Abstract
Typical titanium-based perovskite oxides Eu1-xBaxTiO3 (x = 0.6-0.8), EU1-xKxTiO3 (x = 0.2,0.32), and La0.7(Na, K)0.3TiO3 were synthesized by high pressure and temperature using RE2O3 (RE = -La, Eu), TiO2, alkaline, or alkaline earth carbonates as the starting materials. X-ray diffraction data analysis showed that there was a structural transformation in EU1-xBaxTiO3 by varying Ba content [i.e., from cubic (x = 0.6,0.7) to tetragonal (x = 0.8)], and that samples Eu1-xKxTiO3 and La0.7(Na, K)0.3TiO3 crystallized in the cubic perovskite structure. 151Eu Mössbauer spectroscopy and electron paramagnetic resonance measurements revealed mixed valence of Eu2+/Eu3+ in samples Eu1-xBaxTiO3 and Eu1-xKxTiO3, while Ti ions were present in pure Ti4+ state. Cubic Eu1-xKxTiO3 was metastable, which decomposed into a mixture of perovskite and pyrochlore phases at high temperatures as accompanied by an oxidation process from Eu2+ to Eu3+. For samples La0.7(Na, K)0.3TiO3, Ti3+ signals were clearly observed. The reduction mechanisms for Eu ions at A site and Ti ions at B site in the perovskite oxides are discussed in terms of the chemical nature of the framework ions and substitution ions under high pressure and temperature.
Original language | English |
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Pages (from-to) | 417-424 |
Number of pages | 8 |
Journal | Journal of Materials Research |
Volume | 16 |
Issue number | 2 |
DOIs | |
Publication status | Published - 2001 Feb |
ASJC Scopus subject areas
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering