Effects of oxygen deficiency on the acoustic anomalies and phase transition behaviors of barium titanate single crystals
| Autor: | Jae-Hyeon Ko, Namjung Hur, Moongyu Jang, Seonhyeop Shin, Choong Jae Won |
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| Rok vydání: | 2018 |
| Předmět: |
Phase transition
Materials science Brillouin Spectroscopy Condensed matter physics General Physics and Astronomy Mineralogy 02 engineering and technology Dielectric Atmospheric temperature range 021001 nanoscience & nanotechnology 01 natural sciences Condensed Matter::Materials Science chemistry.chemical_compound chemistry Brillouin scattering Phase (matter) 0103 physical sciences Barium titanate Curie temperature General Materials Science 010306 general physics 0210 nano-technology |
| Zdroj: | Current Applied Physics. 18:44-49 |
| ISSN: | 1567-1739 |
| Popis: | The acoustic behaviors of oxygen-reduced barium titanate (BaTiO3-δ) single crystals with δ∼0.04 were investigated as a function of temperature by using Brillouin spectroscopy. The longitudinal acoustic mode of the moderately-reduced BaTiO3 (BTO) showed two pronounced anomalies at approximately 112 °C and −11 °C, which correspond to the cubic-tetragonal and tetragonal-orthorhombic phase transition temperature, respectively. These temperatures were lower by more than 10 °C compared to those of the pure BaTiO3 suggesting that the disorder introduced by oxygen vacancies lowers the phase transition temperatures. The paraelectric phase of the reduced BaTiO3 were characterized by substantial softening of the longitudinal acoustic mode and the growth of central peaks centered at zero frequency. These anomalies were observed in a certain temperature range above the Curie temperature, indicating that pretransitional precursor polar clusters exist in the cubic phase and that their dynamics are responsible for the acoustic anomalies caused by electrostrictive coupling between the strain and the polarization. The relaxation time of the precursor polar clusters derived from the central peak exhibited a critical slowing-down behavior showing that their dynamics becomes more sluggish as temperature approaches the Curie point. |
| Databáze: | OpenAIRE |
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