Ce and Y Co-Doping Effects for (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 Lead-Free Ceramics

CeO2 and Y2O3 were co-doped to (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramics and sintered by conventional solid-state reaction process to form x wt.% CeO2-y wt.% Y2O3 doped (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (CexYy-BCZT) ceramics. The effects of different contents of CeO2-Y2O3 dopants to the (Ba0.85Ca0.15) (Zr0.1Ti0.9)O3 composition were analyzed by studying the phase, surface microstructure, piezoelectric and ferroelectric properties of BCZT ceramics. In this study, we have shown that co-doping a small amount of CeO2 and Y2O3 will not change the phase structure of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramics. However, the proper introduction of CeO2 and Y2O3 can improve the piezoelectric constant and electromechanical coupling coefficient of BCZT ceramic samples. Moreover, these dopants can promote the grain growth process in (Ba0.85Ca0.15) (Zr0.1Ti0.9)O3 ceramics. C0.04Y0.02 doped (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramic has the best piezoelectric properties compared with other composition, the results are as follows: Relative density = 96.9%, Kp = 0.583, and d33 = 678 pC/N, V = 8.9 V. It means that this Ce0.04Y0.02 doped (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramic is a desired material in the application of lead-free ceramics.

Thermal-stability of the enhanced piezoelectric, energy storage and electrocaloric properties of a lead-free BCZT ceramic

High-thermal stability of the recovered energy density and significant electrocaloric temperature change over a broad temperature span in a lead-free BCZT ceramic.

Structure and electrical properties of BCZT ceramics derived from microwave-assisted sol–gel-hydrothermal synthesized powders

A novel microwave-assisted sol–gel-hydrothermal method was employed to rapidly synthesize Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) powders. The effects of reaction time on the structure, crystallinity, purity and morphology of the products were investigated. The results of XRD, FTIR, SEM and TEM indicated that BCZT powders could be obtained in even 60 min at a low synthesis temperature of 180 °C, which were well-crystallized with stoichiometric composition and uniform grain size (~ 85 nm). BCZT ceramic derived from the rapidly-synthesized powders had a dense microstructure and good electrical properties (εm = 9579, d33 = 496 pC/N, 2Pr = 25.22 µC/cm2, 2Ec = 7.52 kV/cm). The significant electrical properties were closely related to the high activity of the BCZT powders, resulting from the rapid microwave-assisted sol–gel-hydrothermal process.

Thermally-stable high energy storage performances and large electrocaloric effect over a broad temperature span in lead-free BCZT ceramic

Thermally-stable recovered energy density and significant electrocaloric temperature change over a broad temperature span in BCZT ceramic elaborated by low-temperature hydrothermal processing.

Dielectric and piezoelectric properties of porous lead-free 0.5Ba(Ca0.8Zr0.2)O3-0.5(Ba0.7Ca 0.3)TiO3 ceramics

Porous barium calcium zirconate titanate 0.5Ba(Ca0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT) lead-free ferroelectric ceramics were fabricated via a burnt polymer spheres (BURPS) technique by introducing corn starch as the pore-forming agent. The effect of porosity on the microstructure, dielectric, and piezoelectric properties of the porous materials were investigated. An increase in porosity from 10 % to 25 % resulted in an increase in the hydrostatic charge coefficient (dh), which was 140 to 560 % higher than that of the dense BCZT material. An increase in porosity from 10 % to 25 % also lead to a decrease in relative permittivity that was 16.7% to 60.4% lower than the dense material. These two changes in properties provided a significant enhancement of the hydrostatic figure of merit (dh·gh) for the porous ceramic; for example the dh·gh of the 25 vol.% porous BCZT ceramic was 158 times more than the dense ceramic and demonstrates the potential of porous lead-free ferroelectrics for piezoelectric transducer devices. Reasons for the significant enhancement in piezoelectric performance of the porous ceramics are discussed.

Phase Structure, Microstructure and Electrical Properties of BCZT Ceramics Prepared by Seed-Induced Method

The effect of particle sizes of CaZrO3 (CZ) nanocrystal on the phase structure, microstructure and electrical properties of Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) was studied. The CaCO3 and ZrO2 were used as starting materials for CaZrO3 (CZ) seeds synthesized by the molten-salt method. The results were found that the CZ powder has a pure perovskite with the particle size about 370 to 460 nm. Then the CZ nanocrystals were mixed with the metal oxides BaCO3, CaCO3, ZrO2 and TiO2 by mixed oxide method. The phase structure, microstructure and electrical properties of BCZT ceramic were investigated as a function of particle size and concentration of CZ. The results indicated that all samples showed pure perovskite phase. The highest values of density, grain size, dielectric constant (εr) and piezoelectric coefficient (d33) were 5.50 g/cm3, 10.95 μm, 2992 and 446 pC/N, respectively which obtained at the CZ seed size 459 nm.

Effect of External Fields on the Switching Current in (Ba0.97Ca0.03) (Zr0.18Ti0.82) O3 Ceramics

Lead-free (Ba0.97Ca0.03) (Zr0.18Ti0.82) O3(BCZT) ceramic is prepared by sol-gel technique. The sample shows a pure perovskite structure through the XRD pattern. Well-developed grain morphology and a dense microstructure are acquired at an optimistic sintering temperature (~1330°C). The BCZT ceramic shows a surprisingly high piezoelectric coefficient of d33=675 pm/V. The switching current curves are acquired in the different external fields by TF-2000 Ferroelectric Analyzer. It is found that with increasing the temperature, there is a decrease in the coercive field (Ec), and with increasing the electric field, there is an increase in the switching current obviously. Sintering temperature has an effect on switching current. The effect of temperature and electrical field on switching current is analyzed from viewpoint of the energy.