Study of sintering behavior of PAN–PZT using dilatometry and co-relation with piezoelectric properties

The sintering behavior of Pb(Al_0.5Nb_0.5)O₃–Pb(Zr_0.52Ti_0.48)O₃ (PAN–PZT) ceramics was investigated. The sintering process of PAN–PZT was divided into four stages based on the amount of in-situ linear shrinkage: (Stage 1) initial stage at sintering temperature RT≤T_s≤ to 770 °C, (Stage 2) perovskite formation stage at 770≤T_s≤990 °C, (Stage 3) densification stage at 990≤T_s≤1265 °C and (Stage 4) Pb-loss stage at T_s>1265 °C. During stage 1, heating of PAN–PZT compact did not cause structural changes except the thermal expansion. During stage 2, the PZT-perovskite structure was formed by rearrangement of crystals. During stage 3, the specimen was rapidly densified with two peaks of strain rate. During stage 4, Pb was volatilized and this loss resulted in sudden increase of shrinkage. On analyzing the sintering stages, the optimized sintering conditions were considered as 1250 °C just before of Pb-loss stage. The effects of T_s on the crystal structure, microstructure and the piezoelectric performance were analyzed and documented.     

Dielectric,ferroelectric and field-induced strain behavior of K0.5Na0.5NbO3-modified Bi0.5(Na0.78K0.22)0.5TiO3 lead-free ceramics

Lead-free piezoelectric (1 ? x)Bi_0.5(Na_0.78K_0.22)_0.5TiO₃–xK_0.5Na_0.5NbO₃ (BNKT–xKNN, x = 0–0.10) ceramics were synthesized using a conventional, solid-state reaction method. The effect of KNN addition on BNKT ceramics was investigated through X-ray diffraction (XRD), dielectric, ferroelectric and electric field-induced strain characterizations. XRD revealed a pure perovskite phase with tetragonal symmetry in the studied composition range. As the KNN content increased, the depolarization temperature (T_d) as well as maximum dielectric constant (?_m) decreased. The addition of KNN destabilized the ferroelectric order of BNKT ceramics exhibiting a pinched-type hysteresis loop with low remnant polarization (11 μC/cm²) and small piezoelectric constant (27 pC/N) at 3 mol% KNN. As a result, at x = 0.03 a significant enhancement of 0.22% was observed in the electric field-induced strain, which corresponds to a normalized strain (S_max/E_max) of ～434 pm/V. This enhancement is attributed to the coexistence of ferroelectric and non-polar phases at room temperature.     

Densification behavior and electrical properties of CuO-doped Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ternary ceramics

CuO modified Pb(In_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PIN–PMN–PT) ternary relaxor based ferroelectrics with the composition near the morphotropic phase boundary were synthesized by two-step columbite precursor method. The introduction of CuO significantly improved the sinterability of PIN–PMN–PT ceramics, resulting in the full densification of samples at lower sintering temperatures. It also profoundly modified the crystal structure and fracture mode of the ceramics. Properly increasing CuO content led to the disappearance of rhombohedral-tetragonal phase transition, remarkably improved the Curie temperature (T_c), and made the ceramics more relaxorlike. The ternary ceramics doped with 0.25 wt% CuO possessed optimum piezoelectric properties (d₃₃=584 pC/N, d₃₃^*=948 pC/N, and k_p=0.68), high ferroelectric properties (E_c=9.9 kV/cm, and P_r=33.1 μC/cm²), low dielectric loss (tan δ=0.9%), and wider temperature usage range (T_c=225 °C). The obtained properties are much higher than those of previously reported PIN–PMN–PT based ceramics, indicating that CuO doped PIN–PMN–PT is a promising candidate for electromechanical applications with high performance and wide temperature/electric field usage ranges.     

Dielectric,ferroelectric and field-induced strain response of lead-free (Fe,Sb)-modified (Bi0.5Na0.5)0.935Ba0.065TiO3 ceramics

Lead-free piezoelectric ceramics (Bi_0.5Na_0.5)_0.935Ba_0.065Ti_1−x(Fe_0.5Sb_0.5)_xO₃ (BNBT6.5–xFS, x=0.005, 0.010, 0.015, 0.020) were prepared by a conventional solid sintering technique. The effects of B-site doping of (Fe, Sb) on the phase structure, microstructure, dielectric, ferroelectric, and piezoelectric properties of BNBT6.5 ceramics were systematically investigated. Results showed that (Fe, Sb) can completely diffuse in the BNBT6.5 lattice in the all studied components. The addition of (Fe, Sb) destroyed the ferroelectric long-range order, and thus promoted the electric field induced strain response. The maximum electric field-induced strain (S_max=0.37%) with normalized strain (d₃₃*=S_max/E_max=454 pm/V) at an applied electric field of 80 kV/cm was obtained at x=0.015. Temperature dependent measurements of both polarization and strain from room temperature to 120 °C suggested that the origin of the large strain is due to a reversible field-induced ergodic relaxor to ferroelectric phase transformation.     

Microwave dielectric properties and low-temperature sintering of Ba3Ti4Nb4O21 ceramics with B2O3 and CuO additions

The low sintering temperature and the good dielectric properties such as high dielectric constant (ɛ_r), high quality factor (Q × f) and small temperature coefficient of resonant frequency (τ_f) are required for the application of chip passive components in the wireless communication technologies. In the present study, the sintering behaviors and dielectric properties of Ba₃Ti₄Nb₄O₂₁ ceramics were investigated as a function of B₂O₃–CuO content. Ba₃Ti₄Nb₄O₂₁ ceramics with B₂O₃ or CuO addition could be sintered above 1100 °C. However, the additions of both B₂O₃ and CuO successfully reduced the sintering temperature of Ba₃Ti₄Nb₄O₂₁ ceramics from 1350 to 900 °C without detriment to the microwave dielectric properties. From the X-ray diffraction (XRD) studies, the sintering behaviors and the microwave dielectric properties of low-fired Ba₃Ti₄Nb₄O₂₁ ceramics were examined and discussed in the formation of the secondary phases. The Ba₃Ti₄Nb₄O₂₁ sample with 1 wt% B₂O₃ and 3 wt% CuO addition, sintered at 900 °C for 2 h, had the good dielectric properties: ɛ_r = 65, Q × f = 16,000 GHz and τ_f = 101 ppm/°C.     

Textured (K0.5Na0.5)NbO3 ceramics prepared by screen-printing multilayer grain growth technique

The screen-printing multilayer grain growth (MLGG) technique is successfully applied to alkaline niobate lead-free piezoelectric ceramics. Highly textured (K_0.5Na_0.5)NbO₃ (KNN) ceramics with 〈0 0 1〉 orientation (f = 93%) were fabricated by MLGG technique with plate-like NaNbO₃ templates. The influence of sintering temperature on grain orientation and microstructure was studied. The textured KNN ceramics showed very high piezoelectric constant d₃₃ = 133 pC/N, and high electromechanical coupling factor k_p = 0.54. These properties were superior to those of conventional randomly oriented ceramics, and reach the level of those of textured KNN ceramic prepared by tape-casting technique. Compared with other grain orientation techniques, screen-printing is a simple, inexpensive and effective method to fabricate grain oriented lead-free piezoelectric ceramics.     

High-power properties of piezoelectric hard materials sintered at low temperature for multilayer ceramic actuators

0.05Pb(Mn_1/3Sb_2/3)O₃–0.05Pb(Al_1/2Nb_1/2)O₃–0.9Pb(Zr_0.48Ti_0.52)O₃ (PMS–PAN–PZT) high power piezoelectric system with both La₂O₃ as a hardener and CuO as a low sintering agent had been synthesized at 900 °C for 2 h. When La₂O₃ doping of the main composition went over 0.5 wt%, the mixed tetragonal and rhombohedral perovskite structure changed to pure rhombohedral perovskite structure. In case of the CuO, 1.0 and 1.5 wt% CuO content significantly improved the sinterability of the PMS–PAN–PZT system processed at 900 °C for 2 h. When La₂O₃ and CuO co-doped in PMS–PAN–PZT ceramics, piezoelectric constants (d₃₃), quality factor (Q_m), electromechanical coupling factor (k_p) and dielectric constant (${\epsilon }_3^{\text{T}}/{\epsilon }_0$) of the piezoelectric ceramics sintered at 900 °C for 2 h were optimized, such as 336 pC/N, 841, 60%, and 1358, respectively. New developed piezoelectric materials are promising for high power multilayer ceramic actuators.     

Processing and enhanced electrical properties of Sr1-x(K0.5Bi0.5)xBi2Nb2O9 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics, Sr_1−x(K_0.5Bi_0.5)_xBi₂Nb₂O₉ (SKBN-x, x=0, 0.2, 0.5, 1.0), were synthesized by a conventional solid-state reaction. Structural and electrical properties of SKBN-x ceramics were investigated. X-ray diffraction analysis suggested that the substitution led to the formation of a layered perovskite structure. Plate-like morphologies for the grains were clearly observed in all the samples, which are characteristic for layer-structure Aurivillius compounds. The Curie temperature (T_c) is found to shift to higher temperature from 445 °C to 509 °C with increasing (K, Bi) content. Excellent remanent polarization (2P_r∼15 μC/cm²) were obtained for SKBN-0.2 ceramic. High piezoelectric coefficient of d₃₃∼21  pC/N were obtained for the samples at x=0.5. Additionally, thermal annealing studies indicated that the piezoelectric coefficient (d₃₃) of SKBN-0.5 was unchanged even if annealing temperature increased to be 450 °C, demonstrating the ceramics are the promising candidates for high-temperature applications.     

Li2O excess (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 lead free piezoelectric ceramics

1 mol% Li₂O excess (Na_0.51K_0.47Li_0.02)(Nb_0.8Ta_0.2)O₃ ceramics were prepared by the conventional mixed oxide method and sintered from 950 to 1200 °C. Also, Li₂O was employed as a sintering aid for high densification and low temperature sintering process. X-ray diffraction results of 1 mol% Li₂O excess (Na_0.51K_0.47Li_0.02)(Nb_0.8Ta_0.2)O₃ lead free piezoelectric ceramics indicated that the specimens were well crystallized and have tetragonal structure. The specimens which sintered at 1050 °C showed the highest piezoelectric properties compared with others. The measured piezoelectric constant and electromechanical coupling coefficient were 231 pC/N and 38.9%, respectively. Curie temperature of (Na_0.51K_0.47Li_0.02)(Nb_0.8Ta_0.2)O₃ ceramics was 344.32, 344.4 and 344.5 °C at 1, 10 and 100 kHz, respectively.     

Microstructure and piezoelectric properties of textured (Na0.84K0.16)0.5Bi0.5TiO3 lead-free ceramics

Textured (Na,K)_0.5Bi_0.5TiO₃ ceramics were fabricated by reactive-templated grain growth in combination with tape casting. The effects of sintering conditions on the grain orientation and the piezoelectric properties of the textured (Na,K)_0.5Bi_0.5TiO₃ ceramics were investigated. The results show that the textured ceramics have microstructure with plated-like grains aligning in the direction parallel to the casting plane. The ceramics exhibit {h 0 0} preferred orientation and the degree of orientation is larger than 0.7. The degree of grain orientation increases with the increasing sintering temperature. The textured ceramics show anisotropy dielectric and piezoelectric properties in the directions of parallel and perpendicular to the casting plane. The ceramics in the perpendicular direction exhibit better dielectric and piezoelectric properties than those of the nontextured ceramics with the same composition. The optimized sintering temperature is 1150 °C where the maximum d₃₃ of 134 pC/N parallel to casting plane, the maximum k₃₁ of 0.31, and the maximum Q_m of 154 in perpendicular direction were obtained.     

Enhanced piezoelectric properties of Aurivillius-type sodium lanthanum bismuth titanate (Na0.5La0.5Bi4Ti4O15) by B-site manganese modification

The Aurivillius-type bismuth layer-structured ferroelectrics (BLSFs) sodium lanthanum bismuth titanate (Na_0.5La_0.5Bi₄Ti₄O₁₅, NLBT) polycrystalline ceramics with 0.0–0.4 wt% MnO₂ were synthesized using conventional solid-state processing. Phase analyses were performed by X-ray powder diffraction (XRPD), and the microstructural morphology was assessed by scanning electron microscopy (SEM). The dielectric and piezoelectric properties of the manganese-modified NLBT ceramics were investigated in detail. The results show that manganese is very effective in promoting the piezoelectric activities of NLBT ceramics, and the reasons for piezoelectric activities enhancement by manganese modification are explained. The NLBT ceramics modified with 0.2 wt% MnO₂ (NLBT-Mn2) possess good piezoelectric properties, with a piezoelectric coefficient d₃₃ of 28 pC/N. This value is the highest value among the modified NLBT-based piezoelectric ceramics examined. The temperature-dependent dielectric spectra show that the Curie temperature T_c of the manganese-modified NLBT ceramics is slightly higher than that of the pure NLBT ceramics. Thermal annealing analysis revealed that the manganese-modified NLBT ceramics possess good thermal stabilities up to 500 °C. These results demonstrate that the manganese-modified NLBT ceramics are promising materials for high temperature piezoelectric applications.     

Microstructure and electrical properties of (Ba0.85Ca0.15)1−xLix(Ti0.90Zr0.10)1−xNbxO3 ceramics with a low dielectric loss and a low sintering temperature

A low sintering temperature is demonstrated for (Ba_0.85Ca_0.15)_1?xLi_x(Ti_0.90Zr_0.10)_1?xNb_xO₃ (BCLTZN-x) piezoelectric ceramics, where BCLTZN-x lead-free piezoelectric ceramics were prepared by the normal sintering. Effects of Li and Nb on the microstructure and electrical properties of these ceramics were investigated. The sintering temperature of BCLTZN-x ceramics was decreased greatly by introducing Li and Nb, and the grain size of these ceramics decreases with increasing x. These ceramics with a small amount of Li and Nb maintain good piezoelectric properties, together with a low sintering temperature and a lower dielectric loss. These ceramics with x = 0.01 demonstrate optimum electrical properties: d₃₃ ～ 353 pC/N, k_p ～ 41.1%, T_c ～ 86 °C, ?_r ～ 4236, and tan δ ～ 0.75%.     

Physical and electrical properties of Nb doped Bi0.5Na0.5[Zr0.59Ti0.41]O3

This research studied the effect of Nb doping on Bi_0.5Na_0.5[Ti_0.41Zr_0.59]O₃ (when Nb concentration = 0.00, 0.01, 0.03, 0.05, 0.07 and 0.09 mol fraction). Nb doped BNTZ ceramics were fabricated using a conventional mixed-oxide method. All samples were calcined at a temperature of 700 °C for 2 h and sintered at a temperature of 900 °C for 2 h. X-ray diffraction patterns suggested that the compounds possessed rhombohedral perovskite structure. SEM micrographs indicated that average grain size decreased as the amount of Nb additives increased. The electrical resistivity showed a decreasing trend with increasing Nb concentration due to excess charge present in the sample. The dielectric constant and dielectric loss of samples showed no particular trend when Nb was added but the optimum was observed when 0.05–0.07 Nb mol fraction was present in BNTZ ceramics. In this study, both microstructure and donor-type effects played an important role in determining electrical resistivity and dielectric properties of these ceramics.     

Effect of CuO addition on magnetic and electrical properties of Sr2Bi4Ti5O18 lead-free ferroelectric ceramics

The effect of CuO addition on magnetic and electrical properties of Sr₂Bi₄Ti₅O₁₈ (SBT) lead-free bismuth layered structure ferroelectric ceramics have been studied and reported. Interestingly, the prepared samples exhibit multiferroic behavior with the coexistence of magnetic and ferroelectric phase transition temperature. Magnetic phase transition with Neel׳s temperature (T_N) of 657 K is observed at 0.75 mol% of CuO added SBT ceramics, which is higher than the well known multiferroic BiFeO₃ (643 K) and the ferroelectric phase transition with Curie temperature (T_C) of 587 K is observed at 1 mol% of CuO added SBT ceramics, which is relatively higher than the reported pure SBT ceramics (558 K). Further, the electrical properties such as dielectric, ferroelectric, piezoelectric, leakage current density characteristics and optical properties were investigated as a function of x (x=0, 0.25, 0.5, 0.75 and 1 mol%). Presence of strong magnetic super-exchange interactions in CuO and the creation of oxygen vacancies play a vital role in the enhancement of magnetic and electrical properties of CuO doped SBT ceramics. Moreover, the present results indicate that, small amount (0.25 mol%) of CuO addition in SBT ceramics enhances the electrical properties significantly and vice versa, large amount (0.75 mol%) of CuO addition enhances the magnetic properties. Thus, the presence of magneto-electric coupling effect was observed in CuO doped Sr₂Bi₄Ti₅O₁₈ ferroelectric ceramics.     

Effects of Li2CO3 and Sm2O3 additives on low-temperature sintering and piezoelectric properties of PZN-PZT ceramics

To assist the development of applications for multilayer piezoelectric devices, the low-temperature sintering piezoelectric ceramics of 0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.49Ti_0.51)O₃ with Li₂CO₃ and Sm₂O₃ additives were fabricated by a conventional solid-state reaction, and their structural and piezoelectric properties were studied. With the addition of Li₂CO₃, the minimum sintering temperature of 0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.49Ti_0.51)O₃ piezoelectric ceramics was reduced from 1125 °C to 950 °C through the formation of a liquid phase and its piezoelectric properties showed almost no degradation. When the sintering temperature was below 950 °C, however, the piezoelectric properties degraded obviously. The additional Sm₂O₃ resulted in a significant improvement in the piezoelectric properties of 0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.49Ti_0.51)O₃ ceramic with added Li₂CO₃. When sintered at 900 °C, the optimized properties of the 0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.49Ti_0.51)O₃ piezoelectric ceramic with 0.3 wt% Li₂CO₃ and 0.3 wt% Sm₂O₃ were obtained as d₃₃ = 483 pC/N, k₃₁ = 0.376, Q_m = 73, ɛ_r = 2524, tan δ = 0.0178.     

Temperature-insensitive dielectric and piezoelectric properties in (1-x)K0.5Na0.5Nb0.997Cu0.0075O3-xSrZrO3 ceramics

Systematic investigation on phase transition, dielectric and piezoelectric properties of (1-x)K_0.5Na_0.5Nb_0.997Cu_0.0075O₃-xSrZrO₃ (x = 0, 0.03, 0.06, 0.09, 0.12, 0.15, abbreviated as KNNC-100xSZ) ceramics was carried out. Due to the coexistence of orthorhombic and tetragonal phase in a wide temperature range, a diffused polymorphic phase transition (PPT) region was achieved in KNNC with x ≥ 0.06. KNNC-12SZ ceramics exhibited high dielectric permittivity (∼1679), low dielectric loss (∼0.02) and small variation (Δe'/ε'_25 °C ≤ 15%) in dielectric permittivity from −78 °C to 237.3 °C. KNNC-6SZ ceramic possessed a high level of unipolar strain (∼0.15%) and maintained a smaller variation of ±12% under the corresponding electric field of 60 kV cm⁻¹ at 10 Hz from 25 °C to 175 °C. d₃₃^*, which was calculated according to the unipolar strain at 60 kV cm⁻¹, was 230 pm V⁻¹ and remained stable below 100 °C. Therefore, our work provided a new promising candidate for temperature-insensitive capacitors and piezoelectric actuators.     

Phase structure,piezoelectric, ferroelectric,and electric-field-induced strain properties of Nb-modified 0.8Bi0.5Na0.5TiO3−0.2Sr0.85Bi0.1TiO3 ceramics

0.8Bi_0.5Na_0.5Ti_(1-x)Nb_xO₃−0.2Sr_0.85Bi_0.1TiO₃ (BNT-SBT-xNb, x = 0.00, 0.01, 0.02, and 0.03) piezoelectric ceramics were prepared by traditional solid state reaction and the influence of Nb substitution on the phase structure, ferroelectric, piezoelectric, and electric-field-induced strain properties in BNT-SBT ceramics were studied. XRD results exhibited that Nb⁵⁺ ions could fully diffuse into BNT-SBT structure to form a solid solution when x = 0.01. P-E loops and S-E curves suggested that the ferroelectric phase transformed to ergodic relaxor state (FE-to-ER) with the increasing the amount of Nb additive, indicating the ferroelectric long-ranged order was disturbed by the excess of Nb. With increasing Nb doping, phase transition temperature from normal ferroelectric to ergodic relaxor (short for T_F-R) could be reduced from 120 °C to 40 °C. Furthermore, for sample with x = 0.01, the normalized strain d₃₃^* got a maximum value ~571 pm/V due to the phase transition from ergodic relaxor to ferroelectric (ER-to-FE) under electric field.     

Effect of Li2O–V2O5 on the low temperature sintering and microwave dielectric properties of Li1.0Nb0.6Ti0.5O3 ceramics

Li₂O–Nb₂O₅–TiO₂ based ceramic systems have been the candidate materials for LTCC application, due to their high dielectric constant and Q × f value and controllable temperature coefficient in the microwave region. However, the sintering temperature was relatively higher (above 1100 °C) for practical application. In this study, dielectric properties of Li_(1+x−y)Nb_(1−x−3y)Ti_(x+4y)O₃ solid solution were studied with different x and y contents and among them, the Li_1.0Nb_0.6Ti_0.5O₃ composition (x = 0.1, y = 0.1) was selected, due to its reasonable dielectric properties to determine the possibility of low temperature sintering. The effects of 0.17Li₂O–0.83V₂O₅, as a sintering agent, on sinterability and microwave dielectric properties of Li_1.0Nb_0.6Ti_0.5O₃ ceramics were investigated as a function of the sintering agent content and sintering temperature. With addition of 0.17Li₂O–0.83V₂O₅ above 0.5 wt%, the specimens were well densified at a relatively lower temperature of 850 °C. Only slight decrease in apparent density was observed with increasing 0.17Li₂O–0.83V₂O₅ content above 0.75 wt%. In the case of 0.5 wt% 0.17Li₂O–0.83V₂O₅ addition, the values of dielectric constant and Q × f reached maximum. Further addition caused inferior microstructure, resulting in degraded dielectric properties. For the specimens with 0.5 wt% 0.17Li₂O–0.83V₂O₅ sintered at 850 °C, dielectric constant, Q × f and TCF values were 64.7, 5933 GHz and 9.4 ppm per °C, respectively.     

Effect of CuO/MnO additives on microstructure and microwave dielectric properties of 3ZrO2-3TiO2-ZnNb2O6 ceramics

The effect of CuO/MnO additives on phase composition, microstructures, sintering behavior, and microwave dielectric properties of 3ZrO₂-3TiO₂-ZnNb₂O₆ (3Z-3T-ZN) ceramics prepared by conventional solid-state route were systematically investigated. CuO/MnO doped ceramics exhibited a main phase of α-PbO₂-structured ZrTi₂O₆ and a secondary phase of rutile TiO₂. SEM results showed that the grain size of MnO doped ceramics became larger with increasing amount of dopants. The presence of CuO/MnO additives effectively reduced the sintering temperature of 3Z-3T-ZN ceramics to 1220 °C. MnO doped into ceramics could enhance the Q×f values significantly. The 0.5 wt% CuO doped 3Z-3T-ZN ceramics with 0.5 wt% of MnO, sintered at 1220 °C for 4 h, was measured to show superior microwave dielectric properties, with an ε_r of 41.02, a Q×f value of 44,230 GHz (at 5.2 GHz), and τ_f value of +2.32 ppm/°C.     

Microstructure and electrical properties of relaxor (1 − x)[(K0.5Na0.5)0.95Li0.05](Nb0.95Sb0.05)O3–xBaTiO3 piezoelectric ceramics

In order to solve the low temperature stability of electrical properties in KNN-based ceramics, (1 ? x)[(K_0.5Na_0.5)_0.95Li_0.05](Nb_0.95Sb_0.05)O₃–xBaTiO₃ [(1 ? x)KNLNS–xBT] lead-free piezoelectric ceramics were prepared by the conventional solid-state sintering method. The introduction of BT stabilizes the tetragonal phase of KNLNS ceramics at room temperature, results in a typical ferroelectric relaxor behavior, and shifts the polymorphic phase transition to below room temperature. Moreover, there is a strong BaTiO₃ concentration dependence of relaxor behavior and electrical properties, and the ceramic with x = 0.005 exhibits optimum electrical properties and typical relaxor behavior (d₃₃ = 269 pC/N, k_p = 0.50, ?_r = 1371, tan δ = 0.03, T_C ～ 349 °C and γ = 1.88024). These results indicate that the BT is an effective way to improve the temperature stability as well as the electrical properties of KNN-based ceramics.