Processing and Characterization of BCZT-Modified BiFeO3-BaTiO3 Piezoelectric Ceramics

The synthesis of non-lead piezoelectric ceramics (1–z)(0.65Bi1.05Fe2O3-0.35BaTiO3)-z Ba(Ti0.8Zr0.2)O3-(Ba0.7Ca0.3)TiO3 using a solid state method and a quenching strategy was investigated. The processing conditions such as the sintering temperature and soaking time were optimized. The patterns of X-ray diffraction (XRD) displayed a pure perovskite structure with no secondary phases. The ferroelectric and piezoelectric characteristics of the samples were considerably improved as a result of the lattice strain. The findings of the experiment revealed that the quenching technique increases the piezoelectric sensor constant of 152 pC/N in optimized conditions. The enhanced piezoelectric sensor constant (d33) value at z = 0.020 was ascribed to the incorporation of multi-cationic BCZT, which modified the bond lengths at a unit cell level and gave rise to more flexibility in complex domain switching. This facilitated easier domain alignment in response to the applied field and resulted in an improvement in the electrical properties.

PMN-PSMNT ceramics fabricated using the twin-crystal mixed co-firing method

(1-w)[Pb(Mg1/3Nb2/3)0.67Ti0.33O3]-w[Pb1 − 1.5xSmx(Mg1/3Nb2/3)yTi1−yO3] ((1-w)PMN-wPSMN-PT) piezoelectric ceramics were prepared using the newly proposed twin-crystal mixed co-firing method in which two pre-sintered precursor powders were mixed and co-fired with designated ratios (w = 0.3, 0.4, 0.5, 0.6). X-ray diffraction results show that all the samples presented a pure perovskite structure. The grains were closely packed and the average size was ~ 5.18 µm from the observations of scanning electron microscopy images, giving the high density of ceramics to be 97.8% of the theoretical one. The piezoelectric, dielectric, and ferroelectric properties of the ceramic samples have been investigated systematically. It was found that the performance of ceramics was significantly enhanced when compared to the ceramics fabricated using the conventional one-step approach. Outstanding piezoelectric coefficient d33 of 1103 pC/N and relative dielectric permittivity εr of 9154 could be achieved for the ceramics with w = 0.5.

Excellent Energy Storage Performance in NaNbO3-Based Relaxor Antiferroelectric Ceramics Under a Low Electric Field

NaNbO3-based antiferroelectric (AFE) ceramics have the prominent advantages of stable performance and low cost. However, its energy storage property is often remarkably limited by the hysteresis of the antiferroelectric to ferroelectric phase transformation. In this work, 0.88Na(Nb1 − xTax)O3–0.12Bi0.2Sr0.7TiO3 (x = 0–0.075) antiferroelectric ceramics were synthesized using a conventional mixed oxide route. Ta5+ were completely dissolved into the lattice of 0.88NaNbO3–0.12Bi0.2Sr0.7TiO3 to form a pure perovskite structure. With increased Ta content, the AFE orthogonal P phase was replaced by AFE orthogonal R phase progressively. Meanwhile, the dielectric constant curve showed relaxor-like properties. As a result, slender P–E curves with reduced hysteresis loss and decreased residual polarization were achieved. Interestingly, a large recoverable energy storage density (Wrec ≈ 2.16 J cm− 3) and high energy storage efficiency (η ≈ 80.7%) were obtained simultaneously under a low driving electric field of 15 kV mm− 1 at doping ratio (x) of 0.075. In addition, the 0.88Na(Nb0.925Ta0.075)O3–0.12Bi0.2Sr0.7TiO3 sample exhibited excellent temperature stability, indicating an ideal candidate in future pulsed power capacitor.

Microstructure and Piezoelectric Properties of 0.97(Na, K, Li)(Nb, Sb, Ta)O3-0.03(Bi, Na, Sr)ZrO3 Ceramics Doped with Boron Oxide for Piezoelectric Actuator

In this study, with the motivation of developing low temperature sintered Pb-free ceramics for use in piezoelectric actuators, 0.97(Na0.52K0.443Li0.037)(Nb0.923Sb0.04Ta0.037)O3 − 0.03 (Bi0.5Na0.5)0.9 (Sr)0.1ZrO3 ceramics were manufactured and their piezoelectric properties analyzed. All specimens doped with boron oxide showed a typical pure perovskite structure. The ceramics with x = 0.1 composition showed a co-existence of R-T phases. When boron oxide is doped at 0.1 wt%, excellent physical properties of d33 = 270 pC/N εr = 1386, kp = 0.416, and Qm = 130 were obtained making the ceramic ideal for use in piezoelectric actuators.

Doping effects in (Ba0.85Ca0.15)(Hf0.1Ti0.9)O3 lead-free piezoelectric ceramics prepared via powder injection moulding using simple binder

To improve densification of the (Ba0.85Ca0.15)(Hf0.1Ti0.9)O3 (BCHT) ceramics prepared via powder injection moulding, MnO2 and Li2CO3 were used as sintering aids. The BCHT ceramics doped with different Mn- and Li-amount prepared by powder injection moulding in which paraffin was used as injection binder, have rather pure perovskite structure with complicated polymorphic ferroelectric phase coexistence. Polyhedral grains combined with nearly round shape grains with increased relative density and larger gains size were obtained at appropriate doping amount, related to the formation of liquid phase during sintering and increased mobility of ions due to the generation of point defects caused by heterovalent cations doping. TheMn- and Li-doped BCHT ceramics are displacement driven ferroelectrics with apparent diffused transition characteristic at different extent, relating to the morphotropic phase boundary composition and the variation of point defects induced by doping. Comparable or surpassing electrical performance was acquired, especially the dielectric breakdown strength was increased due to the improved sinterability. With appropriate doping amount, piezoelectricity larger than 300 pC/N can be obtained in the Mn- and Li-doped BCHT ceramics poled under low electric field.

Fabrication and performance of PNN-PZT piezoelectric ceramics obtained by low-temperature sintering

The Pb(Ni1/3Nb2/3)O3-Pb(ZrxTi1−x)O3 (PNN-PZT) piezoelectric ceramics with CuO and LiBiO2 doping were successfully fabricated by the low-temperature solid-state reaction to effectively restrain the PbO volatilization. The microstructure and electrical properties of the PNN-PZT ceramics were characterized. The experimental results reveal that the PNN-PZT ceramics are composed of a pure perovskite structure in which the rhombohedral and tetragonal phases coexist. Meanwhile, the good electric properties, including low dielectric loss, outstanding diffusion phase transition and palpable dielectric relaxation, are exhibited in PNN-PZT ceramics with 0.2 wt.% CuO and 1 wt.% LiBiO2 addition. This piezoceramic composition possibly provides a reference for the application of multi-layer piezoelectric actuators.

Enhanced ferro-/piezoelectric properties of tape-casting-derived Er3+-doped Ba0.85Ca0.15Ti0.9Zr0.1O3 optoelectronic thick films

Er3+-doped Ba0.85Ca0.15Ti0.9Zr0.1O3 (xEr-BCTZ, x = 0, 0.005, 0.01, 0.015) multifunctional thick films were prepared by the tape-casting method, using sol-gel-derived nano-sized powders as the matrix material. The surface morphologies, photoluminescence, and electrical properties were investigated. Dense microstructures with pure perovskite structure were obtained in the thick films. By doping an appropriate amount of Er3−, the samples exhibit superior up-conversion photoluminescence performance and simultaneously enhanced electrical performances. In addition, relatively higher texture fractions (with the largest value of 83.5%) were realized through introducing plate-like BaTiO3 templates to make the thick film grow by the [001]c orientation. And the ferro-/piezoelectric properties of the thick films were further improved, showing potential in the applications of micro-optoelectronic devices.

Pb(Er1/2Nb1/2)O3–Pb(Zn1/3Nb2/3)O3–PbTiO3 Single Crystals with High Curie Temperature

In this work, 0.15Pb(Er1/2Nb1/2)O3–0.63Pb(Zn1/3Nb2/3)O3–0.22PbTiO3 (15PEN–63PZN–22PT) single crystals with a pure perovskite structure are obtained through the flux method. The phase structure, dielectric, ferroelectric properties and upconversion photoluminescence of the crystals are studied. The ternary crystals along the [110] orientation have a high Curie temperature (Tc = 250 °C) and large coercive field (Ec = 11.0597 kV/cm) which are higher than those of crystals reported previously. Furthermore, the PEN–PZN–PT crystals are produced with a strong green light excited by a 980 nm laser. Being in the range 298–478 K, the emission intensity of all peaks decreases with increase in temperature. The absolute quantum yield (QY) for the crystals is 0.00059%. These excellent properties provide new possibilities for multifunctional materials of optoelectronic devices.

Structural, microstructural and dielectric properties of Ba1−xLaxTi(1−x∕4)O3 prepared by sol gel method

Detailed structural and dielectric properties of Lanthanum-doped barium titanate [Formula: see text]Lax[Formula: see text]O3 ceramic powders BLTx (where [Formula: see text]; 0.10; 0.20; 0.30 and 0.40)/BT, BLT10, BLT20, BLT30 and BLT40, synthesized by the sol gel process, calcined at 900∘C for 3[Formula: see text]h and sintered at 1250∘C for 6[Formula: see text]h, have been investigated. The phase formation and crystal structure of the samples were checked by X-ray diffraction (XRD) and Raman spectroscopy. The samples crystallize in the pure perovskite structure that transforms from tetragonal to pseudocubic under doping with La; results that have been confirmed by Rietveld Refinement technique. The estimated average crystallite size of the samples was about 23[Formula: see text]nm. Dielectric parameters (dielectric permittivity and losses) were determined in the temperature range room temperature (RT) — 280∘C and in the frequency range 500[Formula: see text]Hz–2[Formula: see text]MHz. La doping gives rise to a strong decrease of the ferro-to-paraelectric transition temperature, and the frequency dependence of the permittivity shows that the samples with [Formula: see text] and [Formula: see text] reach their resonance frequency. The frequency dependence of impedance and electric modulus properties were studied over a wide frequency range from 1[Formula: see text]kHz to 2[Formula: see text]MHz at various temperatures to confirm the contributions from grains and grain-boundaries. The complex impedance analysis data have been presented in the Nyquist plot which is used to identify the corresponding equivalent circuit and fundamental circuit parameters; it was found that the grain boundaries resistance is dominant at room temperature. The frequency dependence of the parameters permittivity, losses and AC conductivity reveals that the relaxation process is of the Maxwell–Wagner type of interfacial polarization.

Analogous Anti-Ferroelectricity in Y2O3-Coated (Pb0.92Sr0.05La0.02)(Zr0.7Sn0.25Ti0.05)O3 Ceramics and Their Energy-Storage Performance

Antiferroelectric analogous (Pb0.92Sr0.05La0.02)(Zr0.7Sn0.25Ti0.05)O3 (PSLZSnT) ceramics were prepared by the solid-state sintering method by introducing a Y2O3-coating via the self-combustion method. The synthesized Y2O3-doped PSLZSnT ceramics present pseudo-cubic structure and rather uniform microstructural morphology accompanied by relatively small grain size. Excellent energy-storage performance is obtained in the Y2O3-doped PSLZSnT ceramics, in which the value of the energy-storage density presents a linearly increasing trend within the electric field measurement range. Such excellent performance is considered as relating to the rather pure perovskite structure, high relative density accompanied by relatively small grain size, and the antiferroelectric-like polarization-electric field behavior.