High pressure effects on the Jahn-Teller distortion in perovskite La0.5-xBixCa0.5MnO3

X-Ray diffraction studies were carried out on the distorted perovskite La0. 5-xBixCa0.5MnO3 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25) under high pressure at ro om temperature by the energy-dispersive technique. The unusual expansion of the 202-040 d-spacing under pressure was observed and accompanied by a rem arkable decrease of the Jahn-Teller distortion in MnO6 octahedra. The chang e of the Mn-O bond angle brings about the disappearance of the basal-plane distortion mode Q(2). The substitution of Bi3- for La3- in the system intro duces more distortions, which is ascribed to the unique lone pair character istics of bismuth. (C) 2001 Elsevier Science B.V. All rights reserved.