Phase relation of Na{sub 1-x}K{sub x}MgF{sub 3} (0 {<=} x {<=} 1) perovskite-type solid-solutions
Na{sub 1-x}K{sub x}MgF{sub 3} (0{<=}x{<=}1) solid-solutions were synthesized and the phase diagram of NaMgF{sub 3}-KMgF{sub 3} system was determined by high temperature X-ray powder diffraction experiments and differential thermal analysis (DTA). This system is characterized by a complete series of solid solutions, with a minimum in the solidus at 30 mol% KMgF{sub 3} and 1279 K. No immiscibility gap was found. The crystal system changes from orthorhombic to cubic at x=0.22 at room temperature. The volume change of the unit cell as a function of composition shows a large deviation (excess volume) from Vegard's law for solid solution. The transition temperatures of NaMgF{sub 3} and Na{sub 0.9}K{sub 0.1}MgF{sub 3} from orthorhombic to cubic are 1043 and 723 K, respectively. The transition temperature decreases rapidly by the effect of replacing Na by K. Axial ratios of b/a and c/{radical}2a in orthorhombic NaMgF{sub 3} and Na{sub 0.9}K{sub 0.1}MgF{sub 3} decrease linearly with temperature toward the transition and then discontinuously changes to cubic at the transition point.
- OSTI ID:
- 20884648
- Journal Information:
- Materials Research Bulletin, Vol. 38, Issue 3; Other Information: DOI: 10.1016/S0025-5408(02)01059-0; PII: S0025540802010590; Copyright (c) 2003 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
- Country of Publication:
- United States
- Language:
- English
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