Cation distribution and phase transformations in LiMn2-yTiyO4 (0.2 ≤ y ≤ 1.5) solid solutions

• Published in: Solid state sciences Vol. 7; no. 3; pp. 277 - 286
• Main Authors: PETROV, Kostadin, ROJAS, Rosa M, ALONSO, Pablo J, AMARILLA, José M, LAZARRAGA, Monica G, ROJO, José M
• Format: Journal Article
• Language: English
• Published: Paris Elsevier 01.03.2005
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Electron paramagnetic resonance and relaxation; Exact sciences and technology; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Theory of crystal structure, crystal symmetry; calculations and modeling; Lithium oxides; Powders; Inorganic compounds; Space groups; Phase transformations; Transition element compounds; Cation ordering; Ti-doped LiMn2O4; XRD; Ion distribution; Titanium oxides; Manganese oxides; Solid solutions; Spinels; Ambient temperature; Solid state reaction; Slow cooling; Thermal analysis; Electron paramagnetic resonance; Crystal structure
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2004.10.041

Series of lithium manganese titanium spinel-like oxides LiMn2-yTiyO4 (0.2y1.5) were synthesized by solid state reaction carried out at 1100 deg C, followed by slow cooling to a particular temperature, depending on the titanium content y, and then air-quenched to room temperature. The procedure has permitted to obtain single-phase products. The samples have been characterized by X-ray powder diffraction (XRD), thermal analysis (TG) and electron paramagnetic resonance (EPR) spectroscopy. Compounds whose composition falls within the interval 0.2y1.0 crystallize in the space group Fd3m, whereas those having y > 1.0 crystallize in the space group P4332. Analysis of the structural parameters refined from XRD data revealed that the tetrahedral sites are occupied by Li+ and Mn2+. The end member , which was synthesized in argon atmosphere, is reported for the first time. It crystallizes in the space group P4332, , with all Mn2+ ions being situated at the tetrahedral sites. Its EPR spectrum consists of a Lorentzian-shaped line, centered at g=2.004 with a peak-to-peak width of 25.7 mT. This line has been assigned to Mn2+ ions. Rietveld structure refinement results show that asyincreases from 0 to 1.5 the occupancy factor of Mn2+ in the tetrahedral sites increases from 0 to 0.5, while the occupancy factors of Mn3+ and Mn4+ in the mixed (Mn3+, Mn4+, Ti4+) octahedral sites decrease from 1 to 0.