A High-Pressure Raman Study of Mixed Perovskites BaCexZr1−xO3 (0≤x≤1)

✍ Scribed by C. Chemarin; N. Rosman; T. Pagnier; G. Lucazeau

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 302 KB
• Volume: 149
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8530

✦ Synopsis

A high-pressure Raman study of polycrystalline samples of BaCe x Zr 1؊x O 3 is performed at room temperature. The evolution of Raman spectra with pressure is compared to the evolution of the Raman spectra of BaZrO 3 and BaCeO 3 . The e4ect of composition on the pressure-induced phase transitions is monitored from the Raman spectra. Transitions toward lower symmetry phases as pressure increases are evidenced. A phase diagram in the binary system BaZrO 3 +BaCeO 3 based on the Raman spectra characteristic of the di4erent structures of BaCeO 3 (Pnma, Imma, R3 c, Pm3m) is proposed. The transition pressures toward low-symmetry structures decrease when Ce is replaced for Zr. This study allows us to interpret the BaCe x Zr 1؊x O 3 (04x41) Raman spectra at ambient pressure on the basis of nanodomains and nanophases. These objects tend to disappear upon pressure increase. The octahedra to dodecahedra volumes ratio is used as a critical parameter that is able to reproduce qualitatively some of the phase transitions in the mixed perovskites BaCe x Zr 1؊x O 3 . In order to calculate this parameter vs pressure, a derivation of the samples: compressibility based on a polyhedral approach is performed and is found in the range [0.7؋10 ؊11 +1.0؋ 10 ؊11 Pa ؊1 ].