Researchers have achieved ultra-low energy loss, lead-free high-temperature dielectric ceramic capacitors

High-efficiency energy storage technology has been widely concerned by academia and business, and the development of energy storage ceramic capacitors as the core components of pulsed power electronics applications is of great significance. Compared with other currently available energy storage devices (batteries, fuel cells and supercapacitors), its advantages include fast charging/discharging capabilities, higher power density and longer life, which are decisive for the development of advanced power electronic equipment towards miniaturization and integration. However, low energy density and/or low energy efficiency and temperature instability are major obstacles to promoting the practical application of dielectric ceramic capacitors.

Relaxation ferroelectric materials RFEs are considered to be candidates with great optimization potential for high-performance capacitors, and the currently accepted method of enhancing relaxation behavior is to induce disordered structures or nanodomains such as BT-BaZrO3 and BF-SrTiO3 by introducing paraelectric or linear end elements into FEs. Similarly, by introducing the paraelectric component SrTiO3(ST) or Sr2+ to the A site of BNT ceramics with R-phase at room temperature, the coexistence structure of rhomboid (R3c,R) and tetragonal (P4bm,T) phase nanodomains can be achieved in BNT-ST relaxation systems. It is worth noting that in the polymorphic nanodomain structure, the polarization anisotropy and energy barrier are significantly damaged, resulting in a smoother transition of polarization under the electric field than in the single-phase nanodomain. However, some preliminary work has found that excessive introduction of Sr2+ leads to large Pmax losses and limits the optimization of energy storage performance. Therefore, harmonizing the proportion of polymorphic nanodomains to increase Pmax-Pr value and optimizing the preparation process to improve the breakdown field strength are the research focuses of this work.

In response to this problem, Professor Di Zhou’s team from the School of Electronic Science and Engineering, Faculty of Telecommunications, Xi’an Jiaotong University, designed a heterostructure in which R-phase and T-phase polar nanomicroregions (PNRs) are embedded in the C-phase quasi-electric matrix. The results show that with the increase of chemical complexity of the relaxation system, the degree of polarization disorder intensifies, and the induced polymorphic PNRs greatly optimize the energy storage performance and can achieve superior temperature insensitivity. In addition, the system maintains an ultra-high Wrec value of 10.28 J·cm-3 and a η value (97.11%) comparable to lead-based ceramics, which is better than other lead-free systems reported so far, especially its energy loss is extremely low. The ceramic has high performance and stability in a wide temperature range (25-200 °C) (Wrec~6.35±9% J·cm-3, η~94.8%±3%). These results suggest that this multicomponent design can be considered a viable example for developing RFEs for the next generation of high-performance energy storage applications, and may arouse general interest in material design in other fields.

Energy storage characteristics of BMT15-RRP ceramics under different test conditions (electric field, temperature, frequency and number of cycles). (Photo courtesy of the research team)

The research results are titled “A lead-free high-temperature ceramic capacitor with near-zero energy loss” and published online in the internationally renowned journal Energy and Environmental Science. Xi’an Jiaotong University is the only communication unit, Li Da, a doctoral student in the School of Electronics, Faculty of Telecommunications, is the first author, Professor Zhou Di of the School of Electronics, Assistant Professor Xu Diming of the School of Electronics and Professor Wang Dong of the Frontier Institute are the co-corresponding authors. (Source: Yan Tao, China Science News)

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