Compared to batteries and electrochemical capacitors, dielectric capacitors are widely studied because of their huge advantages in terms of charging/discharging speed and power density. In this work, high-entropy (Bi_0.2Na_0.2Sr_0.2Ba_0.2Ca_0.2)TiO₃ lead-free relaxor-ferroelectric ceramics were prepared by both conventional sintering (CS) and spark plasma sintering (SPS). The results showed that the ceramic prepared by SPS obtained a high energy storage density of 6.66 J/cm³ and a satisfied energy storage efficiency of 77.2% under an electric field of 430 kV/cm. This is directly related to the high density, fine grains, number of oxygen vacancies, and composition uniformity of the SPS samples. This study provides a new path for the preparation of high-entropy dielectric energy storage ceramics with high energy storage properties.

Piezoelectric ceramics have been widely used in high precision sensors such as vibration detection, but piezoelectric accelerometers in high temperature applications are very rare. We prepared (1-x)BiFeO3-xBaTiO3-0.0035MnO2-0.001Li2CO3(BF-xBT) ceramics by a solid state approach, and investigated the effect of BT content(x) on the phase structure, microstructure, dielectric properties, ferroelectric properties, piezoelectric properties, temperature stability and especially the sensitivity of the piezoelectric accelerometer. The crystal structure of the sample is pure perovskite structure with the MPB (R and P phases) locating in a composition range of 0.28 ≤ x ≤ 0.32 for BF-xBT ceramics, and the single R phase exist at 0.20 ≤ x < 0.28. When x = 0.30, the ceramic presents both high Curie temperature and d33. Notably, the sensitivity of BF-0.30BT piezoelectric accelerometer reaches the highest value of about 40 pC/g and shows an excellent stability until 400 °C, indicating that this material is a promising candidate for high-temperature piezoelectric accelerometer applications.