Yuanyu Wang

Piezoelectric Properties of LiSbO3-Modified (K0.48Na0.52)NbO3 Lead-Free Ceramics

Lead-free piezoelectric (1-x)(K0.48Na0.52)NbO3–xLiSbO3 [(1-x)KNN–xLS] ceramics were prepared by conventional sintering. A morphotropic phase boundary (MPB) between the orthorhombic and tetragonal phases was identified in the composition range of 0.04<x<0.06. The ceramics near the MPB exhibit a strong compositional dependence, and good piezoelectric properties, temperature stability, and aging characteristics. It was found that the samples with 5 mol % LS exhibited enhanced electrical properties (d33~262 pC/N, kp~46%, Tc~373 °C, To–t~60 °C). These results show that (1-x)KNN–xLS ceramic is a promising lead-free piezoelectric material.

Preparation and Characterization of (1 — x) Pb(Mg1/3Nb2/3) O3 — x PbTiO3 Electrocaloric Ceramics

Lead magnesium niobate Pb(Mg1/3Nb2/3)O3 — lead titanate PbTiO3 [abbr. as (1 — x) PMN — x PT] ferroelectric ceramics with different excesses of MgO and PbO were systematically studied under different processing conditions for ferroelectric refrigeration application. It was found that the excess amount of MgO and PbO, and the sintering temperature have great effect on the crystallographic properties of the ceramics. In our experiments, (1 — x) PMN —x PT (x = 0.08, x = 0.10, and x = 0.25 respectively) with the excesses of 2 mol% MgO and 2 mol% PbO ceramics sintered at 1250 °C/1 hour possess the desired perovskite structures and large electrocaloric temperature change (ΔT = 1 K and more) in the vicinity of room temperature under a dc electric field of 1.5 kV/mm. It is expected that (1 — x) PMN — x PT electrocaloric ceramics could be applied for cascade refrigeration near room temperature.

Microstructure and electrical properties of (Li, Ag, Ta, Sb)-modified (K0.50Na0.50)NbO3 lead-free ceramics with good temperature stability

0.98[(K0.4725Na0.4725Li0.055)NbO3]–0.02Ag(Ta1−xSbx)O3 lead-free piezoelectric ceramics were prepared by the conventional mixed-oxide method. The effects of the Sb content on the microstructure and the electrical properties of the ceramics were systematically investigated. The experimental results show that Sb strongly affects the microstructure and the electrical properties of the ceramics and that the partial substitution of Sb slightly decreases the Curie temperature (Tc) and shifts the orthorhombic–tetragonal phase transition temperature (TO–T) to below room temperature. The thermal-depoling behaviour, age characteristics and temperature stability of the ceramics with x = 0.40 were also studied. The ceramics with x = 0.40 exhibit optimum properties (d33 = 250 pC N−1, kp = 44%, Tc = 444 °C, er ~ 1186, tan δ ~ 2.7%, Pr ~ 32.0 µC cm−2, Ec ~ 14.8 kV cm−1), good thermal-depoling behaviour and age characteristics and improved temperature stability. These results show that the ceramic with x = 0.40 is a promising candidate material for high-temperature lead-free piezoelectric ceramics.

Analyses and syntheses of ferroelectric refrigeration ceramics

Abstract Cryogenic refrigeration could be realized by using the electrocaloric effect (i. e. inverse pyroelectric effect) of ferroelectric materials. Recent progresses implied that ferroelectric refrigeration may be a possible new technique of cryogenic refrigeration operated near room temperature. The analyses and syntheses of ferroelectric refrigeration ceramics of PMN-PT system are presented in this paper