Enhanced electrical properties in Nd and Ce co-doped CaBi4Ti4O15 high temperature piezoceramics

Lead-free piezoelectric material with excellent piezoelectric properties and high Curie temperature is necessary for practical applications. In this work, (Nd, Ce) co-doped CaBi₄Ti₄O₁₅ (CBT) ceramics were prepared by the conventional solid-state reaction technique. The effect of (Nd, Ce) co-doping on the structure and resulting electrical properties of CBT ceramics was systematically investigated. The optimized comprehensive performances were obtained at x?=?0.075 with a large piezoelectric coefficient (19 pC/N), a low dielectric loss (0.073%) and a high Curie temperature (794?°C). More importantly, the ceramic also maintained a very high resistance and a low dielectric loss even at 400?°C (ρ?=?2.5?×?10⁸ Ω?cm, tan δ?=?1.96%) and the d₃₃ showed no sign of waning after annealed at 400?°C, which shows great potential for high temperature piezoelectric device applications. Related mechanisms for the enhancement of electrical properties were discussed.     

Enhanced piezoelectric properties and temperature stability of Bi4Ti3O12-based Aurivillius ceramics via W/Nb substitution

Bi₄Ti₃O₁₂ (BIT), a typical Aurivillius ceramics with high Curie temperature (T_c ? 675 °C), has great potential for high temperature applications. This work provides an effective method of inducing structure distortion, relieving the tetragonal strain of the TiO₆ octahedron and decreasing the concentration of oxygen vacancies to improve the piezoelectricity and temperature stability of BIT ceramics. Bi₄Ti_2.98W_0.01Nb_0.01O₁₂ possesses an optimum piezoelectric coefficient (d₃₃) of 32 pC/N, a high T_c of 655 °C and a large resistivity of 3 × 10⁶ Ω·cm at 500 °C. The maximum d₃₃ reported here is approximately quadruple than that of pure BIT (?7 pC/N). Moreover, the d₃₃ of W/Nb co-doped BIT and the in-situ temperature stability of the compression-mode sensor present a highly stable characteristic in the range of 25–600 °C. These results imply that W/Nb-modified BIT ceramics is a promising candidate for application at high temperatures of up to 600 °C.     

Remarkable piezoelectric activity and high electrical resistivity in Cu/Nb co-doped Bi4Ti3O12 high temperature piezoelectric ceramics

Cu/Nb co-doped Aurivillius type Bi₄Ti_3-x(Cu_1/3Nb_2/3)_xO₁₂ (BTCN) ceramics were investigated as a potential candidate for high temperature piezoelectric application. The microstructure, phase structure and resulting piezoelectric properties and conduction behaviors were systematically investigated. A remarkable d₃₃ of 38 pC/N was achieved in the ceramic with a composition of x = 0.015, which may be ascribed to the enhancement of remanent polarization and decrease of coercive field. Moreover, a high DC resistivity of 8.39 × 10⁶ Ω·cm at 500 °C was also obtained in the composition, due to the decrease of the oxygen vacancy concentration induced by the doped Cu/Nb. Furthermore, the ceramic also exhibited stable thermal annealing behaviors and excellent fatigue resistance. All the results demonstrated the great potential of the Cu/Nb co-doped Bi₄Ti₃O₁₂ ceramics for high temperature piezoelectric applications.     

Temperature-driven phase transitions and enhanced piezoelectric responses in Ba(Ti0.92Sn0.08)O3 lead-free ceramic

Ferroelectric phases coexistence or transition is an important strategy on generating high piezoelectricity. Here, the temperature-induced phase structural evolution correlated with small signal piezoelectric response d₃₃, bias-field piezoelectric activity d^max₃₃(E), unipolar and bipolar strain piezoelectric outputs d^*₃₃ in Ba(Ti_0.92Sn_0.08)O₃ (BTS0.08) ceramic was investigated in details. Temperature-driven successive phase transitions from rhombohedral (R) to orthorhombic (O), tetragonal (T), finally to cubic (C) phases took place around 14?°C, 38?°C and 61?°C, respectively. The highest d₃₃ value of 675 pC/N is achieved in the T-C phase transition. However, the O-T phase boundary gives the highest d^max₃₃ =?1170?p.m./V, bipolar d^*₃₃ =?822?pm/V and unipolar d^*₃₃ =?1318?pm/V. The temperature-driven phase transition exhibits large enhancements in piezoelectric property comparable to that of composition-induced phase boundary. These features suggest an effective method to design high-performance piezoelectrics by tailoring the types of phase boundary.     

Achievement of high electric performances for bismuth titanate-based piezoceramics via hot press sintering

Bi₄Ti₃O₁₂ (BIT) ceramic has great potential in high-temperature environment due to its high Curie temperature T_C ~ 675 °C. In this work, hot press sintering (HPS) is applied on the 0.01 mol Ce and Nb/Cr co-doped BIT (BCTNC) ceramics to enhancing the low piezoelectric coefficient (d₃₃ < 7 pC/N) and resistivity. Extremely high d₃₃ (~39 pC/N) together with high T_C (~672 °C) and high dc resistivity ρ (~1.49 ×10⁷ Ω?cm at 500 °C) are obtained in HPS samples. The enhancement of piezoelectricity benefits from high density of domain and high poling electric field. Moreover, outstanding thermal stability of piezoelectric constant (d₃₃ ~ 35 pC/N after annealing at 650 °C) and low dielectric loss (tanδ ~ 3.8% at 500 °C) are observed as well. These findings are instrumental in understanding HPS and provide a possible manipulation of crystallized mechanism and domains growing kinetics to enhance piezoelectric performances of BIT based ceramics.     

Enhanced electrical properties in W/Cu co-doped CaBi2Nb2O9 high-temperature piezoelectric ceramics

CaBi₂Nb₂O₉ (CBN)-based high-temperature piezoelectric ceramics with the formula of CaBi₂Nb_2−x(W_3/4Cu_1/4)_xO₉ were prepared via the traditional solid-state reaction method. Both the bulk microstructure and the electrical performance of the W/Cu co-doped CBN-based ceramics were systematically investigated. The results indicated that the W/Cu incorporation into the Nb-site altered the crystal structure, which enhanced the piezoelectricity and resistivity. The ceramic with the composition CaBi₂Nb_1.96(W_3/4Cu_1/4)_0.04O₉ exhibited good performance with a high d₃₃ (~14 pC/N) and T_C (~939℃). Moreover, the ceramic exhibited a good electrical resistivity (ρ) of 4.91 × 10⁵ Ω·cm and a low dielectric loss (tanδ) of 0.1 at 600℃. Furthermore, the ceramic that was annealed at 900℃ for 2 h presented a d₃₃ value of 13 pC/N, thus indicating good thermal stability of the piezoelectric properties. All these results confirm that the CaBi₂Nb_1.96(W_3/4Cu_1/4)_0.04O₉ ceramic may act as a potential promising candidate for piezoelectric device applications in high-temperature environments.     

Influence of Co/W co-doping on structural and electrical properties of Na0.5Bi2.5Nb2O9 piezoelectric ceramics

Co/W co-doped Na_0.5Bi_2.5Nb_2-x(Co_1/3W_2/3)_xO₉ (NBNCW-x) ceramic samples were prepared by the conventional solid state reaction method. The electrical properties and crystal structure of the NBNCW-x ceramic samples were analyzed in detail. The XRD and Rietveld refinement results showed that the samples lattice distortion decreased with the increment of Co/W doping. The XPS results showed that the number of oxygen vacancies in the Na_0.5Bi_2.5Nb₂O₉ ceramics could be reduced by the substitution of a small amount of Co/W. The weakened lattice distortion and reduced number of oxygen vacancies of the Na_0.5Bi_2.5Nb₂O₉ ceramics synergistically contributed to its improved electrical properties. In particular, the Na_0.5Bi_2.5Nb_1.97(Co_1/3W_2/3)_0.03O₉ ceramic exhibited the best performance, and its T_c, d₃₃ and P_r were 780 °C, 24.9 pC/N and 12.6 μC/cm², respectively. The dielectric loss was only 3.3% at 550 °C. In addition, this ceramic exhibited excellent thermal stability, with the d₃₃ value of the ceramic being 95.2% of its original value when annealed at 750 °C. These properties indicate that the Co/W co-doped Na_0.5Bi_2.5Nb₂O₉-based ceramics have potential application in the high-temperature field.     

Fabrication and piezoelectric properties of BaTiO3/BaTiO3-Bi(Mg1/2Ti1/2)O3-BiFeO3 composites

We fabricated xBaTiO₃ (BT)/(1-x)[BaTiO₃-Bi(Mg_1/2Ti_1/2)O₃-BiFeO₃] (BT-BMT-BF)?+?0.1?wt%MnCO₃ composites by spark plasma sintering and investigated the effect of BT content x, BT powder size, and BT-BMT-BF composition on piezoelectric properties. For xBT/(1-x)(0.3BT-0.1BMT-0.6BF) +?0.1?wt%MnCO₃ (x?=?0–0.75) composites with a 0.5-µm BT powder, the dielectric constant was increased with x, and the relative density was decreased at x?=?0.67 and 0.75, creating optimum BT content of x?=?0.50 with a piezoelectric constant d₃₃ of 107?pC/N. When a larger 1.5-µm BT powder was utilized for the composite with x?=?0.50, the d₃₃ value increased to 150?pC/N due to the grain size effect of the BT grains. To compensate for a compositional change from the optimum 0.3BT-0.1BMT-0.6BF due to partial diffusion between the BT and 0.3BT-0.1BMT-0.6BF grains, a 0.5BT/0.5(0.275BT-0.1BMT-0.625BF)?+?0.1?wt%MnCO₃ composite with the 1.5-µm BT powder was fabricated. We obtained an increased d₃₃ value of 166?pC/N. These results provided a useful composite design to enhance the piezoelectric properties.     

Pairing high piezoelectric properties and enhanced thermal stability in grain-oriented BNT-based lead-free piezoceramics

(Bi_0.5Na_0.5)TiO₃ (BNT)-based piezoceramics usually exhibit enhanced piezoelectric coefficient d₃₃ together with the deterioration of depolarization temperature T_d, which is the common drawback limiting their use in practical application. Here, we demonstrate that harnessing the microstructure in BNT-based ceramics will be an efficient way to resolve this obstacle. <00l> oriented piezoelectric ceramics 0.94(Bi_0.5Na_0.5)TiO₃ ?0.06BaTiO₃ was engineered by templated grain growth (TGG) using NaNbO₃ (NN) as templates. The manufactured textured ceramics with the optimized microstructure was characterized by not only approximately 200% enhancement in the magnitude of piezoelectric response (d₃₃~297pC/N) but also improved thermal stability (T_d~57?°C) in comparison to its randomly oriented counterparts (d₃₃~151pC/N and T_d~32?°C). Moreover, the enhanced piezoelectricity in grain oriented specimens primarily originated from a high degree of non-180° domain switching as compared to the randomly axed ones. The current study opens the door to pair high piezoelectric properties and enhanced thermal stability in BNT-related materials though texture technique.     

Enhanced electrical properties of Cr2O3 addition NBT-based high-temperature piezoelectric ceramics

Owing to industrial and technological developments, there has been an increasing demand for piezoelectric ceramics that can function at temperatures of 500°C or higher. Na_0.5Bi_4.5Ti₄O₁₅ (NBT) with its high Curie temperature (T_C) of 650°C is a typical bismuth layer–structured ferroelectric. However, its relatively low piezoelectric coefficient (d₃₃ ∼ 16 pC/N) hinders its potential application at high temperatures. In this study, compositions of Ca_0.05(Na_0.5Bi_0.5)_0.95Bi₄Ti₄O₁₅ with different additions of Cr₂O₃ (CNBT–Cr100x) were designed based on previous studies on Ca²⁺-doped NBT piezoceramics, and the effects of the addition on the structural and electrical properties were investigated. The d₃₃ value of CNBT–Cr20 was as high as 29 pC/N, almost twice higher than that of pure NBT ceramics. This increase was investigated in depth using X-ray diffraction refinement and piezoelectric force microscopy in terms of intrinsic and extrinsic contributions. The P_s values of CNBT and CNBT–Cr20 were almost equal. The density of the domain walls of CNBT–Cr20 was significantly higher than that of CNBT, indicating that the increase of d₃₃ of CNBT–Cr20 is mainly due to the increase in the extrinsic contribution. The CNBT–Cr20 ceramic exhibited excellent properties with a high T_C of 655°C, a high d₃₃ of 29 pC/N, and a resistivity high than 10⁶ Ω cm at 500°C, demonstrating its potential for applications at high temperatures such as 500°C.     

Reduced dielectric loss and high piezoelectric constant in Ce and Mn co-doped BiScO3-PbCexTi1-xO3-Bi(Zn0.5Ti0.5)O3 ceramics

MnO₂-doped 0.99(0.36BiScO₃-0.64PbTi_1-xCe_xO₃)-0.01Bi(Zn_0.5Ti_0.5)O₃ (BS-PTC-BZT-MnO₂) ceramics are fabricated by the solid-state method. Here, it's firstly reported that Ce element can reduce dielectric loss (tan δ) and suppress the decrease of piezoelectric constant (d₃₃) simultaneously. Effects of Ce contents on the structure and electrical properties of BS-PTC-BZT-MnO₂ ceramics are studied. The ceramics (x?=?0.02) with MPB (rhombohedral-tetragonal) possess low dielectric loss (tan δ?=?1.36%, 1?kHz) and high piezoelectric constant (d₃₃ =?360 pC/N) simultaneously, which is superior to most reported BS-PT. Besides, excellent comprehensive properties including high Curie temperature (T_C =?422?°C), large dielectric constant (?_r =?1324), and high remnant polarization (P_r =?35.1?µC/cm²) are obtained. Asymmetric S-E and P-E hysteresis loops indicate that defects and oxygen vacancies are induced by multi-valence elements (Ce and Mn), which is the origin for reducing tan δ. In addition, good thermal stability of piezoelectric and dielectric properties is observed. These results indicate that Ce and Mn co-doped BS-PTC-BZT-MnO₂ ceramics can be well applied as power electronic devices under high temperature.     

Composite microstructures and piezoelectric properties in tantalum substituted lead-free K0.5Na0.5Nb1-xTaxO3 ceramics

K_0.5Na_0.5Nb_1-xTa_xO₃ (KNNT) (with x?=?0.00, 0.05, 0.10, 0.20, 0.30, 0.50 and 1) ceramics are prepared by ball milling and two calcinations at 830?°C for 5?h. Subsequent sintering of centimeter size pellets, 1–2?mm thick, is studied using conventional and spark plasma sintering techniques with various conditions. X-Ray diffraction and Raman spectroscopy phase identification reveal orthorhombic to tetragonal phase transitions occurring at about x?=?0.50, associated to chemical disorder. Scanning electron microscope observations and associated energy dispersive X-ray spectroscopy analysis reveal some composite aspect of the ceramics. Substitution of niobium by tantalum, corresponding to x increase, decreases significantly the grain size but also the densification of the ceramics sintered by conventional sintering, while, enhancement of the piezoelectric properties is observed for both sintering techniques. Thanks to parameters optimization of the spark plasma sintering process, temperature-time-pressure, significant improvement of the relative density over 96%, is obtained for all the compositions sintered between 920 and 960?°C, under 50?MPa, for 5–10?min with heating rates of 100?°C/min. High relative permittivity (ε_r =?1027), piezoelectric charge coefficient (d₃₃ =?160 pC/N) and piezoelectric coupling factor (k_p =?46%) are obtained in spark plasma sintered K_0.5Na_0.5Nb_1-xTa_xO₃ composite ceramics, for x ranging between 0.10 and 0.30 and for some specific spark plasma sintering conditions. Thus, tantalum single element substitution on niobium site, combined with spark plasma sintering, is revealed to be a powerful combination for the optimization and the reliability of piezoelectric properties in KNN system.     

Synchronous improvement of piezoelectric property and temperature stability in PSN-PMN-PT ceramics by forming composites with ZnO

Relaxor ferroelectric materials with high piezoelectric properties always suffer from low phase transition temperature, making them difficult to satisfy the demands for high-temperature environment applications. In this work, we proposed a composite approach to improve the piezoelectricity and temperature stability of PSN-PMN-PT ceramics at the same time. The ZnO nanoparticles as a second phase were introduced into the PSN-PMN-PT matrix to form composite ceramics. When the ZnO content reaches 5 mol%, the piezoelectric constant d₃₃ increases from 529 pC/N for pure PSN-PMN-PT ceramic to 590 pC/N. Meanwhile, the retained d₃₃ after annealing at 200 °C keeps 92% of the value before annealing, indicating the thermal depolarization behavior is suppressed by the composite method. The synchronous improvement of the d₃₃ and thermal depolarization behavior for PSN-PMN-PT/ZnO composite ceramics is related to the local electric field and stress field caused by the addition of ZnO particles. Our results pave a simple and effective way to develop next-generation PT-based relaxor ferroelectric ceramics.     

Comparison of multi-valent manganese oxides (Mn4+, Mn3+, and Mn2+) doping in BiFeO3-BaTiO3 piezoelectric ceramics

Different manganese oxides-doping effects were compared in piezoceramic BiFeO₃-BaTiO₃ system. 0.67Bi_1.05(Fe_0.99Mn^x_0.01)O₃-0.33BaTiO₃ (valence state x = 4+, 3+, and 2+) ceramics were prepared via a solid-state reaction process followed by furnace-cooling (FC) or water-quenching (WQ) process. For the FC ceramics, the direct piezoelectric sensor coefficient (d₃₃) was almost independent of valence state of doped Mn, while d₃₃ depended on the fraction of Fe³⁺/Fe²⁺ in WQ ceramics. The d₃₃ value was highest for the donor Mn⁴⁺-doped ceramic, among the FC ceramics, with 175 pC/N. However, acceptor-doping with Mn²⁺ prevented the transition of Fe ion valence state from 3+ to 2+ in the WQ ceramics, the Mn²⁺-doped WQ ceramic showed the largest d₃₃ of 313 pC/N and converse piezoelectric actuator coefficient, d₃₃^* of 352 pm/V, with high Curie phase transition temperature (482 °C).     

Enhanced piezoelectric,electrocaloric and energy storage properties at high temperature in lead-free Bi0.5(Na1-xKx)0.5TiO3 ceramics

The piezoelectric, electrocaloric and energy storage properties were systemically investigated in lead-free Bi_0.5(Na_1-xK_x)_0.5TiO₃ ceramics from room temperature to high temperature region. These ceramics can be poled completely to obtain large piezoelectric coefficient (104–153 pC/N) at low electric field of ~30?kV/cm. The piezoelectric property shows good thermal stability due to high depolarization temperature (T_d). For BNKT₂₀, a large low electric field-induced strain of 0.36% is obtained at 120?°C under 50?kV/cm, the corresponding normalized strain coefficient is up to 720?pm/V, which is larger than other BNT-based ceramics at high temperature region. The electrocaloric properties of these ceramics are studied via indirect and direct methods. Large EC value (~1.08?K) in BNKT₂₀ ceramic is obtained at 50?kV/cm using indirect calculation. Above 100?°C, the dielectric energy storage density and efficiency of BNKT₂₀ is still up to ~0.85?J/cm³ and 0.75, respectively. The BNKT_x ceramics may become promising candidates in the fields of actuators, electrocaloric cooling and energy storage at high temperature region.     

Na0.5Bi2.5Nb2O9 lead-free piezoelectric ceramics with high Curie temperature derived from sol–gel route

An Aurivillius phase bismuth layer-structured compound, Na_0.5Bi_2.5Nb₂O₉ (NBN), has been prepared by an economical aqueous sol–gel technique. The results indicated that pure NBN nano-particles can be obtained at a low temperature of 650°C and the morphology are platelike with grain sizes of about 40?nm. Using these nano-particles, the dense NBN ceramics were fabricated at 1100°C for 2?h. The Curie temperature T_c and piezoelectric coefficient d₃₃ at room temperature for the present ceramic were found to be 770°C and 11?pC/N, respectively. Thermal annealing studies indicate that the NBN ceramic possesses stable piezoelectric properties, demonstrating it is a promising candidate for high-temperature applications.     

Performance enhancement of soft-PZT5 piezoelectric ceramics using poling technique

Pb(Zr_1−xTi_x)O₃ (PZT) ceramics are the most widely used piezoelectric ceramics due to their excellent performance. It has been reported that the direct current poling (DCP) apply on alternating current poling (ACP) relaxor-PbTiO₃ ferroelectric crystals can further improve the piezoelectric properties. Herein, we report the dielectric and piezoelectric properties of soft-PZT5 ceramics under DCP, ACP, and ACP + DCP methods. The piezoelectric coefficient d₃₃ of the soft-PZT5 ceramics was 560 pC/N using ACP+DCP at room temperature (RT), which is 4% higher than the ACP-treated sample (540 pC/N) and 24% higher than the DCP-treated sample (450 pC/N). The ideal poling temperatures of DCP and ACP were found to be 120°C and 60°C, showing optimal d₃₃ values of 540 pC/N and 565 pC/N, respectively. The ACP and ACP+DCP samples show the same aging trend. After 30 days of aging, the d₃₃ values of the DCP, ACP, and ACP+DCP soft-PZT5 ceramics were 415 pC/N, 500 pC/N, and 510 pC/N, respectively, showing decreases of 12%, 8%, and 9%, respectively. This work indicates that the ACP+DCP method is an effective method to improve the piezoelectric properties of soft-PZT5 ceramics.     

SnO2 modified PNN-PZT ceramics with ultra-high piezoelectric and dielectric properties

In this work, a two-step solid-state reaction method is used to prepare the 0.55 Pb(Ni_1/3Nb_2/3)O₃-0.135PbZrO₃-0.315PbTiO₃/xSnO₂ (PNN-PZT/xSnO₂) ceramics. The influences of SnO₂ on the crystalline structure, electromechanical properties, and temperature stability of PNN-PZT ceramics were studied in detail. The results demonstrate that the Sn⁴⁺ ions are successfully introduced into the PNN-PZT crystalline lattice and substitute B-site Ni²⁺ and Zr⁴⁺. The x = 0.0025 ceramic with the coexistence of rhombohedral, tetragonal, and pseudocubic phases exhibits the optimized comprehensive properties: the quasi-static piezoelectric constant d₃₃, large-signal d₃₃*, electromechanical coupling coefficients k_p and k_t, free dielectric constant ε_r, and mechanical quality factor Q_m are 1123 pC/N, 1250 p.m./V, 0.63, 0.54, 9529, and 57, respectively. Meanwhile, the Curie temperature for this composition is 103 °C, almost maintaining the same level as the PNN-PZT matrix. After annealing at 75 °C, the retained d₃₃ of x = 0.0025 ceramic is as high as 975 pC/N, superior to the PNN-PZT matrix (retained d₃₃ ≈ 873 pC/N). Our results provide a promising piezoelectric material for board bandwidth, high sensitivity, and miniaturized medical ultrasonic transducers applications.     

Structural and piezoelectric properties of <001> textured PZT‐PZNN piezoelectric ceramics

Rhombohedral 0.69Pb(Zr_0.47Ti_0.53)‐0.31Pb(Zn_0.6Ni_0.4)NbO₃ (PZT‐PZNN) ceramics were textured using 10.0 vol. % BaTiO₃ (BT) platelets along the <001> direction at 950°C with a high Lotgering factor of 95.3%. BT platelets did not react with the PZT‐PZNN ceramics, and the textured PZT‐PZNN ceramic had a tetragonal structure. The PZT‐PZNN ceramics exhibited a strain of 0.174% with a piezoelectric strain constant (d*₃₃) of 580 pC/N at 3.0 kV/mm. The textured PZT‐PZNN ceramic showed an increased strain of 0.276% and d*₃₃ of 920 pC/N at 3.0 kV/mm, which can be explained by the domain rotation. However, the d₃₃ values of the textured specimens are smaller than those of the untextured specimens because of the small remanent polarization and relative dielectric constant of BT platelets. The textured PZT‐PZNN ceramic synthesized in this work can be used for piezoelectric multilayer actuators because of its large strain and low sintering temperature.     

Enhanced piezoelectric and ferroelectric properties of BiFeO3-BaTiO3 lead-free ceramics by optimizing the sintering temperature and dwell time

0.7BiFeO₃-0.3BaTiO₃ (BFO-0.3BT) ceramics were prepared to uncover the impacts of sintering temperature (T_S) and dwell time (t_d) on the microstructure and electrical properties. With increasing the T_S or t_d, the grain sizes increase along with the porosity decreases, which is in favor of the alignment of dipole. However, excess T_S or t_d are inclined to cause the volatilization of Bi₂O₃, which deteriorates piezoelectric properties. Because of the R-T two-phase coexistence, low defect ions concentration and porosity, as well as appropriate grain size, the excellent d₃₃?=?208?pC/N and k_p?=?35.46% as well as P_r?=?28.52?μC/cm² were achieved in BFO-0.3BT ceramics at T_S?=?1000?°C and t_d?=?6?h. In addition,large unipolar strain 0.13% and d₃₃*?=?256.2?pm/V also were obtained in BFO-0.3BT ceramics at T_S?=?1000?°C and t_d?=?6?h. This research indicates that the porosity and defect ion concentration as well as grain size also play an important role in piezoelectric properties in BFO-BT ceramics.