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

Abstract

Rhombohedral LaMnO 3+δ 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 LaMnO 3+δ . 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.

Characterization of perovskite-type cathode, La0.75Sr0.25 Mn0.95−xCox Ni0.05O3+δ (0.1≤x≤0.3), for intermediate-temperature solid oxide fuel cells

“…This also indicates a large increase in oxygen vacancies in region I and its invariance in region II [9]. A change in slopes is observed in a temperature region 260-290 • C probably due to the Jahn-Teller structural transition as observed earlier for the nearly stoichiometric LaMnO 3+ı [32]. It is also worth mentioning that the TG increases with increasing x, suggesting an increase in oxygen vacancies.…”

Internal Friction on AISI 304 Stainless Steels with Low Tensile Deformations at Temperatures between−50 and 20C

“…Internal friction measurements can be used to evaluate phenomena which affect the mechanical performance of a material, such as the ageing after deformation, precipitation, changes of Young modulus or shear modulus, and phase transformations [13,14]. Some internal friction applications which involve phase transformations are the study of martensite in alloys with shape memory effect [17] and phase transformations in magnetic oxides [18]. Studies of mechanical relaxation spectroscopy in copper alloys [19] showed that the higher internal friction in martensite phase was caused by movement of twin boundaries and martensites plate boundaries.…”

Ultrafine Grinding of MgTiO3 Based Ceramic Influencing the Material Properties

“…The average diameter was obtained by the slope inverse of the line obtained. The distortion was obtained from the y-intercept [31].…”