A Brief introduction of the Speaker
Dr Haixue Yan works on high temperature piezoelectric, Spark Plasma Sintering (SPS), phase transitions in ferroelectrics. He reported for the first-time ferroelectricity and piezoelectricity in layer-structured A2B2O7 ceramics with super-high Curie points (>1450 ℃). This work has produced a step-change in the operating temperature of piezoelectric sensors. His work on SPS has demonstrated that nano particles can work as building blocks during fast sintering. His work on ferroelectric characterization has provided evidences to answer open questions on phase transitions in lead-free ferroelectrics including Bi0.5Na0.5TiO3, NaNbO3 and AgNbO3-based dielectrics. Recently his research has focused on high entropy ferroelectric ceramics for dielectric and/or piezoelectric applications. His recent work also covers THz probing dielectrics and high entropy ceramics.
Abstract
Terahertz (THz) radiation, which lies in the frequency domain of 0.1–10 THz, has shown great potential in clinical diagnosis due to its nonionization and noninvasive detecting characteristics. Here, we describe our recent progress on the terahertz (THz) characterization of linear and nonlinear dielectrics for broadening their applications. Based on our studies on linear dielectrics, we show that THz characterization can probe the effect of porosities, point defects, shear planes, and grain boundaries on dielectric properties of ZrO2 for medical applications. Further, we demonstrate that THz measurements on relaxor ferroelectrics can be successfully used to study the reversibility of the electric field-induced phase transitions in ferroelectrics, providing guidance for improving their energy storage efficiency in capacitors. Finally, we show that THz characterization can be used to characterize the effect of domain walls on dielectric permittivity in ferroelectrics. Our studies indicate that the dipoles located within domain walls provide a lower contribution to the permittivity at THz frequencies than the dipoles present in domains. The new findings could help develop a new memory device based on nondestructive reading operations using a THz beam.
