TY - JOUR
T1 - Polarization stability and its influence on electrocaloric effects of high entropy perovskite oxide films
AU - Son, Yeongwoo
AU - Udovenko, Stanislav
AU - Ayyagari, Sai Venkata Gayathri
AU - Barber, John P.
AU - Nakamura, Kae
AU - Rost, Christina M.
AU - Alem, Nasim
AU - Trolier-McKinstry, Susan E.
N1 - Publisher Copyright:
© 2024 Acta Materialia Inc.
PY - 2025/1/15
Y1 - 2025/1/15
N2 - In principle, the configurational entropy inherent in High Entropy Oxides (HEOs) could facilitate large electrocaloric effects (ECE) by promoting polar entropy. In this study, it is demonstrated that the time stability of the remanent polarization can be tuned via B-site disorder in High Entropy Perovskite Oxides (HEPO) films. Eight HEPO powders were synthesized; the propensity for perovskite phase formation was consistent with the Goldschmidt tolerance factor. While entropic contributions stabilize HEPO, they do not fully predict the stabilization. Relative dielectric permittivities between 2000 and 600 can be achieved for the B-site disordered HEPO films with loss tangents below 6 % at room temperature. All films showed similar polarization-electric field loops with maximum polarization up to 48 μC cm−2 and a remanent polarization ≥ 20 μC cm−2 measured at room temperature with applied electric field of 1100 kV cm−1 at a frequency of 10 kHz. The temperature of the dielectric maximum (Tmax) increased from 105 °C to 225 °C with increasing average ion size on the B-site. Polarization stability of the HEPO films was investigated using Positive-Up-Negative-Down (PUND) measurements. It was found that in some HEPO films, 24 % of the remanent polarization decayed within 2 s. By employing the time stability of the remanent polarization, enhanced electrocaloric effects of HEPO film was predicted to be 14.9 K and 11.5 J Kg−1 K−1 at an applied field of 1120 kV cm−1, for electrocaloric temperature change and entropy change, respectively.
AB - In principle, the configurational entropy inherent in High Entropy Oxides (HEOs) could facilitate large electrocaloric effects (ECE) by promoting polar entropy. In this study, it is demonstrated that the time stability of the remanent polarization can be tuned via B-site disorder in High Entropy Perovskite Oxides (HEPO) films. Eight HEPO powders were synthesized; the propensity for perovskite phase formation was consistent with the Goldschmidt tolerance factor. While entropic contributions stabilize HEPO, they do not fully predict the stabilization. Relative dielectric permittivities between 2000 and 600 can be achieved for the B-site disordered HEPO films with loss tangents below 6 % at room temperature. All films showed similar polarization-electric field loops with maximum polarization up to 48 μC cm−2 and a remanent polarization ≥ 20 μC cm−2 measured at room temperature with applied electric field of 1100 kV cm−1 at a frequency of 10 kHz. The temperature of the dielectric maximum (Tmax) increased from 105 °C to 225 °C with increasing average ion size on the B-site. Polarization stability of the HEPO films was investigated using Positive-Up-Negative-Down (PUND) measurements. It was found that in some HEPO films, 24 % of the remanent polarization decayed within 2 s. By employing the time stability of the remanent polarization, enhanced electrocaloric effects of HEPO film was predicted to be 14.9 K and 11.5 J Kg−1 K−1 at an applied field of 1120 kV cm−1, for electrocaloric temperature change and entropy change, respectively.
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U2 - 10.1016/j.actamat.2024.120576
DO - 10.1016/j.actamat.2024.120576
M3 - Article
AN - SCOPUS:85209929994
SN - 1359-6454
VL - 283
JO - Acta Materialia
JF - Acta Materialia
M1 - 120576
ER -