High Energy Storage Density and Impedance Response of PLZT2/95/5 Antiferroelectric Ceramics

Electroceramics for High-Energy Density Capacitors: Current Status and Future Perspectives

Materials exhibiting high energy/power density are currently needed to meet the growing demand of portable electronics, electric vehicles and large-scale energy storage devices. The highest energy densities are achieved for fuel cells, batteries, and supercapacitors, but conventional dielectric capacitors are receiving increased attention for pulsed power applications due to their high power density and their fast charge-discharge speed. The key to high energy density in dielectric capacitors is a large maximum but small remanent (zero in the case of linear dielectrics) polarization and a high electric breakdown strength. Polymer dielectric capacitors offer high power/energy density for applications at room temperature, but above 100 °C they are unreliable and suffer from dielectric breakdown. For high-temperature applications, therefore, dielectric ceramics are the only feasible alternative. Lead-based ceramics such as La-doped lead zirconate titanate exhibit good energy storage properties, but their toxicity raises concern over their use in consumer applications, where capacitors are exclusively lead free. Lead-free compositions with superior power density are thus required. In this paper, we introduce the fundamental principles of energy storage in dielectrics. We discuss key factors to improve energy storage properties such as the control of local structure, phase assemblage, dielectric layer thickness, microstructure, conductivity, and electrical homogeneity through the choice of base systems, dopants, and alloying additions, followed by a comprehensive review of the state-of-the-art. Finally, we comment on the future requirements for new materials in high power/energy density capacitor applications.

Giant Negative Electrocaloric Effect in Anti-Ferroelectric (Pb0.97La0.02)(Zr0.95Ti0.05)O3 Ceramics

A giant electrocaloric effect is reported in (Pb_0.97La_0.02)(Zr_0.95Ti_0.05)O₃ anti-ferroelectric ceramics. These samples were fabricated by a solid-state mixed oxide technique. Dielectric analyses were employed to investigate the anti-ferroelectric (AFE) and ferroelectric (FE) phase transitions of the sample. During the heating process, the phase transition from the orthorhombic anti-ferroelectric phase (AFE_O) to the tetragonal anti-ferroelectric phase (AFE_T) occurs at 155 °C, and the phase transition from AFE_T to PE occurs at 225 °C. Using the Maxwell relationship, the entropy change ΔS and adiabatic temperature change ΔT were obtained at different electric fields ranging from 40 to 65 kV/cm. The maximum adiabatic temperature change (ΔT _max = -7.47 K) was obtained at 50 kV/cm, which was attributed to the field-induced phase transformation between the anti-ferroelectric and ferroelectric phases. These results showed that PLZT2/95/5 ceramics possess a large negative electrocaloric effect value, which could be applied in achieving cooling power as refrigerants.

Antiferroelectric to relaxor ferroelectric phase transition in PbO modified (Pb0.97La0.02)(Zr0.95Ti0.05)O3 ceramics with a large energy-density for dielectric energy storage

The recoverable energy density and energy efficiency of the high energy density electrification PLZT2/95/5 ceramic capacitors as a function of the temperature and electric field.