Raman scattering study of the high temperature phase transitions of NaTaO3.

• Autor(es): Teixeira, Nayara Gomes ; Dias, Anderson ; Moreira, Roberto Luiz
• Data: 2012
• Origem: Oasisbr
• Assunto(s): Dielectric properties; Capacitors; Sintering; Spectroscopy; Perovskites
• Tipo de Documento: Artigo científico
• Idioma: Inglês

Descrição

The phase transition sequence of sodium tantalate (NaTaO3) ceramic samples has been investigated by Raman spectroscopy, from room temperature up to 640 ◦C. At room temperature, NaTaO3 shows an orthorhombically distorted perovskite structure belonging to the Pbnm space group. Raman and infrared vibrational spectra at 20 ◦C are in relative good agreement with group theory predictions for this group. At high temperatures, NaTaO3 shows three phase transitions, in the sequence Pbnm (∼450 ◦C) Cmcm (∼560 ◦C) P4/mbm (∼620 ◦C) Pm¯3m. The Raman spectra for the two intermediate high temperature phases showed a decreasing of the number of the active modes, accompanied by band broadening, and were well compatible with structural symmetry increasing at higher temperatures.