Metastability of the K2NiF4 type structure of the solid solution LaCa(CrxAl1−x)O4(0⩽x⩽0.10)
- 73 Downloads
Metastability of the K2NiF4 type aluminate LaCaAlO4 and its chromium diluted solid solution LaCaCrxAl1−xO4 (x⩽0.10) was evidenced at 1400‡C in air, in terms of demixing into the parent structures of the 1∶1 intergrowth, i.e. the perovskite and rocksalt type LaAlO3 (LaCrxAl1−xO3) and CaO, respectively. This behaviour is discussed comparatively with YCaAlCO4 and LaSrAlO4 whose structures are stable under the same thermodynamic conditions. The results of a structure analysis are used to emphasize the role of the nine-fold co-ordination of the (A3+=Y3+, La3+; A2+=Ca2+, Sr2+) cations as “mixing” the twelve-fold co-ordination of A3+ in A3+AlO3 perovskite and the six-fold one of A2+ in A2+O rocksalt. Calcium-oxygen underbonding in the (La, Ca)-O-Al bridge is assumed to trigger the metastability of the intergrowth structure at high temperature.
KeywordsPolymer Aluminate Chromium Solid Solution Structure Analysis
Unable to display preview. Download preview PDF.
- 3.Y. P. Oudalov, A. Daoudi, J. C. Joubert, G. Le Flemm and P. Hagenmuller, Bull. Soc. Chem. Fr. 10 (1970) 3408.Google Scholar
- 5.C. C. Pham, J. Choisnet and B. Raveau, Bull. Acad. R. Belg. Cl. Sci. 61 (1975) 473.Google Scholar
- 6.J. Choisnet, F. Archaimbault, M. Crespin, N. Chezina and I. Zvevera, Eur. J. Solid State Inorg. Chem. 30 (1993) 619.Google Scholar
- 7.J. CHOISNET and I. ZVEREVA, unpublished data.Google Scholar
- 8.A. F. WELLS, “Structural Inorganic Chemistry” (Oxford University Press, 1984) p. 586.Google Scholar
- 10.S. Geller and V. B. Bala, Acta Cryst. 9 (1019) 1956.Google Scholar
- 11.W. Hückel, “Structural Chemistry of Inorganic Compounds” (Elsevier, Amsterdam, 1951) p. 123.Google Scholar
- 16.D. CORRIGNAN, Diploma, University of Orléans (1986).Google Scholar