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Title: Investigation of polymorphism and vibrational properties of MnMoO4 microcrystals prepared by a hydrothermal process.
Authors: Martins, Guilherme Mendes
Coelho, Pâmela de Oliveira
Siqueira, Kisla Prislen Félix
Moreira, Roberto Luiz
Dias, Anderson
Issue Date: 2018
Citation: MARTINS, G. M. et al. Investigation of polymorphism and vibrational properties of MnMoO4 microcrystals prepared by a hydrothermal process. Crystal Growth & Design, v. 18, n. 4, p. 2474-2485, 2018. Disponível em: <>. Acesso em: 7 mar. 2019.
Abstract: MnMoO4 microcrystals were synthesized by hydrothermal methods, and their structural, morphological, and vibrational properties were investigated. Conventional reactors and microwave-heated hydrothermal vessels were used to synthesize micrometer-sized MnMoO4 polymorphs at different temperature and time conditions. MnMoO4·H2O crystals were obtained in both reactors at temperatures below 200 °C, for times up to 24 h. These microcrystals belong to the triclinic P1̅ space group, and their 26 characteristic Raman bands were identified. A monoclinic MnMoO4 polymorph belonging to the P2/c structure was synthesized at temperatures higher than 200 °C only into conventional hydrothermal reactors. Polarized micro-Raman analyses have evidenced and allowed the assignment of 18 phonon modes predicted by group-theory calculations for this polymorph. Another MnMoO4 polymorph, within the monoclinic C2/m space group, was obtained by two processing routes: (i) heating the P2/c microcrystals at 600 °C; or (ii) heating the MnMoO4·H2O phase at 250 °C. For this monoclinic phase, 33 Raman-active bands were identified and assigned, in very good agreement with group-theoretical calculations, which predict 36 modes for the C2/m polymorph. Well-faceted, highly crystalline microcrystals were clearly observed by scanning and transmission electron microscopies, in perfect agreement with X-ray diffraction and Raman spectroscopic analysis. Finally, the appearance of characteristic phonon modes related to molybdenum in octahedral coordination suggests an incipient crystallization of a new, unreported α-MnMoO4 polymorph, at least in a short-range degree.
ISSN: 1528-7505
Appears in Collections:DEQUI - Artigos publicados em periódicos

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