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The 5.4BiScO3−(94.6-x)PbZrO3−xPbTiO3 (43.0 < x < 51.0 mol%) ternary piezoelectric ceramics were synthesized by solid-state reaction method. Phase transition from rhombohedral to tetragonal structure was identified by X-ray diffraction. In combination with piezoelectric and dielectric properties, the morphotropic phase boundary (MPB) composition was confirmed in 5.4BiScO3−47.6PbZrO3−47.0PbTiO3 ceramic with optimal piezoelectric coefficient d33 of 474 pC/N, relative dielectric constant er of 1666, mechanical coupling factor kp of 0.64 and mechanical quality factor Qm of 415 at room temperature. Besides, the 5.4BiScO3−47.6PbZrO3−47.0PbTiO3 ceramic retained most of the piezoelectric properties in broad temperature range between 40 and 300 °C, which exhibited excellent thermal stability. There were only gentle variations in d33 (Δd33/d33 = 10.6%), kp (Δkp/kp = 14.1%), Qm (ΔQm/Qm = 10.3%), and er (∂e/∂T = 13.2/°C) at 300 °C, indicating BiScO3 doping in PbZrO3−PbTiO3 binary system could form a potential candidate for high temperature applications.

In Poly(vinylidene fluoride) (PVDF) polymer films, α-phase usually dominates and leads to weak electrical properties, limiting its applications in microelectronics. In this paper, the effects of dipole moment of the solvent and the crystallization temperature on β-phase content in PVDF films have been systematically investigated. Variations in crystalline phases were confirmed by using X-ray diffractometer (XRD), Fourier transform infrared spectra (FTIR) and differential scanning calorimetry (DSC). The results verified that larger dipole moment of the solvent is more beneficial to the formation of β-phase in PVDF films. PVDF films with high content of β-phase up to 98.8% are obtained by using dimethylsulfoxide (DMSO) as the solvent at optimized crystallizing temperature of 60 °C. The corresponding PVDF film with high β-phase content presents excellent ferroelectric and piezoelectric properties, with a remnant polarization (Pr) and piezoelectric coefficient (d33) of 7.7 μC/cm2 and − 25.8 pC/N, respectively. It is worth mentioning that this high d33 compares that of the expensive PVDF-based copolymers and complexes. The process displayed in this research provided a feasible method to the preparation of low cost PVDF films for flexible piezoelectric sensors and actuators.

The structure and electric properties of 5 mol. % LiNbO3 doped xBiScO3–(95-x)PbTiO3 (5LN–xBS–(95-x)PT, 26 ≤ x ≤ 41 mol. %) ceramics have been systematically investigated. The composition-, temperature- and electric-field-dependent phase transitions were established carefully by the temperature-dependent dielectric measurements. The results verified that the 5LN–xBS–(95-x)PT system transformed to nonergodic relaxors (NR) phase gradually from normal ferroelectrics (FE) phase with the addition of BiScO3 contents. With the increase of temperature, ergodic relaxors (ER) phase was observed before the phase transition from FE and/or NR to paraelectrics (PE) phase. By comparing the dielectric responses of the ceramics before and after polarization, it was confirmed that the electric field could induce a phase transition from NR to FE while the ceramics were polarized, which was attributed to the growth of the dipole clusters and the permutation of the macroscopical ferroelectric order under the external electric field. The phase diagram of 5LN–xBS–(95-x)PT system was then built and the morphotropic phase boundary (MPB) between tetragonal and rhombohedral phase of the system was identified at 34 ≤ x ≤ 36. The optimal properties were found at the composition of 5LN–34BS–61PT ceramic with piezoelectric coefficient d33 value of 514 pC/N, planar electromechanical coupling factor kp of 0.47, relative dielectric constant er of 2511, and remnant polarization Pr of 37.4 μC/cm2. The displayed piezoelectric properties could provide alternative compositions with less lead contents comparing with the Pb(Zr, Ti)O3 based piezoceramics.

0.025LiNbO3 (LN) modified 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (BNT-BT) ceramics with micrometer-size and nanometer-size grains have been prepared by conventional soild state sintering (CS) and spark plasma sintering (SPS) processes, respectively. Comparing with the CS sample, the SPS sample presents a smaller dielectric constant but a larger piezoelectric constant and a lower triggering electric field. At room temperature, the maximum strain of the SPS ceramic is up to 0.64% at 50 kV/cm electric field, the corresponding d*33 reaches the maximum value of 1280 pm/V, which is much higher than that of the CS ceramic and also the ever reported lead-free polycrystalline ceramics. Morever, the strain hysteresis of the SPS ceramic is only 19.5%, while the ceramics prepared by CS process show a much larger strain hysteresis of 58.5%. Thus, the LN doped BNT-BT ceramics with nano grains can achieve maximum strain in designing high-precision devices and actuators with small hysteresis.

Lead-free (1 − x)(0.8Bi0.5Na0.5TiO3–0.2SrTiO3)–xLiNbO3 (BNST–xLN, x = 0–0.08) piezoelectric ceramics were fabricated by a solid-state sintered technology. The effects of LN-doping on the structural and electrical properties of the BNST–xLN system were systematically investigated. The results of Raman spectroscopy revealed that the substitution of LN softens the phonon vibrations in the BNST–xLN system, in accordance with the remarkable reduction in the phase transition temperature (TF−R), remnant polarization (Pr), negative strain (Sneg) and piezoelectric coefficient (d33). However, the degradation of the long-range ferroelectric orders was accompanied by a significant increase in the electric field–induced strain response. At x = 0.04, a maximum unipolar strain of ~ 0.36% with a corresponding normalized strain (Smax/Emax) of ~ 600 pm/V was obtained at room temperature, which should be mainly ascribed to the reversibly electric field-induced phase transition between the ergodic relaxor and ferroelectric phases due to their comparable free energies in the two-phase coexistence region. Moreover, it was also found that the BNST–xLN system processes predominant electrostrictive behaviors with relatively high electrostrictive coefficient (Q33) and excellent temperature stability when the field-induced phase transition cannot be trigged by the applied electric field, as evidenced by a fact that the Q33 value of BNST–0.08LN ceramic keeps almost constant as high as ~ 0.028 m4/C2 in the temperature range from room temperature to 120 °C.

Piezoelectric ceramics xLiNbO3–yBiScO3–(1−x−y)PbTiO3 (LN–BS–PT, 0.00 ≤ x ≤ 0.10, 0.30 ≤ y ≤ 0.36) were synthesized and their phase diagram and morphotropic phase boundary between rhombohedral and tetragonal phases have been confirmed. The optimal properties were found at the composition of 0.03LN–0.36BS–0.61PT with piezoelectric coefficient d33* value of 702 pm/V, d33 of 551 pC/N, planar electromechanical coupling factor kp of 0.51, remnant polarization Pr of 46.5 µC/cm2, Curie temperature Tc of 337 °C, and a large strain of 0.351% at an electric field of 50 kV/cm and frequency of 2 Hz with a low strain hysteresis of 5.9%. The Curie temperature of the ternary system presents a linear relationship with LiNbO3 and BiScO3 contents. The optimization of these electric properties was probably ascribed to the enhancement in domain walls and the improving mobility of domain switching due to LiNbO3 doping.

A x BiScO 3 –(1- x - y )PbZrO 3 – y PbTiO 3 (denoted as x BS–(1- x - y )PZ– y PT) ternary piezoelectric system was prepared by combining BiScO 3 –PbTiO 3 and PbZrO 3 –PbTiO 3 for high-temperature applications. The morphotropic phase boundary region of the ternary system was identified by X-ray diffraction results together with piezoelectric and dielectric performance, which located at x = 0.054, y = 0.470; x = 0.072, y = 0.479; and x = 0.108, y = 0.492 composition intervals. Among all samples prepared, 0.072BS–0.449PZ–0.479PT displays the optimal piezoelectric and dielectric properties – piezoelectric coefficient d 33 of 426 pC/N, relative dielectric constant e r of 1703, electromechanical coupling factor k p of 0.55, and Curie temperature T c of 317 °C. Additionally, this composition exhibits excellent thermal stability over a broad temperature range. Within the temperature range of 40–200 °C (0.63 T c ), variations in k p , mechanical quality factor Q m , and e r are 16.7% (Δ k p / k p ), 14.8% (Δ Q m / Q m ), and 5.22/°C ( ∂ e / ∂ T ), respectively. The improved piezoelectric, dielectric properties and thermal stability is possibly attributed to the increasing number of irreversible non–180° domains that formed upon addition of BiScO 3 .

Lead-free 0.985[(0.94-x)Bi0.5Na0.5TiO3–0.06BaTiO3–xSrTiO3]–0.015LiNbO3 [(BNT–BT–xST)–LN, x = 0–0.05] piezoelectric ceramics were prepared by using a conventional solid-state reaction method. It was found that the long-range ferroelectric order in the unmodified (BNT–BT)–LN ceramic was disrupted and transformed into the ergodic relaxor phase with the ST substitution, which was well demonstrated by the dramatic decrease in remnant polarization (Pr), coercive field (Ec), negative strain (Sneg) and piezoelectric coefficient (d33). However, the degradation of the ferroelectric and piezoelectric properties was accompanied by a significant increase in the usable strain response. The critical composition (BNT–BT–0.03ST)–LN exhibited a maximum unipolar strain of ~0.44% and corresponding normalized strain, Smax/Emax of ~880 pm/V under a moderate field of 50 kV/cm at room temperature. This giant strain was associated with the coexistence of the ferroelectric and ergodic relaxor phases, which should be mainly attributed to the reversible electric-field-induced transition between the ergodic relaxor and ferroelectric phases. Furthermore, the large field-induced strain showed relatively good temperature stability; the Smax/Emax was as high as ~490 pm/V even at 120 °C. These findings indicated that the (BNT–BT–xST)–LN system would be a suitable environmental-friendly candidate for actuator applications. This article is protected by copyright. All rights reserved.

Lead-free (1−x)(0.0852Bi0.5Na0.5TiO3–0.12Bi0.5K0.5TiO3–0.028BaTiO3)–xCaZrO3 piezoelectric ceramics (BNT−BKT−BT−xCZ, x=0, 0.01, 0.02, 0.03, 0.04 and 0.05) were prepared by using a conventional solid-state reaction method. The effects of CZ-doping on the structural, dielectric, ferroelectric and piezoelectric properties of the BNT−BKT−BT−xCZ system were systematically investigated. The polarization and strain behaviors indicated that the long-range ferroelectric order in the unmodified BNT−BKT−BT ceramics was disrupted by the increase of CZ-doping content, and correspondingly the depolarization temperature (Td) shifted down from 109 °C to below room temperature. When x>0.03, accompanied with the drastic decrease in the remnant polarization (Pr) and piezoelectric coefficient (d33), the electric-field-induced strain was enhanced significantly. A large unipolar strain of 0.35% under an applied electric field of 70 kV/cm (Smax/Emax=500 pm/V) was obtained in the BNT−BKT−BT−0.04CZ ceramics at room temperature, which was attributed to the reversible electric-field-induced phase transition between the relaxor and ferroelectric phases.

High-quality (001) oriented epitaxial 0.9BiFeO3–0.1TbMnO3 thin films were grown on La2/3Sr1/3MnO3 and SrRuO3 buffered SrTiO3 substrate using pulsed laser deposition. X-ray diffraction showed that the films are single-phase perovskite without secondary impurity phases. Domain structures and upward ferroelectric self-poling phenomenon were distinctly observed in both films with compressive epitaxial strains. Furthermore, the upward self-poling disappears in polycrystalline 0.9BiFeO3–0.1TbMnO3 thin film on Pt/TiO2/SiO2/Si substrates. Through local switching spectroscopy measurements, the evidence of enhanced ferroelectric switching and piezoelectric response characteristics have been provided.

BaTiO 3 (BT) template with (100) orientations (f ≈ 98%) was synthesized by molten salt and topological chemical microcrystal conversion method. The templated grain growth technique was then used to prepare highly textured 0.675Pb(Mg 1/3 Nb 2/3 )0 3 -0.325PbTiO 3 (PMN-PT) ceramics. The effects of BaTiO3 templates on the microstructure and properties of textured ceramics have been investigated. It is found that BT template is beneficial to the (100) texture and also the properties of PMN-PT ceramics. The Lotgering factors, which describe the texture of PMN-PT ceramics, increase with the additions of BaTi03 template. Highly oriented PMN-PT ceramic with Lotgering factor f up to 66% was obtained at 6 wt% BT template content. The hysteresis loops show the coercive electric field is nearly independent on the template concentration. The piezoelectric properties of PMN-PT ceramics are closely relative to their textures. A large strain of 0.35% under 50kV/cm electric-field intensity is observed for the ceramic with Lotgering factor f of 66%, which is 1.54 times as that of the random-orientated ceramic in the same field. The corresponding low-field coefficients d∗ 33 is up to 1046 pm/V (E< 10 kV/cm), which is 2.3 times as that of the sample with random crystal orientations.

Piezoelectric ceramics with large energy density coefficient d33·g33 value have been found suitable for piezoelectric energy harvesting applications. In this study, the phase structures and piezoelectric properties of xPb(Zr0.5Ti0.5)O3−yPb(Zn1/3Nb2/3)O3−(1−x−y)Pb(Ni1/3Nb2/3)O3 (xPZT−yPZN−(1−x−y)PNN) ceramic were investigated with systematically varying PZN and PNN components. The ternary phase diagram of PZT−PZN−PNN system was illustrated and the composition region of morphotropic phase boundary (MPB) was determined. Piezoelectric and dielectric measurements verify that the materials in MPB region all present large d33 and d33·g33 values. In particular, very high d33·g33 coefficients of 20162.2 × 10−15 m2/N and 21026.3 × 10−15 m2/N are observed from samples 0.75PZT−0.15PZN−0.1PNN and 0.8PZT−0.05PZN−0.15PNN with compositions located on the rhombohedral phase side near MPB because the dielectric coefficient e33T/e0 decreases faster than the d33 coefficient at this side.