Du Hongliang

Effects of (LiCe) co-substitution on the structural and electrical properties of CaBi2Nb2O9 ceramics

The piezoelectric, dielectric, and ferroelectric properties of the (LiCe) co-substituted calcium bismuth niobate (CaBi2Nb2O9, CBNO) are investigated. The piezoelectric properties of CBNO ceramics are significantly enhanced and the dielectric loss tan δ decreased. This makes poling using (LiCe) co-substitution easier. The ceramics (where represents A-site Ca2+ vacancies, possess a pure layered structure phase and no other phases can be found. The Ca0.88(LiCe)0.040.04Bi2Nb2O9 ceramics possess optimal piezoelectric properties, with piezoelectric coefficient (d33) and Curie temperature (TC) found to be 13.3 pC/N and 960 °C, respectively. The dielectric and piezoelectric properties of the (LiCe) co-substituted CBNO ceramics exhibit very stable temperature behaviours. This demonstrates that the CBNO ceramics are a promising candidate for ultrahigh temperature applications.

Achieving a multi-band metamaterial perfect absorber via a hexagonal ring dielectric resonator*

A multi-band absorber composed of high-permittivity hexagonal ring dielectric resonators and a metallic ground plate is designed in the microwave band. Near-unity absorptions around 9.785 GHz, 11.525 GHz, and 12.37 GHz are observed for this metamaterial absorber. The dielectric hexagonal ring resonator is made of microwave ceramics with high permittivity and low loss. The mechanism for the near-unity absorption is investigated via the dielectric resonator theory. It is found that the absorption results from electric and magnetic resonances where enhanced electromagnetic fields are excited inside the dielectric resonator. In addition, the resonance modes of the hexagonal resonator are similar to those of standard rectangle resonators and can be used for analyzing hexagonal absorbers. Our work provides a new research method as well as a solid foundation for designing and analyzing dielectric metamaterial absorbers with complex shapes.

Effects of A -site equivalence and non-equivalence substitution on polarization properties of K 0.5 Na 0.5 NbO 3 lead-free piezoelectric ceramics

The effects of A -site equivalence and non-equivalence substitution on polarization temperature and electric field of K 0.5 Na 0.5 NbO 3 lead-free piezoelectric ceramics are studied, and the results show that the ceramics sample of A -site equivalence is independent of polarization temperature and electric field, which can improve the piezoelectric constant. On the contrary, the ceramics sample of A -site non-equivalence substitution is sensitive to polarization temperature and electric field, constraining the piezoelectric properties.