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54. Achieving well-balanced performance of d33 and Td in unmodified morphotropic phase boundary BNKT20 ceramics by optimizing phase structure.

Author

Fu, Jinxin, Zhou, Changrong, Chen, Jun, Yu, Dongyan, Wu, Di, Li, Qingning, Yuan, Changlai, Xu, Jiwen, and Rao, Guanghui

Abstract

The incompatibility of the large piezoelectric response (d33) and high depolarization temperature (Td) in lead-free piezoelectric ceramics limited their practical applications. The most used modification methods for improving d33 or Td commonly required a delicate control of complex compositions. Here, a strategy for simply changing the sintering temperature is used to defer the Td and increase d33 simultaneously. The Td and d33 of unmodified Bi0.5Na0.5TiO3-0.2Bi0.5K0.5TiO3 (BNKT20) ceramics increase with increasing sintering temperature until both of them reach the maximum (d33 ~ 174pC/N, Td ~ 177 °C) at the sintering temperature of 1100 °C. In-depth analysis unveils the critical role of multiphase coexistence and oxygen vacancies in enhancing Td by optimizing sintering temperature. Meanwhile, increasing sintering temperature promotes large grain size with easy domain orientation, thus, yielding the improved d33. This work provides a simple and effective method to broaden the working range of Bi0.5Na0.5TiO3-based (BNT) piezoelectric ceramics at high temperature under the premise of realizing high piezoelectric properties. [ABSTRACT FROM AUTHOR]

Published
2024
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82. Characterization and luminescence properties of CaMgGe2O6: Mn2+ NIR-I mechanoluminescence phosphor.

Author

Zhang, Zeqing, Liu, Wei, Li, Lin, Li, Huan, Zhang, Zhijun, Cheng, Shuai, Rao, Guanghui, and Zhao, Jingtai

Abstract

In recent years, materials exhibiting multimodal luminescence properties from deep red to near-infrared (NIR) wavelengths have been a focal point of research, particularly in the exploration of applications within the realms of stress sensing and dynamic signature anti-counterfeiting. A pyroxene-type layered crystal structure compound, CaMgGe2O6: Mn2+, has been reported as a mechanoluminescent (ML) material. Upon incorporation into the host, Mn2+ ions preferentially substitute for Mg2+ ions, emitting deep red to near-infrared light (600–800 nm) within this six-coordinated [MgO6] octahedral environment. The congruence of photoluminescence and ML spectra indicates that both types of luminescence originate from the same emissive center. The doping of Mn2+ ions introduces impurity band, effectively reducing the optical band gap, as evidenced by ultraviolet diffuse reflectance measurements. Thermoluminescence results reveal three defect centers within the phosphor, whose concentrations decrease with Mn2+ doping, correlating with a reduction in ML intensity. The ML mechanism of the phosphor is elucidated through the analysis of local piezoelectric properties within the crystal. Overall, this study may pave new pathways for the development of efficient near-infrared mechanoluminescent materials, showcasing potential applications within the biological domain. [ABSTRACT FROM AUTHOR]

Published
2024
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83. The Effect of Multi‐Fields Synergy from Electric/Light/Thermal/Force Technologies on Photovoltaic Performance of Ba0.06Bi0.47Na0.47TiO3 Ferroelectric Ceramics via the Mg/Co Substitution at A/B Sites.

Author

Gao, Qingyuan, Yang, Shanming, Yuan, Changlai, Liu, Xiao, Zhao, Jingtai, Rao, Guanghui, Zhou, Changrong, Xu, Jiwen, Zhu, Baohua, and Lei, Wen

Subjects
FERROELECTRIC materials, FERROELECTRIC ceramics, FERROELECTRICITY, PHENOMENOLOGICAL theory (Physics), ELECTRIC fields, PHOTOVOLTAIC effect
Abstract

Currently, it is widely reported that the photovoltaic effect in ferroelectric materials can be promoted by the application of a piezoelectric force, an external electric field, and intense light illumination. Here, a semiconducting ferroelectric composition is introduced, (1−x) Ba0.06Bi0.47Na0.47TiO3‐xMgCoO3 (abbreviated as xMgCo, where x = 0.02–0.08), synthesized through Mg/Co ions codoping. This process effectively narrows the optical bandgaps to a spectrum of 1.38–3.06 eV. Notably, the system exhibits a substantial increase in short‐circuit photocurrent density (Jsc), by the synergy of the electric, light, and thermal fields. The Jsc can still be further enhanced by the extra introduction of a force field. Additionally, the Jsc also shows an obvious increase after the high field pre‐poling. The generation of a considerable number of oxygen vacancies due to the Co2+/Co3+ mixed valence state (in a 1:3 ratio) contributes to the reduced optimal bandgap. The integration of Mg2+ ion at the A‐site restrains the loss and sustains robust ferroelectricity (Pr = 24.1 µC cm−2), high polarizability under an electric field, and a significant piezoelectric coefficient (d33 = 102 pC N−1). This study provides a novel perspective on the physical phenomena arising from the synergy of multiple fields in ferroelectric photovoltaic materials. [ABSTRACT FROM AUTHOR]

Published
2024
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