High-pressure structural behavior of GdAlO{sub 3} and GdFeO{sub 3} perovskites

• Published in: Journal of solid state chemistry Vol. 177; no. 10
• Main Authors: Ross, N.L., Zhao, J., Angel, R.J.
• Format: Journal Article
• Language: English
• Published: United States 01-10-2004
• Subjects: ALUMINIUM COMPOUNDS; BOND LENGTHS; COMPRESSIBILITY; CRYSTAL STRUCTURE; GADOLINIUM COMPOUNDS; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; IRON COMPOUNDS; MONOCRYSTALS; OXIDES; PEROVSKITE; TEMPERATURE RANGE 0400-1000 K; X-RAY DIFFRACTION
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2004.07.002

The orthorhombic perovskites, GdAlO{sub 3} and GdFeO{sub 3}, have been studied using single-crystal X-ray diffraction up to 8.52 and 8.13GPa, respectively, in a diamond anvil cell at 298K. The evolution of the structures of GdAlO{sub 3} and GdFeO{sub 3} involves compression of both the GdO{sub 12} and the octahedral (AlO{sub 6} and FeO{sub 6}) sites. The compression of the GdO{sub 12} site is anisotropic in both perovskites, with the four longest Gd-O distances compressing more than the eight shorter Gd-O bond lengths, resulting in a decrease in the distortion of GdO{sub 12} with pressure. In GdAlO{sub 3}, the GdO{sub 12} site is less compressible than the AlO{sub 6} site, resulting in an increase of both the interoctahedral Al-O1-Al and Al-O2-Al angles with increasing pressure. Thus GdAlO{sub 3} perovskite becomes less distorted with increasing pressure. In GdFeO{sub 3}, the GdO{sub 12} site displays a similar compressibility as the FeO{sub 6} site, with little change in the Fe-O2-Fe angle with pressure but an increase of the Fe-O1-Fe tilting angle. Thus GdFeO{sub 3} perovskite becomes less distorted with increasing pressure, but the change is not as pronounced as GdAlO{sub 3}. The high-pressure behavior of GdAlO{sub 3} and GdFeO{sub 3} is similar to orthorhombic YAlO{sub 3} perovskite but contrasts with orthorhombic CaSnO{sub 3}, which becomes more distorted with increasing pressure.