Preparation and characterization of Pb(Lu1/2Nb1/2)O3–Pb(In1/2Nb1/2)O3–PbTiO3 ternary ferroelectric ceramics with high phase transition temperatures

To explore new relaxor‐PbTiO₃ systems for high‐power and high‐temperature electromechanical applications, a ternary ferroelectric ceramic system of Pb(Lu_1/2Nb_1/2)O₃–Pb(In_1/2Nb_1/2)O₃–PbTiO₃ (PLN–PIN–PT) have been investigated. The phase structure, dielectric, piezoelectric, and ferroelectric properties of the as‐prepared PLN–PIN–PT ceramics near the morphotropic phase boundary (MPB) were characterized. A high rhombohedral‐tetragonal phase transition temperature T_R‐T of 165°C and a high Curie temperature T_C of 345°C, together with a good piezoelectric coefficient d₃₃ of 420 pC/N, were obtained in 0.38PLN–0.20PIN–0.42PT ceramics. Furthermore, for (0.8?x)PLN–0.2PIN–xPT ceramics, the temperature‐dependent piezoelectric coefficients, coercive fields and electric‐field‐induced strains were further studied. At 175°C, their coercive fields were found to be above 9.5 kV/cm, which is higher than that of PMN–PT and soft P5H ceramics at room temperature, indicating PLN–PIN–PT ceramics to be one of the promising candidates in piezoelectric applications under high‐driven fields. The results presented here could benefit the development of relaxor‐PbTiO₃ with enhanced phase transition temperatures and coercive fields.     

Perovskite‐Structured BiFeO3–Bi(Zn1/2Ti1/2)O3–PbTiO3 Solid Solution Piezoelectric Ceramics with Curie Temperature About 700°C

In this article, perovskite‐structured BiFeO₃–Bi(Zn_1/2Ti_1/2)O₃–PbTiO₃ (BF–BZT–PT) ternary solid solutions were prepared with traditional solid‐state reaction method and demonstrated to exhibit a coexistent phase boundary (CPB) with Curie temperature of T_C~700°C in the form of ceramics with microstructure grain size of several micron. It was found that those CPB ceramics fabricated with conventional electroceramic processing are mechanically and electrically robust and can be poled to set a high piezoelectricity for the ceramics prepared with multiple calcinations and sintering temperature around 750°C. A high piezoelectric property of T_C = 560°C, d₃₃ = 30 pC/N, ε₃₃^T/ε₀ = 302, and tanδ = 0.02 was obtained here for the CPB 0.53BF–0.15BZT–0.32PT ceramics with average grain size of about 0.3 μm. Primary experimental investigations found that the enhanced piezoelectric response and reduced ferroelectric Curie temperature are closely associated with the small grain size of microstructure feature, which induces lattice structural changes of increased amount ratio of rhombohedral‐to‐tetragonal phase accompanying with decreased tetragonality in the CPB ceramics. Taking advantage of structural phase boundary feature like the Pb(Zr,Ti)O₃ systems, through adjusting composition and microstructure grain size, the CPB BF–BZT–PT ceramics is a potential candidate to exhibit better piezoelectric properties than the commercial K‐15 Aurivillius‐type bismuth titanate ceramics. Our essay is anticipated to excite new designs of high–temperature, high–performance, perovskite‐structured, ferroelectric piezoceramics and extend their application fields of piezoelectric transducers.     

Characterization of the High‐Temperature Ferroelectric (100−x−y)BiScO3–(x)Bi(Zr0.5Zn0.5)O3–(y)PbTiO3 Perovskite Ternary Solid Solution

Ternary compositions based on Bi(B′B″)O₃–PbTiO₃‐type compounds have been investigated for high‐temperature piezoelectric applications. Compositions in the ternary were chosen to be near the binary morphotropic phase boundary (MPB) composition of BiScO₃–PbTiO₃ (BS–PT). Ternary compositions in (100?x?y)BiScO₃–(x)Bi(Zr_0.5Zn_0.5)O₃–(y)PbTiO₃ [(100?x?y)BS–xBZZ–yPT] have been investigated with x ≤ 7.5. For compositions with x > 10, the Curie temperature (T_C) decreased below 400°C. Dielectric, piezoelectric, and electromechanical properties were characterized as a function of temperature, frequency, and electric field. Small additions of BZZ were shown to increase the electromechanical properties with only a small loss in T_C. The electromechanical properties were temperature stable up to the depoling temperature. The most promising composition exhibited a T_C of 430°C, piezoelectric coefficient (d₃₃) of 520 pC/N, and a planar coupling factor (k_p) of 0.45 that remained unchanged up to depoling temperature at 385°C.     

Phase Diagram and Properties of High TC/TR−T Pb(In1/2Nb1/2) O3–Pb(Zn1/3Nb2/3)O3–PbTiO3 Ferroelectric Ceramics

A ternary ferroelectric ceramic system, (1?x?y)Pb(In_1/2Nb_1/2)O₃–xPb(Zn_1/3Nb_2/3)O₃–yPbTiO₃ (PIN–PZN–PT, x = 0.21, 0.27, 0.36, 0.42), was prepared using a two‐step precursor method. The phase structure, dielectric, piezoelectric, and ferroelectric properties of the ternary ceramics were systematically investigated. A morphotropic phase boundary (MPB) was identified by X‐ray diffraction. The optimum piezoelectric and electromechanical properties were achieved for a composition close to MPB (0.5PIN–0.21PZN–0.29PT), where the piezoelectric coefficient d₃₃, planar electromechanical coupling factor k_p, and remnant polarization P_r are 660 pC/N,72%, and 45 μC/cm², respectively. The Curie temperature T_C and rhombohedral to tetragonal phase transition temperature T_R?T were also derived by temperature dependence of dielectric measurements. The strongly “bended” MPB in the PIN–PT system was found to be “flattened” after addition of PZN in the PIN–PT–PZN system. The results demonstrate a possibility of growing ferroelectric single crystals with high electromechanical properties and expanded range of application temperature.     

Crystal Structure and Electrical Properties of Lead‐Free (1 − x)BaTiO3–x(Bi1/2A1/2)TiO3 (A = Ag,Li, Na,K, Rb,Cs) Ceramics

Ceramics of solid solutions (1  ?  x)BaTiO₃–x(Bi_1/2A_1/2)TiO₃ (A = Ag, Li, Na, K, Rb, Cs, x ≤ 0.20) were prepared and their crystal structures, dielectric, ferroelectric, and piezoelectric properties were investigated. It was found that (Bi_1/2A_1/2)TiO₃‐type doping compounds broadened the temperature range of the tetragonal phase in BaTiO₃ and all the compositions examined displayed a tetragonal structure at room temperature. The Curie temperature (T_C) was observed to increase with respect to pure BaTiO₃ to the range 140°C–210°C through solid solution. Remanent polarization (P_r) tended to decrease with increased content of doping compound, whereas the coercive field (E_C) rose and piezoelectric coefficient (d₃₃) fell. The highest d₃₃ value in the solid solutions was observed in 0.97BaTiO₃–0.03(Bi_1/2Ag_1/2)TiO₃ at 90 pC/N.     

Normal‐Relaxor‐Diffuse Ferroelectric Phase Transition and Electrical Properties of Bi(Mg1/2Ti1/2)3–PbZrO3–PbTiO3 Solid Solution Ceramics Near the Morphotropic Phase Boundary

Perovskite‐type xBi(Mg_1/2Ti_1/2)O₃–(0.56 ? x)PbZrO₃–0.44PbTiO₃ (xBMT–PZ–PT) ternary solid solution ceramics were synthesized via a conventional solid‐state reaction method. The phase transition behaviors, dielectric, ferroelectric, and piezoelectric properties were investigated as a function of the BMT content. The X‐ray diffraction analysis showed that the tetragonality of xBMT–PZ–PT was enhanced with increasing the BMT content, and a morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases was identified approximately in the composition of x = 0.08. In addition, the dielectric diffuseness and frequency dispersion behavior were induced with the addition of BMT and a normal‐relaxor‐diffuse ferroelectric transformation was observed from the PZ‐rich side to the BMT‐rich side. The electrical properties of xBMT–PZ–PT ceramics exhibit obviously compositional dependence. The x = 0.08 composition not only possessed the optimum properties with ε^T₃₃/ε₀ = 1450, Q_m = 69, d₃₃ = 390 pC/N, k_p = 0.46, P_r = 30 μC/cm², E_c = 1.4 kV/mm, T_c = 325°C, and a strain of 0.174% (d₃₃^* = 436 pm/V) under an electric field of 4 kV/mm as a result of the coexistence of two ferroelectric phases near the MPB, but also owned a good thermal‐depolarization behavior with a d₃₃ value of >315 pC/N up to 290°C and a frequency‐insensitive strain behavior.     

Large Piezoelectric Response and Polarization in Relaxor Ferroelectric PbTiO3–Bi(Ni1/2Zr1/2)O3

New binary system (1?x) PbTiO₃?xBi(Ni_1/2Zr_1/2)O₃ (PT–100x BNZ) with x ≤ 0.45 were synthesized via solid‐state reaction route. A morphotropic phase boundary (MPB) was identified around x = 0.40 by X‐ray diffraction (XRD) method. The ceramics with MPB composition exhibit enhanced ferroelectric properties. A large piezoelectric coefficient (d₃₃) up to 400 pC/N was obtained for the PT–40BNZ, which is comparable with the PbTiO₃–BiScO₃ (PT–BS, 450 pC/N).The frequency dependence of dielectric permittivity of PT–40BNZ shows characteristic of a strong relaxor feature and a transition temperature around 290°C (1 MHz). Temperature effect on the unipolar strain was also investigated. The present system with high d₃₃ is a competitive piezoelectric material, as no expensive oxide is used here compared with the PT–BS.     

Piezoelectric Property and Strain Behavior of Pb(Yb0.5Nb0.5)O3–PbHfO3–PbTiO3 Polycrystalline Ceramics

(1?x)Pb(Hf_1?yTi_y)O₃–xPb(Yb_0.5Nb_0.5)O₃ (x = 0.10–0.44, y = 0.55–0.80) ceramics were fabricated. The morphotropic phase boundary (MPB) of the ternary system was determined by X‐ray powder diffraction. The optimum dielectric and piezoelectric properties were achieved in 0.8Pb(Hf_0.4Ti_0.6)O₃–0.2Pb(Yb_0.5Nb_0.5)O₃ ceramics with MPB composition, where the dielectric permittivity ε_r, piezoelectric coefficient d₃₃, planar electromechanical coupling k_p, and Curie temperature T_c were found to be on the order of 1930,480 pC/N, 62%, and 360°C, respectively. The unipolar strain behavior was evaluated as a function of applied electric field up to 50 kV/cm to investigate the strain nonlinearity and domain wall motion under large drive field, where the high field piezoelectric d₃₃* was found to be 620 pm/V for 0.82Pb(Hf_0.4Ti_0.6)O₃–0.18Pb(Yb_0.5Nb_0.5)O₃. In addition, Rayleigh analysis was carried out to study the extrinsic contribution, where the value was found to be in the range 2%–18%.     

Low‐temperature sintering and enhanced piezoelectric properties of random and textured PIN–PMN–PT ceramics with Li2CO3

Low‐temperature sintered random and textured 36PIN–30PMN–34PT piezoelectric ceramics were successfully synthesized at a temperature as low as 950°C using Li₂CO₃ as sintering aids. The effects of Li₂CO₃ addition on microstructure, dielectric, ferroelectric, and piezoelectric properties in 36PIN–30PMN–34PT ternary system were systematically investigated. The results showed that the grain size of the specimens increased with the addition of sintering aids. The optimum properties for the random samples were obtained at 0.5 wt% Li₂CO₃ addition, with piezoelectric constant d₃₃ of 450 pC/N, planar electromechanical coupling coefficient k_p of 49%, peak permittivity ε_max of 25 612, remanent polarization P_r of 36.3 μC/cm². Moreover, the low‐temperature‐sintered textured samples at 0.5 wt% Li₂CO₃ addition exhibited a higher piezoelectric constant d₃₃ of 560 pC/N. These results indicated that the low‐temperature‐sintered 36PIN–30PMN–34PT piezoelectric ceramics were very promising candidates for the multilayer piezoelectric applications.     

Pb(In1/2Nb1/2)O3-PbZrO3-PbTiO3 ternary ceramics with temperature-insensitive and superior piezoelectric property

The development of ferroelectric ceramics with both large piezoelectric responses and broad service temperature range is still a key challenge for practical applications due to the so-called d₃₃-T_C trade-off. Here we report the strategy to utilize the synergistic contribution of morphotropic phase boundary and enhanced local structural heterogeneity, in which an excellent piezoelectric coefficient d₃₃ of 680 pC/N and a high Curie temperature of 330 ℃ are simultaneously achieved in Sm modified 0.25PIN-0.325PZ-0.425PT ceramics. The underlying mechanism responsible for the high dielectric and piezoelectric properties is studied based on cryogenic dielectric measurement and Rayleigh analysis. Of particular interest is that, a high field-induced strain of 0.19% is achieved in 0.25PIN-0.32PZ-0.43PT at electric field of 20 kV/cm, corresponding to a piezoelectric d₃₃ * of 945 pm/V, showing an excellent temperature stability with minimal variation of 7% up to 310 °C. This work demonstrates the introduction of high temperature end members and rare earth doping are conducive to ferroelectric solid solutions with desired broad usage temperature range and superior piezoelectric properties, which will greatly benefit high temperature actuator applications.     

Structures and Properties of Pb(Zr0.5Ti0.5)O3−Pb(Zn1/3Nb2/3)O3− Pb(Ni1/3Nb2/3)O3 Ceramics for Energy Harvesting Devices

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(Zr_0.5Ti_0.5)O₃?yPb(Zn_1/3Nb_2/3)O₃?(1?x?y)Pb(Ni_1/3Nb_2/3)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 ε₃₃^T/ε₀ decreases faster than the d₃₃ coefficient at this side.     

Remarkable piezoelectricity and stable high‐temperature dielectric properties of quenched BiFeO3–BaTiO3 ceramics

Effects of quenching process on dielectric, ferroelectric, and piezoelectric properties of 0.71BiFeO₃?0.29BaTiO₃ ceramics with Mn modification (BF–BT?xmol%Mn) were investigated. The dielectric, ferroelectric, and piezoelectric properties of BF–BT?xmol%Mn were improved by quenching, especially to the BF–BT?0.3 mol%Mn ceramics. The dielectric loss tanδ of quenched BF–BT?0.3 mol%Mn ceramics was only 0.28 at 500°C, which was half of the slow cooling one. Meanwhile, the remnant polarization P_r of quenched BF–BT?0.3 mol%Mn ceramics increased to 21 μC/cm². It was notable that the piezoelectric constant d₃₃ of quenched BF–BT?0.3 mol%Mn ceramics reached up to 191 pC/N, while the T_C was 530°C, showing excellent compatible properties. The BF–BT?xmol%Mn system ceramics showed to obey the Rayleigh law within suitable field regions. The Rayleigh law results indicated that the extrinsic contributions to the dielectric and piezoelectric responses of quenched BF–BT?xmol%Mn ceramics were larger than the unquenched ceramics. These results presented that the quenched BF–BT?xmol%Mn ceramics were promising candidates for high‐temperature piezoelectric devices.     

Microstructure,Ferroelectric, Piezoelectric,and Ferromagnetic Properties of Sc‐Modified BiFeO3–BaTiO3 Multiferroic Ceramics with MnO2 Addition

0.725BiFe_1?xSc_xO₃–0.275BaTiO₃ + y mol% MnO₂ multiferroic ceramics were fabricated by a conventional ceramic technique and the effects of Sc doping and sintering temperature on microstructure, multiferroic, and piezoelectric properties of the ceramics were studied. The ceramics can be well sintered at the wide low sintering temperature range 930°C–990°C and possess a pure perovskite structure. The ceramics with x/y = 0.01–0.02/1.0 sintered at 960°C possess high resistivity (~2 × 10⁹ Ω·cm), strong ferroelectricity (P_r = 19.1–20.4 μm/cm²), good piezoelectric properties (d₃₃ = 127–128 pC/N, k_p = 36.6%–36.9%), and very high Curie temperature (618°C–636°C). The increase in sintering temperature improves the densification, electric insulation, ferroelectric, and piezoelectric properties of the ceramics. A small amount of Sc doping (x ≤ 0.04) and the increase in the sintering temperature significantly enhance the ferromagnetic properties of the ceramics. Improved ferromagnetism with remnant magnetization M_r of 0.059 and 0.10 emu/g and coercive field H_c of 2.51 and 2.76 kOe are obtained in the ceramics with x/y = 0.04/1.0 (sintered at 960°C) and 0.02/1.0 (sintered at 1050°C), respectively. Because of the high T_C (636°C), the ceramic with x/y = 0.02/1.0 shows good temperature stability of piezoelectric properties. Our results also show that the addition of MnO₂ is essential to obtain the ceramics with good electrical properties and electric insulation.     

Properties of Low‐Temperature Sintering PNN–PMW–PSN–PZT Piezoelectric Ceramics with Ba(Cu1/2W1/2)O3 Sintering Aids

Piezoelectric ceramics Pb(Ni_1/3Nb_2/3)O₃–Pb(Mg_1/2W_1/2)O₃–Pb(Sb_1/2Nb_1/2)O₃–Pb(Zr_0.39Ti_0.61)O₃ with Ba(Cu_1/2W_1/2)O₃ sintering aids were fabricated using economical industrial oxide powders and their piezoelectric, dielectric, and ferroelectric properties were investigated in order to develop low‐temperature sintering ceramics for multilayer piezoelectric actuators. A quadratic formula and the Curie–Weiss law reveal that the ceramics are typical displacive‐type ferroelectric relaxors. The ceramics sintered as low as 900°C have good piezoelectric properties of d₃₃ = 551 pC/N, k_p = 0.52, ε_r = 3583, tgδ = 0.02, and T_C = 161°C, which is much promising to manufacture multilayer piezoelectric transducers.     

Structure Evolution and Electrical Properties of Y3+‐Doped Ba1−xCaxZr0.07Ti0.93O3 Ceramics

Lead free piezoelectric ceramics of Y³⁺‐doped Ba_1?xCa_xZr_0.07Ti_0.93O₃ with x = 0.05, 0.10, and 0.15 were prepared. Composition and temperature‐dependent structural phase evolution and electrical properties of as‐prepared ceramics were studied systematically by X‐ray diffraction, Raman spectroscopy, impedance analyzer, ferroelectric test system, and unipolar strain measurement. Composition with x = 0.10 performs a good piezoelectric constant d₃₃ of 363 pC/N, coercive field E_c of 257 V/mm, remanent polarization P_r of 14.5 μC/cm², and a Curie temperature T_m of 109°C. High‐resolution X‐ray diffraction was introduced to indicate presence of orthorhombic phase. Converse piezoelectric constant d₃₃* of x = 0.10 composition performed better temperature stability in the range from 50°C to 110°C. That means decreasing orthorhombic–tetragonal phase transition temperature could be an effective way to enlarge its operating temperature range.     

Photoluminescence and Temperature Dependent Electrical Properties of Er‐Doped 0.94Bi0.5Na0.5TiO3‐0.06BaTiO3 Ceramics

Er‐doped 0.94Bi_0.5Na_0.5TiO₃‐0.06BaTiO₃ (BNT‐6BT: xEr, x is the molar ratio of Er³⁺ doping) lead‐free piezoceramics with x = 0–0.02 were prepared and their multifunctional properties have been comprehensively investigated. Our results show that Er‐doping has significant effects on morphology of grain, photoluminescence, dielectric, and ferroelectric properties of the ceramics. At room temperature, the green (550 nm) and red (670 nm) emissions are enhanced by Er‐doping, reaching the strongest emission intensity when x = 0.0075. The complex and composition‐dependent effects of electric poling on photoluminescence also have been measured. As for electrical properties, on the one hand, Er‐doping tends to flatten the dielectric constant‐temperature (ε_r‐T) curves, leading to temperature‐insensitive dielectric constant in a wide temperature range (50°C–300°C). On the other hand, Er‐doping significantly decreases the ferroelectric‐relaxor transition temperature (T_F–R) and depolarization temperature (T_d), with the T_F–R decreasing from 76°C to 42°C for x = 0–0.02. As a result, significant composition‐dependent electrical features were found in ferroelectric and piezoelectric properties at room temperature. In general, piezoelectric and ferroelectric properties tend to become weaker, as confirmed by the composition‐dependent piezoelectric coefficient (d₃₃), planar coupling factor (k_p), and the shape of polarization‐electric field (P–E), current‐electric field (J–E), bipolar/unipolar strain‐electric field (S–E) curves. Furthermore, to understand the relationship between the T_F–R/T_d and the electrical properties, the composition of x = 0.0075 has been intensively studied. Our results indicate that the BNT‐6BT: xEr with appropriate Er‐doping may be a promising multifunctional material with integrated photoluminescence and electrical properties for practical applications.     

Dielectric and Piezoelectric Properties of (1−x)K0.5Bi0.5TiO3–xBa(Ti0.8Zr0.2)O3 Ceramics

The properties of relaxor ceramics in the compositional series (1?x)K_0.5Bi_0.5TiO₃–xBa(Ti_0.8Zr_0.2)O₃ have been investigated. Values of T_m, the temperature of maximum relative permittivity, decreased from 380°C at x = 0.0 to below room temperature for x > 0.7. Compositions x = 0.1 and 0.2 were piezoelectric and ferroelectric. The maximum value of d₃₃ piezoelectric charge coefficient, 130 pC/N, and strain, 0.14%, occurred at x = 0.1. Piezoelectric properties of x = 0.1 were retained after thermal cycling from room temperature to 220°C, consistent with results from high‐temperature X‐ray diffraction indicating a transition to single‐phase cubic at ~300°C.     

High‐temperature piezoelectric properties of 0‐3 type CaBi4Ti4O15:x wt%BiFeO3 composites

The 0‐3 type CaBi₄Ti₄O₁₅:30 wt%BiFeO₃ composite shows much better high‐temperature piezoelectric properties than the single‐phase CaBi₄Ti₄O₁₅ or BiFeO₃ ceramics. The composite with 0‐3 type connectivity exhibits a high density of 7.01 g/cm³, a saturated polarization of 21.5 μC/cm² and an enhanced piezoelectric d₃₃ of 25 pC/N. After the poled composite was annealed at 600°C, its d₃₃ is 21 pC/N at room temperature. Resistance of the composite decreases slowly from 10⁹ ohm at 20°C to ~10⁵ ohm at 500°C. Furthermore, the poled composite shows strong radial and thickness dielectric resonances at 20°C‐500°C.     

Properties and structures of nonstoichiometric (K,Na)NbO3‐based lead‐free ceramics

The 0.968[(K_0.48Na_0.52)]Nb_0.95+xSb_0.05O₃–0.032(Bi_0.5Na_0.5)ZrO₃ [KNN_xS–BNZ] lead‐free ceramics with nonstoichiometric niobium ion were fabricated via conventional solid‐state sintering technique and their piezoelectric, dielectric and ferroelectric properties were investigated. When x = 0.010, enhanced piezoelectric properties (d₃₃ ≈ 421 pC/N and k_p ≈ 0.47) were obtained due to the construction of rhombohendral—tetragonal phase boundary near room temperature. The KNN_xS–BNZ ceramics possesses enhanced Curie temperature (T_c) with improved piezoelectric constant. A large d₃₃ of ~421 pC/N and a high T_c ~256°C can be simultaneously induced in the ceramics with x = 0.010. Especially, good thermal stability was observed in a broad temperature range. The results indicated that our work could benefit development of KNN‐based ceramics and widen their application range.     

Composition and temperature dependence of structure and piezoelectricity in (1−x)(K1−yNay)NbO3‐x(Bi1/2Na1/2)ZrO3 lead‐free ceramics

Lead‐free piezoceramics with the composition (1?x)(K_1?yNa_y)NbO₃‐x(Bi_1/2Na_1/2)ZrO₃ (KNyN‐xBNZ) were prepared using a conventional solid‐state route. X‐ray diffraction, Raman spectroscopy, and dielectric measurements as a function of temperature indicated the coexistence of rhombohedral (R) and tetragonal (T) phase, typical of a morphotropic phase boundary (MPB) as the BNZ concentration increased and by adjusting the K/Na ratio. High remnant polarization (P_r=24 μC/cm²), piezoelectric coefficient (d₃₃=320 pC/N), effective piezocoefficient ({d_{33}^*}=420 pm/V), coupling coefficient (k_p=48%), and high strain (S=0.168%) were obtained at room temperature, but significant deterioration of P_r, {d_{33}^*}, and k_p were observed by increasing from room temperature to 160°C (17.5 μC/cm², 338 pm/V, and 32%, respectively) associated with a transition to a purely T phase. Despite these compositions showing promise for room‐temperature applications, the deterioration in properties as a function of increasing temperature poses challenges for device design and remains to be resolved.