Raman spectra of Sr3(PO4)2 and Ba3(PO4)2 orthophosphates at various temperatures |
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| Institution: | 1. Key Laboratory of Orogenic Belts and Crustal Evolution, MOE; School of Earth and Space Sciences, Peking University, Beijing 100871, China;2. Institute of Earth Sciences, Academia Sinica, Taipei 115, Taiwan;1. Grupo de Nanomateriais Funcionais (GNF), Departamento de Física, Universidade Federal de Sergipe, 49100-000, São Cristóvão, SE, Brazil;2. Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Cristóvão, SP, Brazil;1. School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, People''s Republic of China;2. State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People''s Republic of China;1. Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan;2. Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan;3. Advanced Research Center for Green Materials Science and Technology, Taipei 10617, Taiwan;1. Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir, Morocco;2. College of Engineering, China Agricultural University, 100083 Beijing, PR China;3. Université de Toulon, Aix Marseille Univ., CNRS 7334, IM2NP, BP 20132, 83957 La Garde Cedex, France;4. Instituto de Ciencia de Materiales de Sevilla, Centro Mixto Universidad de Sevilla-CSIC, Américo Vespucio 49, 41092 Sevilla, Spain |
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| Abstract: | The Raman spectra for Sr3(PO4)2 and Ba3(PO4)2 were investigated in the temperature range from 80 to 1623 K at atmospheric pressure. An unexpected melting of each sample was observed around 1573–1583 K in this study. In the temperature range from 80 to 1323 K, the Raman wavenumbers of all observed bands for Sr3(PO4)2 and Ba3(PO4)2 continuously decrease with increasing temperature. A quantitative analysis on the wavenumbers of Raman bands for both samples reveals that the ν3 antisymmetric stretching vibrations show the strongest temperature dependence and the ν2 symmetric bending vibration displays the weakest temperature dependence. The effects of cations on Raman bands are discussed. The reason for the unexpected melting of both samples is mainly attributed to the significant contribution from excess surface energy and the grain-boundary energy that has apparently lowered the melting points of the small samples, i.e., Gibbs–Thomson effect. |
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| Keywords: | High-temperature Raman spectra |
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