Low-Temperature Sintering and Energy Storage Properties of Lead Lanthanum Zirconate Stannate–Titanate Antiferroelectric Ceramics

Introduction There exist severe problems in the society, i.e., environmental pollution, energy shortage, and climate change. These problems directly affect the living environment and have significant threats to globally sustainable development. In the past decades, some low-carbon new energy solutions are developed to address the continuously growing energy demand and mitigate the adverse impacts of climate change. Despite of the continuous emergence of new energy devices, it is still important to face the challenges, i.e., relatively low power density, safety, large volume, etc.. In this paper, the dielectric materials for multilayer energy storage capacitors (MLCC) were prepared by a solid-state reaction method at a lower sintering temperature with low-cost base metal electrodes (e.g., Cu). In addition, the energy storage properties of the MLCC were also characterized. Methods (Pb0.97La0.02)(Zr0.55Sn0.41Ti0.04)O3 (PLZST)–x% MgO–Al2O3–ZnO–B2O3–SiO2 (MAZBS, x=0.00, 0.25, 0.50, 0.75, 1.00, 1.25) ceramics were synthesized by a conventional solid-state reaction method. The fabricated ceramics were characterized by Fourie transformation infrared spectroscopy (FTIR), thermal analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The dielectric, ferroelectric, and energy storage properties were examined by a LCR impedance analyzer and a polarization–electric field (P–E) hysteresis loop analyzer. PbO (purity: 99.0% in mass fraction, the same below), La2O3 (99.5%), ZrO2 (99.5%), SnO2 (99.8%), and TiO2 (99.8%) were used as raw materials to synthesize PLZST. MAZBS glass powders were prepared by a water quench method. Afterwards, they were mixed with the oxides powders in a designed mass ratio, ground by high-energy ball milling for 24 h, dried at 80 ℃ for 10 h, and then sintered to form PLZST–x% MAZBS (x=0.00, 0.25, 0.50, 0.75, 1.00, 1.25) antiferroelectric ceramics. The calcined powders with 5% polyvinyl butyral (PVB) as a binder were pressed into discs with 12 mm in diameter and 1 mm in thickness at 20 MPa. Finally, the green bodies with added MAZBS glass phase were sintered at 930–1 000 ℃ for 4 h, while the sample without x was sintered at 1 200–1 300 ℃ for 2 h. For the properties test, the ceramics were firstly polished, and gold electrodes were then deposited on the both surfaces. The electrode diameter and thickness for each sample were (3.00–0.11) mm and (0.055–0.007) mm as x=0.00, (0.82–0.19) mm and (0.072–0.07) mm as x=0.25, (1.68–0.04) mm and (0.076–0.007) mm as x=0.50, (2.28–0.33) mm and (0.055–0.004) mm as x=0.75, (0.87–0.30) mm and (0.066–0.003) mm as x=1.00, (1.90–0.44) mm and (0.062–0.005) mm as x=1.25. Results and discussion The XRD patterns of PLZST–x% MAZBS (x=0.00, 0.25, 0.50, 0.75, 1.00, 1.25) antiferroelectric ceramics reveal a shift towards low angles for a peak (200) at 43°–45° when the glass content increases. This shift indicates a possible substitution of Ti4+ (with the radium of 0.60 Å) by Mg2+ (with the radium of 0.69 Å). Concurrently, the dielectric constant decreases with increasing the glass content due to the lower dielectric constant of glass. The P–E hysteresis loop results demonstrate that PLZST–x% MAZBS ceramics exhibit an optimum energy storage performance when x=0.75, and a good performance at different frequencies. However, a further increase in glass content leads to the entrance of metallic ions from the glass phase into the ceramic lattice, causing the defects and reduction of the dielectric breakdown strength of the ceramics. Conclusions The impact of MAZBS glass content on the energy storage properties of PLZST ceramics was investigated. It was indicated that an appropriate content of MAZBS glass phase could reduce the sintering temperature of PLZST ceramics from 1 200 ℃ to 930 ℃. The XRD patterns confirmed a perovskite structure of PLZST–x% MAZBS ceramics. The FTIR spectroscopy revealed the formation of non-bridging oxygen bonds due to the doping of Al3+, Zn2+, and Mg2+. The glass transition temperature and softening temperature of MAZBS glass were examined via the TG/DSC analysis. The dielectric analysis indicated a tetragonal antiferroelectric–ferroelectric phase transition with increasing the temperature, and the dielectric constant peak gradually decreased with the increase of glass content. The results of P–E hysteresis loop illustrated the electric field-induced antiferroelectric–ferroelectric phase transition characteristics of ceramics, with the maximum polarization achieved at the glass phase content of 0.75%. The PLZST–0.75% MAZBS ceramics had a maximum energy storage density of 6.08 J/cm3 and an efficiency of 77% at 300 kV/cm. This result indicated that PLZST–MAZBS ceramics could be developed into high-energy density ceramic capacitors with cost-effective copper inner electrodes. © 2024 Chinese Ceramic Society. All rights reserved.