Abstract
It was recently found that nanowires of PbTiO 3 synthesized through an intermediate pre-perovskite phase exhibit enhanced spontaneous polarization. Here we investigated the pre-perovskite PbTiO 3 (PP-PTO) nanowire phase at finite temperatures employing first-principles quasiharmonic calculations. We calculated its band gap, phonon dispersions, phonon density of states, Debye temperature, and thermodynamic properties. The corresponding calculations for cubic and tetragonal PbTiO 3 were also carried out for comparison. In the current calculations, the amount of imaginary frequencies associated with the ideal cubic PTO structure, i.e., a cubic cell shape with ion positions at the ideal cubic perovskite lattice sites, was decreased to a negligible level by employing a constrained cubic structure, a structure with the same cubic cell shape as the ideal cubic PTO structure but allowing the ion positions to relax to thermodynamically more stable tetragonal positions at 0 K. In contrast to the general observation that a higher volume phase would have relatively higher entropy, it is found that the PP-PTO phase possesses the lowest entropy while having the largest volume compared to cubic and tetragonal PbTiO 3 phases. Furthermore, the temperature-pressure phase diagram for the three PbTiO 3 phases was obtained, which demonstrates that PP-PTO could be stabilized under a large volume or a negative pressure. This study provides insights to experimentally synthesizing the PP-PTO phase and to better understanding its phase transition into the converted tetragonal PbTiO 3 nanowires with enhanced piezoelectric and ferroelectric properties.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 146-153 |
| Number of pages | 8 |
| Journal | Acta Materialia |
| Volume | 171 |
| DOIs | |
| State | Published - Jun 1 2019 |
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All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Polymers and Plastics
- Metals and Alloys
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First-principles lattice dynamics and thermodynamic properties of pre-perovskite PbTiO 3 . / Zhou, Meng Jun; Wang, Yi; Ji, Yanzhou; Liu, Zi-kui; Chen, Long-qing; Nan, Ce Wen.
In: Acta Materialia, Vol. 171, 01.06.2019, p. 146-153.Research output: Contribution to journal › Article
TY - JOUR
T1 - First-principles lattice dynamics and thermodynamic properties of pre-perovskite PbTiO 3
AU - Zhou, Meng Jun
AU - Wang, Yi
AU - Ji, Yanzhou
AU - Liu, Zi-kui
AU - Chen, Long-qing
AU - Nan, Ce Wen
PY - 2019/6/1
Y1 - 2019/6/1
N2 - It was recently found that nanowires of PbTiO 3 synthesized through an intermediate pre-perovskite phase exhibit enhanced spontaneous polarization. Here we investigated the pre-perovskite PbTiO 3 (PP-PTO) nanowire phase at finite temperatures employing first-principles quasiharmonic calculations. We calculated its band gap, phonon dispersions, phonon density of states, Debye temperature, and thermodynamic properties. The corresponding calculations for cubic and tetragonal PbTiO 3 were also carried out for comparison. In the current calculations, the amount of imaginary frequencies associated with the ideal cubic PTO structure, i.e., a cubic cell shape with ion positions at the ideal cubic perovskite lattice sites, was decreased to a negligible level by employing a constrained cubic structure, a structure with the same cubic cell shape as the ideal cubic PTO structure but allowing the ion positions to relax to thermodynamically more stable tetragonal positions at 0 K. In contrast to the general observation that a higher volume phase would have relatively higher entropy, it is found that the PP-PTO phase possesses the lowest entropy while having the largest volume compared to cubic and tetragonal PbTiO 3 phases. Furthermore, the temperature-pressure phase diagram for the three PbTiO 3 phases was obtained, which demonstrates that PP-PTO could be stabilized under a large volume or a negative pressure. This study provides insights to experimentally synthesizing the PP-PTO phase and to better understanding its phase transition into the converted tetragonal PbTiO 3 nanowires with enhanced piezoelectric and ferroelectric properties.
AB - It was recently found that nanowires of PbTiO 3 synthesized through an intermediate pre-perovskite phase exhibit enhanced spontaneous polarization. Here we investigated the pre-perovskite PbTiO 3 (PP-PTO) nanowire phase at finite temperatures employing first-principles quasiharmonic calculations. We calculated its band gap, phonon dispersions, phonon density of states, Debye temperature, and thermodynamic properties. The corresponding calculations for cubic and tetragonal PbTiO 3 were also carried out for comparison. In the current calculations, the amount of imaginary frequencies associated with the ideal cubic PTO structure, i.e., a cubic cell shape with ion positions at the ideal cubic perovskite lattice sites, was decreased to a negligible level by employing a constrained cubic structure, a structure with the same cubic cell shape as the ideal cubic PTO structure but allowing the ion positions to relax to thermodynamically more stable tetragonal positions at 0 K. In contrast to the general observation that a higher volume phase would have relatively higher entropy, it is found that the PP-PTO phase possesses the lowest entropy while having the largest volume compared to cubic and tetragonal PbTiO 3 phases. Furthermore, the temperature-pressure phase diagram for the three PbTiO 3 phases was obtained, which demonstrates that PP-PTO could be stabilized under a large volume or a negative pressure. This study provides insights to experimentally synthesizing the PP-PTO phase and to better understanding its phase transition into the converted tetragonal PbTiO 3 nanowires with enhanced piezoelectric and ferroelectric properties.
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U2 - 10.1016/j.actamat.2019.04.008
DO - 10.1016/j.actamat.2019.04.008
M3 - Article
AN - SCOPUS:85064328332
VL - 171
SP - 146
EP - 153
JO - Acta Materialia
JF - Acta Materialia
SN - 1359-6454
ER -