Effect of Texture on Temperature‐Dependent Properties of K0.5Na0.5NbO3 Modified Bi1/2Na1/2TiO3–xBaTiO3

Textured (1?x?y)Bi_1/2Na_1/2TiO₃–xBaTiO₃–yK_0.5Na_0.5NbO₃ (BNT–100xBT–100yKNN) ceramics with a {001} pseudocubic (pc) orientation were fabricated by templated grain growth using Bi_1/2Na_1/2TiO₃ templates. Temperature‐dependent electromechanical results demonstrate that the strain response of templated BNT–xBT–yKNN ceramics is stable from room temperature (RT) to 125°C. The temperature‐dependent strain and polarization response are compared to randomly oriented ceramics, for BNT–100xBT–2KNN (0.05 ≤ x ≤ 0.07). Textured BNT–7BT–2KNN reached a maximum 0.47% strain response at 5 kV/mm, an almost 50% increase compared to randomly oriented BNT–7BT–2KNN. Over the temperature range RT–125°C, the strain response of templated BNT–6BT–2KNN degraded from 0.38% to 0.22% (?42.1%) compared to 0.37% to 0.18% (?51.4%) for randomly oriented ceramics. The temperature‐dependent strain response suggests that templated BNT–100xBT–100yKNN ceramics are well suited for elevated temperature applications.     

Giant electromechanical strain response in lead‐free SrTiO3‐doped (Bi0.5Na0.5TiO3–BaTiO3)–LiNbO3 piezoelectric ceramics

Lead‐free 0.985[(0.94?x)Bi_0.5Na_0.5TiO₃–0.06BaTiO₃–xSrTiO₃]–0.015LiNbO₃ [(BNT–BT–xST)–LN, x=0‐0.05] piezoelectric ceramics were prepared 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 (P_r), coercive field (E_c), negative strain (S_neg) 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, S_max/E_max 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 S_max/E_max 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.     

Preparation and Electric Properties of Bi0.5Na0.5TiO3–Bi(Mg0.5Ti0.5)O3 Lead‐Free Piezoceramics

Lead‐free BNT‐based piezoceramics, (1?x)Bi_0.5Na_0.5TiO₃–xBi(Mg_0.5Ti_0.5)O₃ [(1?x)BNT–xBMT] (0.00 ≤ x ≤ 0.06) binary system, were synthesized using a conventional ceramic fabrication method. Effect of Bi(Mg_0.5Ti_0.5)O₃ (BMT) substitution on room temperature (RT) crystal structure, and temperature dependence of electric properties were investigated. The XRD indicates that a pure perovskite phase is formed. The introduction of BMT decreases E_C of BNT from 7.3 to 4.0 kV/mm, and increases d₃₃ from 58 pC/N to 110 pC/N for the x = 0.05. The system shows a typical ferroelectric (FE) polarization loop P(E) and butterfly bipolar strain‐electric S(E) curve at RT. For the composition of 0.95BNT–0.05BMT antiferroelectric (AFE) phase appears near 80°C, characterized by a constricted P(E) loop and altered bipolar S(E) butterfly, and gradually prevails with increasing temperature. Temperature dependence of dielectric constant shows that T_C increases from 310°C for pure BNT to 352°C for the x = 0.05. The results indicate that the piezoelectric properties of BNT have been improved by means of Bi(Mg_0.5Ti_0.5)O₃ substitution.     

Preparation and Electric Properties of Bi0.5Na0.5TiO3–Bi(Al0.5Ga0.5)O3 Lead‐Free Piezoceramics

A new lead‐free BNT‐based piezoelectric ceramics of (1 ? x)Bi_0.5Na_0.5TiO₃–xBi(Al_0.5Ga_0.5)O₃ (x = 0, 0.02, 0.03, 0.04, and 0.05) were synthesized using a conventional ceramic fabrication method. Their structures and electrical properties were investigated. All the samples show a typical ferroelectric P(E) loops and S(E) curves at room temperature. The optimal properties are obtained at the composition of the x = 0.03. The substitution of Bi(Al_0.5Ga_0.5)O₃ enhances piezoelectric constant and increases Curie temperature from 58 pC/N and 310°C of pure BNT to 93 pC/N and 325°C of the x = 0.03. The temperature‐dependent P(E) loops and S(E) curves of 0.97BNT–0.03BAG indicate that phase transition from ferroelectric to antiferroelectric takes place over a very wide temperature region from 80°C to 180°C. The results show that the introduction of BAG improves the electrical properties of BNT.     

ZnO‐enhanced electrical properties of Bi0.5Na0.5TiO3‐based incipient ferroelectrics

Bi_0.5Na_0.5TiO₃‐based incipient ferroelectrics with pseudocubic structure generally show weak ferro‐/piezoelectricity but giant field‐induced strains. It is difficult to artificially and smoothly improve the electrical property based on conventional chemical doping or substituting without changing the crystal structure and suppressing the strain. Here, by introducing the semiconductor ZnO into the lead‐free incipient ferroelectric ((Bi_0.5(Na_0.84K_0.16)_0.5)_0.96Sr_0.04)(Ti_0.975Nb_0.025)O₃ (BNT–2.5Nb) to form 0‐3 type composites (BNT–2.5Nb:xZnO), we experimentally illustrate that the resistance and ferro‐/piezoelectric properties can be enhanced significantly with an unchanged crystal structure and only slightly suppressed strains. For example, the remanent polarization and piezoelectric coefficient increase from 4.6 μC/cm² and 8 pC/N for x=0 to 9.0 μC/cm² and 31 pC/N for x=0.3. At the same time, the total strain only decreases from 0.140% for x=0 to 0.108% for x=0.3, whereas the negative strain increases from ?0.003% for x=0 to ?0.010% for x=0.3. And the thermal stability of d₃₃ is enhanced. The corresponding mechanism is attributed to that ZnO can form a local field, preventing the depolarization of field induced macroscopic ferroelectric domains. Our results not only provide a feasible way to tune electrical properties of BNT‐based incipient ferroelectrics, but also may stimulate further work on artificially structured high‐performance ferroelectrics.     

Large Piezoresponse and Ferroelectric Properties of (Bi0.5Na0.5)TiO3–(Bi0.5K0.5)TiO3–Bi(Mg0.5Ti0.5)O3 Thin Films Prepared by Chemical Solution Deposition

Bulk ceramic 72.5 mol%(Bi_0.5Na_0.5)TiO₃–22.5 mol%(Bi_0.5K_0.5)TiO₃–5 mol%Bi(Mg_0.5Ti_0.5)O₃ (BNT–BKT–BMgT) has previously been reported to show a large high‐field piezoelectric coefficient (d₃₃* = 570 pm/V). In this work, the same composition was synthesized in thin film embodiments on platinized silicon substrates via chemical solution deposition. Overdoping of volatile cations in the precursor solutions was necessary to achieve phase‐pure perovskite. An annealing temperature of 700°C resulted in good ferroelectric properties (P_max = 52 μC/cm² and P_r = 12 μC/cm²). Quantitative compositional analysis of films annealed at 650°C and 700°C indicated that near ideal atomic ratios were achieved. Compositional fluctuations observed through the film thickness were in good agreement with the existence of voids formed between successive spin‐cast layers, as observed with electron microscopy. Bipolar and unipolar strain measurements were performed via double laser beam interferometry and a high effective piezoelectric coefficient (d_33,f) of approximately 75 pm/V was obtained.     

Large Electromechanical Strain in Lead‐Free Binary System K0.5Bi0.5TiO3‐Bi(Mg0.5Ti0.5)O3

Solid solution formation in the lead‐free binary system (1?x)K_0.5Bi_0.5TiO₃?xBi(Mg_0.5Ti_0.5)O₃ has been studied for compositions x ≤ 0.12. X‐ray powder diffraction shows single‐phase perovskite for x < 0.1, and a mixed phase region between tetragonal and pseudocubic phases for compositions 0.04 ≤ x ≤ 0.06. Large electromechanical strains of ~0.3% at fields of 50 kV/cm are recorded in the mixed phase region, with d₃₃* (S_max/E_max) values of ~600 pm/V. The materials sustain polarization at low electric fields with remnant polarization ~18 μC/cm² and coercive field ~20 kV/cm for x = 0.06. Relative permittivity‐temperature plots display relaxor characteristics, with peak temperature ~340°C.     

Dielectric Relaxor Evolution and Frequency‐Insensitive Giant Strains in (Bi0.5Na0.5)TiO3‐Modified Bi(Mg0.5Ti0.5)O3–PbTiO3 Ferroelectric Ceramics

The 0.45Bi(Mg_0.5Ti_0.5)O₃–(0.55 ? x)PbTiO₃–x(Bi_0.5Na_0.5)TiO₃ (BMT–PT–xBNT) ternary solid solution ceramics were prepared via a conventional solid‐state reaction method; the evolution of dielectric relaxor behavior and the electrostrain features were investigated. The XRD and dielectric measurements showed that all studied compositions own a single pseudocubic perovskite structure and undergo a diffuse‐to‐relaxor phase transition owing to the evolution of the domain from a frozen state to a dynamic state. The formation of the above dielectric relaxor behavior was further confirmed by a couple of measurements such as polarization loops, polarization current density curves, as well as bipolar strain loops. A large strain value of ~0.41% at a driving field of 7 kV/mm (normalized strain d₃₃* of ~590 pm/V) was obtained at room temperature for the composition with x = 0.32, which is located near the boundary between ergodic and nonergodic relaxor. Moreover, this electric field‐induced large strain was found to own a frequency‐insensitive characteristic.     

Composition‐ and Temperature‐Dependent Large Strain in (1−x)(0.8Bi0.5Na0.5TiO3–0.2Bi0.5K0.5TiO3)– xNaNbO3 Ceramics

Ternary solid solutions of (1 ? x)(0.8Bi_0.5Na_0.5TiO₃–0.2Bi_0.5K_0.5TiO₃)– xNaNbO₃ (BNKT–xNN) lead‐free piezoceramics were fabricated using a conventional solid‐state reaction method. Pure BNKT composition exhibited an electric‐field‐induced irreversible structural transition from pseudocubic to ferroelectric rhombohedral phase at room temperature. Accompanied with the ferroelectric‐to‐relaxor temperature T_F‐R shifted down below room temperature as the substitution of NN, a compositionally induced nonergodic‐to‐ergodic relaxor transition was presented, which featured the pinched‐shape polarization and sprout‐shape strain hysteresis loops. A strain value of ~0.445% (under a driving field of 55 kV/cm) with large normalized strain of ~810 pm/V was obtained for the composition of BNKT–0.04NN, and the large strain was attributed to the reversible electric‐field‐induced transition between ergodic relaxor and ferroelectric phase.     

Thermally-stable large strain in Bi(Mn0.5Ti0.5)O3 modified 0.8Bi0.5Na0.5TiO3-0.2Bi0.5K0.5TiO3 ceramics

(1-x)[0.8Bi_0.5Na_0.5TiO₃-0.2Bi_0.5K_0.5TiO₃]-xBi(Mn_0.5Ti_0.5)O₃ (x = 0–0.06, BNKMT100x) lead-free ferroelectric ceramics were prepared via solid state reaction method. Bi(Mn_0.5Ti_0.5)O₃ induces a structure transition from rhombohedral-tetragonal morphotropic phases to pseudo-cubic phase. Moreover, the wide range of compositions within x = 0.03–0.055 exhibit large strain of 0.31%–0.41% and electrostrictive coefficient of 0.027–0.041 m⁴/C². Especially, at x = 0.04, the large strain and electrostrictive coefficient are nearly temperature-independent in the range of 25–100 °C. The impedance analysis shows the large strain and electrostrictive coefficient originate from polar nanoregions response due to the addition of Bi(Mn_0.5Ti_0.5)O₃.     

Microstructure and Electrical Properties of Nonstoichiometric 0.94(Na0.5Bi0.5+x)TiO3–0.06BaTiO3 Lead‐Free Ceramics

0.94(Na_0.5Bi_0.5+x)TiO₃–0.06BaTiO₃ (x = ?0.04, 0, 0.02; named NB_0.46T‐6BT, NB_0.50T‐6BT, NB_0.52T‐6BT, respectively) lead‐free piezoelectric ceramics were prepared via the solid‐state reaction method. Effects of Bi³⁺ nonstoichiometry on microstructure, dielectric, ferroelectric, and piezoelectric properties were studied. All ceramics show typical X‐ray diffraction peaks of ABO₃ perovskite structure. The lattice parameters increase with the increase in the Bi³⁺ content. The electron probe microanalysis demonstrates that the excess Bi₂O₃ in the starting composition can compensate the Bi₂O₃ loss induced during sample processing. The size and shape of grains are closely related to the Bi³⁺ content. For the unpoled NB_0.50T‐6BT and NB_0.52T‐6BT, there are two dielectric anomalies in the dielectric constant–temperature curves. The unpoled NB_0.46T‐6BT shows one dielectric anomaly accompanied by high dielectric constant and dielectric loss at low frequencies. After poling, a new dielectric anomaly appears around depolarization temperature (T_d) for all ceramics and the T_d values increase with the Bi³⁺ amount decreasing from excess to deficiency. The diffuse phase transition character was studied via the Curie–Weiss law and modified Curie–Weiss law. The activation energy values obtained via the impedance analysis are 0.69, 1.05, and 1.16 eV for NB_0.46T‐6BT, NB_0.50T‐6BT and NB_0.52T‐6BT, respectively, implying the change in oxygen vacancy concentration in the ceramics. The piezoelectric constant, polarization, and coercive field of the ceramics change with the variation in the Bi³⁺ content. The Rayleigh analysis suggests that the change in electrical properties of the ceramics with the variation in the Bi³⁺ amount is related to the effect of oxygen vacancies.     

Temperature‐Dependent Phase Transitions in the Lead‐Free Piezoceramics (1 – x – y)(Bi1/2Na1/2)TiO3–xBaTiO3–y(K0.5Na0.5)NbO3 Observed by in situ Transmission Electron Microscopy and Dielectric Measurements

Lead‐free piezoelectric (1 – x – y)(Bi_1/2Na_1/2)TiO₃–xBaTiO₃–y(K_0.5Na_0.5)NbO₃ (BNT–BT–KNN) ceramics were examined in situ under increasing temperature in the transmission electron microscope. Changing superstructure reflections indicate a transition from rhombohedral to tetragonal to cubic phase with broad coexistence regions. The additional evolution of the microstructure in combination with dielectric measurements leads to a model of two relaxor‐type phase evolutions with temperature.     

Ultra‐Wide Temperature Stable Dielectrics Based on Bi0.5Na0.5TiO3–NaNbO3 System

The microstructure, phase structure, ferroelectric, and dielectric properties of (1?x)Bi_0.5Na_0.5TiO₃‐xNaNbO₃ [(1?x)BNT‐xNN] ceramics conventionally sintered in the temperature range of 1080°C–1120°C were investigated as a candidate for capacitor dielectrics with wide temperature stability. Perovskite phase with no secondary impurity was observed by XRD measurement. With increasing NN content, (1?x)BNT‐xNN was found to gradually transform from ferroelectric (x = 0–0.05) to relaxor (x = 0.10–0.20) and then to paraelectric state (x = 0.25–0.35) at room temperature, indicated by P–I–E loops analysis, associated with greatly enhanced dielectric temperature stability. For the samples with x = 0.25–0.35, the temperature coefficient of capacitance (TCC) was found <11% in an ultra‐wide temperature range of ?60°C–400°C with moderate dielectric constant and low dielectric loss, promising for temperature stable capacitor applications.     

Large Strain Response and Fatigue‐Resistant Behavior in Ternary Bi0.5Na0.5TiO3–BaTiO3–Bi(Zn0.5Ti0.5)O3 Solid Solutions

A ternary solid solution (1 ? x)(0.88Bi_0.5Na_0.5TiO₃–0.12BaTiO₃)‐xBi(Zn_0.5Ti_0.5)O₃ (BNBZT, BNBZTx) was designed and fabricated using the traditional solid‐state reaction method. The temperature and composition dependence of dielectric, ferroelectric, piezoelectric, and fatigue properties were systematically investigated and a schematic phase diagram was proposed. The substitution with Bi(Zn_0.5Ti_0.5)O₃ was found to shift the phase transition (ferroelectric tetragonal to relaxor pseudocubic phase) to lower temperatures. At a critical composition x of 0.05, large electric‐field‐induced strain response with normalized strain S_max/E_max as high as 526 pm/V was obtained under a moderate field of 4 kV/mm around room temperature. The strain exhibited good temperature stability within the temperature range of 25°C–120°C. In addition, excellent fatigue‐resistant behavior was observed in the proposed BNBZT solid solution after 10⁶ bipolar cycles. These give the BNBZT system great potential as environmental friendly solid‐state actuator.     

Ferroelectric P4mm to relaxor P4bm transition and temperature-insensitive large strains in Bi(Mg0.5Ti0.5)O3-modified tetragonal 0.875Bi0.5Na0.5TiO3-0.125BaTiO3 lead-free ferroelectric ceramics

Tetragonal phase (1–x)(0.875Bi_0.5Na_0.5TiO₃–0.125BaTiO₃)–xBi(Mg_0.5Ti_0.5)O₃ lead-free ferroelectrics were designed and fabricated by a conventional solid state route. All the specimens exhibit a tetragonal perovskite structure, and undergo a phase evolution from ferroelectric P4mm to antiferroelectric relaxor P4bm as the BMT addition increases. The critical composition x?=?0.04 makes a bridge between the both tetragonal phases, and gives a large field-induced strain of 0.30% and an adequately-large electrostrictive coefficient Q₃₃ of 0.0254?m⁴/C². To be highlighted, the field-induce strain of the composition x?=?0.04 shows an almost constant value over the temperature range of 18–100?°C, illustrating a temperature-insensitive behavior, which could be attributed to the widened gap between T_R–E and T_F–R. The temperature-insensitive large strain of the tetragonal BNT–BT–BMT composition give a promising potential for application in precision position actuators.     

Enhanced optical transmittance and energy-storage performance in NaNbO3-modified Bi0.5Na0.5TiO3 ceramics

Dielectric ceramics with both excellent energy storage and optical transmittance have attracted much attention in recent years. However, the transparent Pb-free energy-storage ceramics were rare reported. In this work, we prepared transparent relaxor ferroelectric ceramics (1 − x)Bi_0.5Na_0.5TiO₃–xNaNbO₃ (BNT–xNN) by conventional solid-state reaction method. We find the NN-doping can enhance the polarization and breakdown strength of BNT by suppressing the grain growth and restrained the reduction of Ti⁴⁺ to Ti³⁺. As a result, a high recoverable energy-storage density of 5.14 J/cm³ and its energy efficiency of 79.65% are achieved in BNT–0.5NN ceramic at 286 kV/cm. Furthermore, NN-doping can promote the densification to improve the optical transmittance of BNT, rising from ∼26% (x = 0.2) to ∼32% (x = 0.5) in the visible light region. These characteristics demonstrate the potential application of BNT–xNN as transparent energy-storage dielectric ceramics.     

Dielectric and Raman Spectroscopic Studies of Na0.5Bi0.5TiO3–BaSnO3 Ferroelectric System

A series of lead‐free perovskite solid solutions of (1 ? x) Na_0.5Bi_0.5TiO₃(NBT)—x BaSnO₃(BSN), for 0.0 ≤ x ≤ 0.15 have been synthesized using a high‐temperature solid‐state reaction route. The phase transition behaviors are studied using dielectric and Raman spectroscopic techniques. The ferroelectric to relaxor phase transition temperature (T_FR) and the temperature corresponding to maximum dielectric permittivity (T_m) are estimated from the temperature‐dependent dielectric data. Dielectric studies show diffuse phase transition around ~335°C in pure NBT and this transition temperature decreases with increase in x. The disappearance of x‐dependence of A₁ mode frequency at ~134 cm^?1 for x ≥ 0.1 is consistent with rhombohedral‐orthorhombic transition. In situ temperature dependence Raman spectroscopic studies show disappearance and discontinuous changes in the phonon mode frequencies across rhombohedral (x < 0.1)/orthorhombic (x ≥ 0.1) to tetragonal transition.     

Enhanced pyroelectric properties in (Bi0.5Na0.5)TiO3–BiAlO3–NaNbO3 ternary system lead‐free ceramics

High pyroelectric performance and good thermal stability of pyroelectric materials are desirable for the application of infrared thermal detectors. In this work, enhanced pyroelectric properties were achieved in a new ternary (1?x)(0.98(Bi_0.5Na_0.5)(Ti_0.995Mn_0.005)O₃–0.02BiAlO₃)–xNaNbO₃ (BNT–BA–xNN) lead‐free ceramics. The effect of NN addition on the microstructure, phase transition, ferroelectric, and pyroelectric properties of BNT–BA–xNN ceramics were investigated. It was found that the average grain size decreased as x increased to 0.03, whereas increased with further NN addition. The pyroelectric coefficient p at room temperature (RT) was significantly increased from 3.87 × 10^?8Ccm^?2K^?1 at x = 0 to 8.45 × 10^?8Ccm^?2K^?1 at x = 0.03. The figures of merit (FOMs), F_i, F_v and F_d, were also enhanced with addition of NN. Because of high p (7.48 × 10^?8Ccm^?2K^?1) as well as relatively low dielectric permittivity (~370) and low dielectric loss (~0.011), the optimal FOMs at RT were obtained at x = 0.02 with F_i = 2.66 × 10^?10 m/V, F_v = 8.07 × 10^?2 m²/C, and F_d = 4.22 × 10^?5 Pa^?1/2, which are superior to other reported lead‐free ceramics. Furthermore, the compositions with x ≤ 0.03 exhibited excellent temperature stability in a wide temperature range from 20 to 80°C because of high depolarization temperature (≥110°C). Those results unveil the potential of BNT–BA–xNN ceramics for infrared detector applications.     

BaTiO3 nanowires-induced phase transition and thermally stable strain in (Bi0.5Na0.5)TiO3 piezoelectric ceramics

Environment-friendly lead-free piezoceramics with high strain response and extremely excellent stability in a wide operating temperature range are critically important in practical actuator applications. Here, we develop a new strategy to tune the electrostrictive strain behavior in Bi_0.5Na_0.5TiO₃ (BNT)-based ceramics via using high aspect ratio BaTiO₃ nanowires (BT NWs) as a modifier. The addition of BT NWs generates a crossover from a typical ferroelectric (BT conventional spherical particles) to a complete ergodic relaxor (ER) phase at ambient temperature, accompanied by a large electrostrictive strain of ∼0.17% with d₃₃*(S_max/E_max) = 284 pm/V. Such a high electrostrictive strain is extremely thermally stable with only <7% fluctuation from 27 °C to 120 °C. In addition, the BT NWs-modified ceramics also exhibit acceptable fatigue endurance (<30% up to 10⁵ cycles) and frequency dependence (<20% at 10Hz–100Hz). These achieved exceptional performances can be ascribed to the BT NWs-driven complete ER phase at room temperature. The findings of this study can inspire enhanced interest in nanowires as a viable modifier to BNT-based materials due to promising potential for practical actuator applications in a wide temperature range.     

Effect of chemical inhomogeneity on domains and ferroelectric properties of Fe‐modified 0.77Bi0.5Na0.5TiO3–0.23SrTiO3

Lead‐free 0.77(Bi_0.5Na_0.5)TiO₃–0.23Sr(Ti_1?xFe_x)O₃ (x = 0, 0.04) (BNT–23STF_x) was prepared using a conventional solid‐state reaction route. The effects of Fe‐modification on the chemical homogeneity from a μm scale perspective, the core‐shell domains structures, and the ferroelectric properties were investigated. The chemical homogeneity was analyzed using energy dispersive X‐ray mapping in scanning transmission electron microscopy mode, and the field‐dependent behaviors of strain and polarization were obtained to determine the ferroelectric properties. Substituting Fe³⁺ for Ti⁴⁺ resulted in completely different electrical behavior and properties, despite similar XRD patterns and microstructures. The Fe‐substitution promoted the mobility of Sr²⁺ ions in the BNT phase and, as a consequence, the chemical homogeneity increased and the core‐domains collapsed. Extending the ceramic processing, such as milling time and sintering time, affected domain distribution and compositional inhomogeneity, which led to a gradual transformation from ferroelectric to relaxor.