The Conversion Polymorphism of Perovskite Phases in the BiCrO<sub>3</sub>–BiFeO<sub>3</sub> System
Perovskite-type materials containing Bi<sup>3+</sup> cations at A sites are interesting from the viewpoints of applications and fundamental science as the lone pair of Bi<sup>3+</sup> cations often stabilizes polar, ferroelectric structures. This can be illustrated by a lot o...
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| Format: | Article |
| Language: | English |
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MDPI AG
2025-03-01
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| Series: | Inorganics |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2304-6740/13/3/91 |
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| Summary: | Perovskite-type materials containing Bi<sup>3+</sup> cations at A sites are interesting from the viewpoints of applications and fundamental science as the lone pair of Bi<sup>3+</sup> cations often stabilizes polar, ferroelectric structures. This can be illustrated by a lot of discoveries of different new functionalities in bulk and thin films of BiFeO<sub>3</sub> and its derivatives. In this work, we investigated solid solutions of BiCr<sub>1−<i>x</i></sub>Fe<i><sub>x</sub></i>O<sub>3</sub> with 0.1 ≤ <i>x</i> ≤ 0.4 prepared by a high-pressure (HP) method and post-synthesis annealing at ambient pressure (AP). HP-BiCr<sub>1−<i>x</i></sub>Fe<i><sub>x</sub></i>O<sub>3</sub> modifications with 0.1 ≤ <i>x</i> ≤ 0.3 were mixtures of two phases with space groups <i>C</i>2/<i>c</i> and <i>Pbam</i>, and the amount of the <i>C</i>2/<i>c</i> phase decreased with increasing <i>x</i>. The amount of the <i>C</i>2/<i>c</i> phase was also significantly decreased in AP-BiCr<sub>1−<i>x</i></sub>Fe<i><sub>x</sub></i>O<sub>3</sub> modifications, and the <i>C</i>2/<i>c</i> phase almost disappeared in AP-BiCr<sub>1−<i>x</i></sub>Fe<i><sub>x</sub></i>O<sub>3</sub> with 0.2 ≤ <i>x</i> ≤ 0.3. Fundamental, strong reflections of HP-BiCr<sub>1−<i>x</i></sub>Fe<i><sub>x</sub></i>O<sub>3</sub> and AP-BiCr<sub>1−<i>x</i></sub>Fe<i><sub>x</sub></i>O<sub>3</sub> were almost unchanged; on the other hand, weak superstructure reflections were different and showed clear signs of strong anisotropic broadening and incommensurate positions. These structural features prevented us from determining their room-temperature structures. On the other hand, HP-BiCr<sub>1−<i>x</i></sub>Fe<i><sub>x</sub></i>O<sub>3</sub> and AP-BiCr<sub>1−<i>x</i></sub>Fe<i><sub>x</sub></i>O<sub>3</sub> showed high-temperature structural phase transitions to the GdFeO<sub>3</sub>-type <i>Pnma</i> modification at <i>T</i><sub>srt</sub> = 450 K (<i>x</i> = 0.1), <i>T</i><sub>srt</sub> = 480 K (<i>x</i> = 0.2), <i>T</i><sub>srt</sub> = 510 K (<i>x</i> = 0.3), and <i>T</i><sub>srt</sub> = 546 K (<i>x</i> = 0.4). Crystal structures of the GdFeO<sub>3</sub>-type <i>Pnma</i> modifications of all the samples were investigated by synchrotron powder X-ray diffraction. Magnetic properties of HP-BiCr<sub>1−<i>x</i></sub>Fe<i><sub>x</sub></i>O<sub>3</sub> and AP-BiCr<sub>1−<i>x</i></sub>Fe<i><sub>x</sub></i>O<sub>3</sub> were quite close to each other (HP vs. AP), and the <i>x</i> = 0.2 samples demonstrated negative magnetization phenomena without signs of the exchange bias effect. |
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| ISSN: | 2304-6740 |