′-Al2O3. For f(β)=K+]/(Na+]+K+], the ceramic consists of K β-Al2O3 and Naβ′-Al2O3 and for f(β)>K+]/(Na+]+K+]), the excess Na+ after Na β′-Al2O3 dissolves in the β phase, giving Na β-Al2O3/K β-Al2O3 solid solution and Na β′-Al2O3. These sequences were confirmed by measuring the dependence of the c-axis lattice parameters of β- and β′-Al2O3 phases on the f(β), and the change of these parameters during the ion-exchange of Na+ and K+ ions. |
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