Internal friction investigation of phase transformation in nearly stoichiometric LaMnO3+δ

• Published in: Journal of the European Ceramic Society 2005-03, Vol.25 (6), p.935-941
• Main Authors: ZENATI, R, BERNARD, C, CALMET, C, GUILLEMET, S, FANTOZZI, G, DURAND, B
• Format: Article
• Language: English
• Subjects: Anelasticity, internal friction, stress relaxation, and mechanical resonances; Chemical Sciences; Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Material chemistry; Mechanical and acoustical properties of condensed matter; Physics; Structure of solids and liquids; crystallography
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2004.03.015

Rhombohedral LaMnO3+delta powders, prepared by two different soft chemistry routes (co-precipitation and hydrothermal synthesis), are sintered at 1400 C for 2 h in air. Measurements of internal friction Q(-1)(T) and shear modulus G(T), at low frequencies from -180 to 700 C under vacuum, evidence three structural transitions of nearly stoichiometric orthorhombic LaMnO3+delta. The first one, at 250 or 290 C, depending on the processing followed, is associated to either a Jahn-Teller structural transition or a phase transformation from orthorhombic to pseudo-cubic. The second one at 610 or 630 C is related to a phase transformation from pseudo-cubic or orthorhombic to rhombohedral. Below the Neel temperature, around -170 C, a relaxation peak could be associated, for samples prepared according to both processing routes, to the motion of Weiss domains.