Phase transition behavior of Pb(Hf,Sn, Ti,Nb)O3 ceramics at morphotropic phase boundary

The phase transition and dielectric properties of Pb_0.988(Hf_0.945Sn_xTi_0.03-xNb_0.025)O₃ ceramics (0 ≤ x ≤ 0.03, correspondingly abbreviated as H1, H2, H3, and H4) at the morphotropic phase boundary were systematically investigated. X-ray diffraction results and P-E hysteresis loops show that the dominate orthorhombic antiferroelectric phase and a small amount of the tetragonal FE phase coexist in Pb_0.988(Hf_0.945Sn_xTi_0.03-xNb_0.025)O₃ ceramics. As the Sn content increases, the antiferroelectricity is significantly enhanced, accompanied with an increased Curie temperature and sharply reduced peak dielectric constant. H1 and H2 experience an irreversible field-induced AFE-FE phase transition at the ambient temperature, and the transition from a metastable FE phase to the original AFE phase is observed in H2 when heated to 60°C. H3 and H4 experience an invertible AFE-FE phase transition, along with an enhanced forward phase switching field E_F. Moreover a decreased backward phase switching field E_A for H4 is detected as the electric field increases due to the AFE/FE coexistence. These results reveal the unique phase transition characteristics of AFE materials near the phase boundary, which is helpful for better understanding of AFE/FE materials.     

Effect of Nb doping on the relaxor behaviour of (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 ceramics

Strong influence of niobium admixture added to the lead–barium–zirconate–titanate ceramics of a chosen composition Ba/Zr/Ti 25/70/30 on grain structure, dielectric, and pyroelectric properties was confirmed. The Nb-modified ceramics exhibit classical relaxor ferroelectric behaviour similar to other complex lead perovskites such as lead–lanthanum–zirconate–titanate-type ceramics. Additional anomalies in ɛ′(T) curves in low frequency range were observed in the paraelectric phase for undoped ceramics. These anomalies and some disturbances in regularities typical for the relaxor ferroelectric behaviour in the vicinity of diffuse ferroelectric–paraelectric phase transition in undoped PBZT ceramics are eliminated by the Nb admixture. An attempt at a quantitative explanation is presented in the paper.     

Pb(Zn,Nb)(Sn,Nb)(Zr,Ti)O3材料的介电性能研究

通过分析PZSN系材料的介电温度与介电频率曲线 ,发现PZSN系材料没有明确的相变温度 ,相变属弥散型相变。 12 5K与 4M处的介电频率峰对应O -Ti-O与O -Zr -O的偶极子的空间取向的响应行为 ,在顺电相T >Tcav时这种偶极子是不存在的 ,说明它们的行为与相变有关     

In situ TEM observation on the ferroelectric-antiferroelectric transition in Pb(Nb,Zr,Sn,Ti)O3/ZnO

Ceramic composites of (1-x)Pb_0.99{Nb_0.02[(Zr_0.57Sn_0.43)_0.937Ti_0.063]_0.98}O₃ (PNZST)/xZnO were recently reported to exhibit exceptionally high pyroelectric coefficients near human body temperature due to the ferroelectric-antiferroelectric transition of the matrix grains. In the present work, a comparative study is conducted on two composites of x = 0.1 and 0.4 with in situ heating transmission electron microscopy (TEM). The results verify the presence of strain field in the PNZST grain adjacent to a ZnO particle and the stabilized ferroelectric phase at room temperature in the composite of x = 0.1. During heating, the ferroelectric matrix grain transforms to the antiferroelectric phase, contributing to the pyroelectric effect. In the composite of x = 0.4, high-angle annular dark-field imaging combined with energy-dispersive X-ray spectroscopy reveal the existence of both ZnO and Zn₂SnO₄. The formation of Zn₂SnO₄ indicates that Sn in the PNZST matrix grain is selectively extracted, and decomposition of the perovskite phase has taken place. The decomposition products in the form of fine particles are observed to facilitate the nucleation of the antiferroelectric phase and restrict the motion of the phase boundary during heating. The larger amount of ZnO and Zn₂SnO₄ and the decomposition of the PNZST perovskite phase are suggested to be responsible for the much lower pyroelectric coefficient in the x = 0.4 composite.     

Creating adjoining polymorphic phase transition (PPT) regions in ferroelectric (Ba,Sr)(Zr,Ti)O3 ceramics

In this work, we report the polymorphic phase transitions(PPT) in ferroelectric Ba_0.95Sr_0.05Zr_xTi_(1-x)O₃ (BSZT, x = 0.01–0.10) ceramics synthesized by using a solid-state reaction method. The doping elements and composition ratios were selected to create adjoining PPT phase boundaries near room temperature, hence to achieve a broadened peak of piezoelectric performance with respect to composition. The temperature-composition phase diagram was constructed and the effects of PPT on the electromechanical and ferroelectric properties of the ceramics were investigated. It was revealed that the two adjacent PPT regions at room temperature showed different characteristics in property enhancement. However, due to the proximity of the phase boundaries, Ba_0.95Sr_0.05Zr_xTi_(1-x)O₃ ceramics in a fairly broad range of compositions (0.02 ≤ x ≤ 0.07) showed excellent piezoelectric properties, including a large piezoelectric constant (312 pC/N ≤ d₃₃ ≤ 365 pC/N) and a high electromechanical coupling coefficient k_p (0.42 ≤ k_p ≤ 0.49).     

Microstructure and electric properties of Pr-doped Pb(Zr0.52Ti0.48)O3 ceramics

Improving the piezoelectric activity of lead zirconate titanate (PZT) ceramics is of great importance for practical applications. In this study, the influence of Pr³⁺ doping on the ferroelectric phase composition, microstructure, and electric properties on the A-site of (Pb_1-1.5xPr_x)(Zr_0.52Ti_0.48)O₃ is extensively investigated. A dense and fine microstructural sample is obtained with the introduction of Pr³⁺. The results show that the morphotropic phase boundary (MPB) moves to the rhombohedral phase region. The rhombohedral and tetragonal phases exhibit an ideal coexistence in the 4 mol.% Pr³⁺ doped (PPZT4) samples. Lead vacancy and the reduction of the potential energy barrier are considered to be the key mechanisms for donor doping, which is upheld by the Pr³⁺ doping. Combining the I-E hysteresis loops with the P-E hysteresis loops, it becomes apparent that both contribution maximums of the domain switching and residual polarisation are in PPZT4. Moreover, the thermal aging resistance of PZT is improved by doping, and the temperature stability is optimised from 83% in PZT to 96% in PPZT4. Hence, an appropriate amount of Pr³⁺ doping can effectively improve the piezoelectric activity of PZT ceramics in the MPB area and optimise the performance stability of the material under application temperatures.     

Hierarchical domain structures in (Pb,La)(Zr,Sn, Ti)O3 antiferroelectric ceramics

(Pb, La)(Zr, Sn, Ti)O₃ (PLZST) ceramic is one of the most prospective antiferroelectric (AFE) materials for variety of functional applications including energy storage and converter. Systematic structural investigation of domain structures should be of fundamental importance for understanding the structure-property relationship in AFE ceramics. In this study, the hierarchical domain structures and modulated structures correlated to the compositional variation in (Pb_0.97La_0.02) (Zr_0.50Sn_xTi_0.50-x)O₃ (x = 0.375, 0.45 and 0.50) were observed and investigated in details by transmission electron microscopy. The PLZST ceramics show exclusively incommensurate modulated structures (IMS) whose modulation period changed from 9.37 to 6.15 and to 4.04 with increasing of the x value. The hierarchical domain structures include, in decreasing scales, AFE domains, incommensurate domains and nanodomains. The elementary domains in PLZST ceramics are pinstriped nanodomains which were formed based on IMS configuration but by frequent modulation of IMS periodicity and formation of faults. Nanodomains accumulated and then dissociated into incommensurate domains and AFE domains successively. The presently revealed structural characteristics in antiferroelectric PLZST may stimulate future researches on the evolution of IMS-based hierarchical domains under external physical fields, e.g. thermal or electrical, and their correlation to the physical performance.     

Piezoelectric properties of Pb(Zr,Ti)O3-Pb(Ni,Nb)O3 ceramics and their application in energy harvesters

The piezoelectric properties of (1-x-y)PbZrO₃-xPbTiO₃-yPb(Ni_1/3Nb_2/3)O₃ ceramics were investigated. Specimens with a large Pb(Ni_1/3Nb_2/3)O₃ content, which have compositions close to the triple point, show small g₃₃ and d₃₃ × g₃₃ values because of their large ε^T₃₃/ε₀. These values increased with a decrease in y (amount of Pb(Ni_1/3Nb_2/3)O₃) and the specimen with x = 0.39 and y = 0.29 showed the largest g₃₃ of 43 × 10⁻³ V·m/N and d₃₃ × g₃₃ of 25.2 × 10⁻¹² m²/N. Cantilever-type energy harvesters were fabricated using specimens with 0.38 ≤ x ≤ 0.41 and y = 0.29. The output power densities of the energy harvesters were related to the d₃₁ × g₃₁ × k₃₁² value of the piezoelectric ceramics. The energy harvester fabricated using a specimen with x = 0.39 and y = 0.29, which has a maximum d₃₁ × g₃₁ × k₃₁² value, showed the maximum output power density of 1.01 mW/cm³.     

Diffuse phase transition and ferroelectric study of (Ba,Bi)(Ti,Cr)O3 ceramics

Lead-free perovskite type (Ba_0.94Bi_0.06)(Ti_0.94Cr_0.06)O₃ (BBTC) ceramics have been prepared by the conventional mixed oxide method. The XRD results showed that BBTC ceramics have single phase tetragonal symmetry with space group P4mm. Dielectric studies exhibited a diffuse phase transition characterized by a strong temperature and frequency dispersion of permittivity. The quantitative characterization based on empirical parameters (ΔT_m, γ, ΔT_relax, and ΔT_dif) confirmed its relaxor nature. The origin of relax ferroelectric behavior is caused by the polar nanoclusters, which were arose due to the heterovalent substitutions of Bi³⁺ and Cr³⁺ at Ba²⁺ and Ti⁴⁺ sites. The P–E loops obtained at the temperature quite above T_m supported the diffuse phase transition behavior of the samples.     

Energy storage and release properties of Sr-doped (Pb,La)(Zr,Sn,Ti)O3 antiferroelectric ceramics

Pb_0.94−xLa_0.04Sr_x[(Zr_0.6Sn_0.4)_0.84Ti_0.16]O₃ (x=0,0.02,0.04,0.06) antiferroelectric ceramics were fabricated via conventional solid-state reaction. The increase of Sr content enhanced the stability of antiferroelectric phase, which resulted in the rise of phase transition fields and energy density. When x=0.06, the releasable energy density was 1.52 J/cm³ and the efficiency was 93.3% under 129 kV/cm. The pulsed discharge current was also measured to evaluate the energy release properties. Under 129 kV/cm, the obtained current density could be as high as 165.5 A/cm². The pulsed discharge energy density was 1.21 J/cm³ and 90% of that could be released in less than 200 ns. The high energy density, high efficiency and fast energy release time indicate that the obtained AFE ceramics are very promising for pulsed power capacitors.     

Superior energy-storage properties in (Pb,La)(Zr,Sn,Ti)O3 antiferroelectric ceramics with appropriate La content

Antiferroelectric (AFE) ceramics based on Pb(Zr,Sn,Ti)O₃ (PZST) have shown great potential for applications in pulsed power capacitors because of their fast charge-discharge rates (on the order of nanoseconds). However, to date, it has been proven very difficult to simultaneously obtain large recoverable energy densities W_re and high energy efficiencies η in one type of ceramic, which limits the range of applications of these materials. Addressing this problem requires the development of ceramic materials that simultaneously offer a large ferroelectric-antiferroelectric (FE-AFE) phase-switching electric field E_A, high electric breakdown strength E_b, and narrow polarization-electric field (P-E) hysteresis loops. In this work, via doping of La³⁺ into (Pb_1-1.5xLa_x)(Zr_0.5Sn_0.43Ti_0.07)O₃ AFE ceramics, large E_A and E_b due to respectively enhanced AFE phase stability and reduced electric conductivity, and slimmer hysteresis loops resulting from the appearance of the relaxor AFE state, are successfully obtained, and thus leading to great improvement of the W_re and η. The most superior energy storage properties are obtained in the 3?mol% La³⁺-doped (Pb_1-1.5xLa_x)(Zr_0.5Sn_0.43Ti_0.07)O₃ AFE ceramic, which simultaneously exhibits at room temperature a large W_re of 4.2?J/cm³ and a high η of 78%, being respectively 2.9 and 1.56 times those of (Pb_1-1.5xLa_x)(Zr_0.5Sn_0.43Ti_0.07)O₃ AFE ceramics with x?=?0 (W_re?=?1.45?J/cm³, η?=?50%) and also being superior to many previously published results. Besides, both W_re and η change very little in the temperature range of 25–125?°C. The large W_re, high η, and their good temperature stability make the Pb_0.955La_0.03(Zr_0.5Sn_0.43Ti_0.07)O₃ AFE ceramic attractive for preparing high pulsed power capacitors useable in various conditions.     

Homogenization of Pb(Zr,Ti)O3 by use of molten phase

A method for a homogenization of Pb(Zr,Ti)O₃(PZT) was developed. Powders of PbO and TiO₂ were added into a powder of PZT prepared by the ordinary method. This mixture was heated above the melting point of PbO for several periods of time. PbO and TiO₂ formed a molten phase. After the heat treatment, it was quenched. PbO phase in the sample was removed by dissolving with acetic acid. The chemical homogeneity of the PZT phase was figured out using βcosθ vs. sinθ plots. This analysis showed that the chemical homogeneity in the PZT phase was improved very quickly.     

Effect of Ba Content on the Stress Sensitivity of the Antiferroelectric to Ferroelectric Phase Transition in (Pb,La,Ba,)(Zr,Sn,Ti)O3 Ceramics

The effect of Ba content on the stress sensitivity of the antiferroelectric to ferroelectric phase transition in (Pb_0.94?xLa_0.04Ba_x)[(Zr_0.60Sn_0.40)_0.84Ti_0.16]O₃ ceramics is investigated through monitoring electric field‐induced polarization and longitudinal strain under compressive prestresses. It is found that incorporation of Ba significantly suppresses the stress sensitivity of the phase transition, as manifested by slight decreases under prestresses up to 100 MPa in the maximum polarization (P_m) and longitudinal strain (x_m). The energy storage density is even increased under the mechanical confinement in compositions x = 0.02 and 0.04. X‐ray diffraction, transmission electron microscopy, and dielectric measurements indicate that the suppressed stress sensitivity is associated with the disruption of micrometersized antiferroelectric domains into nanodomains and the transition from antiferroelectric to relaxor behavior.     

Giant field-induced strain in Nb2O5-modified (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics

Lead-free piezoceramics (Na_(1+x)/2Bi_(1-x)/2)_0.94Ba_0.06Ti_1-xNb_xO₃ (BTN100x) were prepared using conventional solid-state reaction method. The structures, field- induced strain, AC impedance of sintered ceramics were investigated. The pure perovskite solid solution BTN3 exhibited giant electric-field-induced strain of 0.478% under an electric field of 70 kV/cm at ambient temperature, meanwhile, the normalized strain (S_max/E_max) reached up to 654 pm/V. The giant strain was insensitive to temperature and exhibited excellent fatigue resistance performance within 10⁶ switching cycles, making it a promising candidate material for actuator applications. Complex AC impedance spectra confirmed the contribution of grain effect to resistivity behavior. The field-induced giant strain was attributed to the phase transition between ferroelectrics and relaxor ferroelectrics induced by introducing Nb₂O₅.     

High piezoelectricity in CuO-modified Ba(Ti0.90Sn0.10)O3 lead-free ceramics with modulated phase structure

High piezoelectricity was achieved in Ba(Ti_0.90Sn_0.10)O₃ lead-free ceramics by optimizing CuO addition and sintering temperature. The phase structure of 1.0 mol% CuO-doped Ba(Ti_0.90Sn_0.10)O₃ ceramic is coexisting rhombohedral and tetragonal phases as sintered at 1300 °C. The coexistence of rhombohedral, tetragonal and orthorhombic phases appears in 1.0 mol% CuO-doped Ba(Ti_0.90Sn_0.10)O₃ ceramics as sintered at 1350–1450 °C, which leads to highly enhanced d₃₃ up to 650pC/N. This work demonstrates that high piezoelectric property (d₃₃ = 650pC/N) can be obtained in BaTiO₃-based lead-free piezoceramics with a simple composition modification by modulating phase structures, which also indicates that Ba(Ti,Sn)O₃ is a promising candidate to replace the lead-based piezoceramics.     

Influence of Ca substitution on microstructure and electrical properties of Ba(Zr,Ti)O3 ceramics

In the present work, lead-free (Ba_1?xCa_x)(Zr_0.04Ti_0.96)O₃ (x=0.00–0.09) ceramics were fabricated via a solid-state reaction method. The microstructure and electrical properties of the ceramics were investigated. The microstructure of the BCZT ceramics showed a core shell structure at compositions of x=0.03 and 0.06. The substitution of small amount of Ba²⁺ by Ca²⁺ resulted in an improvement of the piezoelectric, dielectric and ferroelectric properties of the ceramics. The orthorhombic–tetragonal phase transition was found in the composition of x≤0.03. Piezoelectric coefficient of d₃₃～392 pC/N and lowest E_c～3.3 kV/cm with highest P_r～14.1 μC/cm² were obtained for the composition of x=0.03 while its Curie temperature (T_C) was as high as 125 °C. However, the ferroelectric to paraelectric transition temperature had slightly shifted towards room temperature with increasing Ca²⁺ concentration.     

Microstructure and dielectric properties of perovskite-structured high-entropy ceramics of Pb(Zr0.25Ti0.25Sn0.25Hf0.25)O3

A dielectric high-entropy ceramic with a composition of Pb(Zr_0.25Ti_0.25Sn_0.25Hf_0.25)O₃ was designed through B-site doping, and then prepared by solid phase reaction method combined with conventional sintering in air for 3 h at 1200 ^°C, 1250 ^°C and 1300 ^°C, respectively. All the high-entropy ceramics of Pb(Zr_0.25Ti_0.25Sn_0.25Hf_0.25)O₃ possess a perovskite structure with uniform elemental distribution and their average grain size falls within the range of 3.19–5.5 μm. For the sample sintered at 1250 ^°C, the dielectric loss is less than 0.07 in the testing frequency of 1 kHz∼1 MHz in 30–350 ^°C, and the dielectric constant reaches a peak of 14356 at about 270 ^°C at 1 kHz. At room temperature, the remnant polarization P_r reaches 28.8 μC/cm². The results demonstrate that the high-entropy ceramic of Pb(Zr_0.25Ti_0.25Sn_0.25Hf_0.25)O₃ has great potentials in the dielectric and ferroelectric field.     

Dielectric and pyroelectric properties of Nb-doped Pb(Zr0.92Ti0.08)O3 ceramics

Dielectric and pyroelectric characteristics and changes of electric conductivity were investigated for Nb₂O₅-doped Pb(Zr_0.92Ti_0.08)O₃ ceramics. The influence of this dopant on the ceramics microstructure was also studied. Correlation between the investigated electric characteristics and grain structure was confirmed. Some progress in understanding the influence of Nb-dopant was reached in this way.     

Enhancing pyroelectric properties in (Pb1–1.5xLax)(Zr0.86Ti0.14)O3 ceramics through composition modulated phase transition

Currently, there is an urgent need of extraordinary comprehensive pyroelectric materials for the wide application in detectors and energy harvesters. In this study, the (Pb_1–1.5xLa_x)(Zr_0.86Ti_0.14)O₃ (abbreviated as PLZT, x?=?0.02, 0.03, 0.04 and 0.05) ceramics located in ferroelectric-antiferroelectric (FE-AFE) phase boundary were designed and synthesized by using conventional solid-state reaction method. The microstructures, phase structures, dielectric, ferroelectric, thermal depolarization and pyroelectric properties of the PLZT ceramics with different La content were investigated thoroughly. The XRD results show that the PLZT ceramics change from FE phase to AFE phase with increasing La content. The significant improvement of pyroelectric coefficient $p$ and figures of merit (FOMs) are achieved in the PLZT ceramics with the increase in La content because of the increased metastable ferroelectric phase under the application of electric field. The (Pb_0.955La_0.03)(Zr_0.86Ti_0.14)O₃ (x?=?0.03) ceramic exhibits not only high $p$ of $5.2\times {10}^{?8}\mathrm{C}/{\mathrm{cm}}^2\mathrm{K}$ and high depolarization temperature (T_d) of 179?℃ but also excellent FOMs with $F_i=2.2\times {10}^{?10}\mathrm{m}/\mathrm{V}$, $F_v=5.0\times {10}^{?2}{\mathrm{m}}^2/\mathrm{C}$, and $F_d=3.47\times {10}^{?5}{\mathit{Pa}}^{?1/2}$. In addition, the highest $p$ of $6.8\times {10}^{?8}\mathrm{C}/{\mathrm{cm}}^2\mathrm{K}$ is achieved in (Pb_0.94La_0.04)(Zr_0.86Ti_0.14)O₃ (x?=?0.04) ceramic. These results demonstrate that the PLZT ceramics of x?=?0.03 and 0.04 are promising candidates for pyroelectric applications.     

Processing and dielectric properties of (Pb,Bi)(Mg,Nb,Ti)O3 ceramics

Powders of the Pb(Mg_1/3Nb_2/3)O₃–Bi(Mg_2/3Nb_1/3)O₃ (PMN–BMN) system with PbTiO₃ (PT) substitution levels of 20 and 30 mol% were prepared by a B-site precursor method. Phase development as well as dielectric properties were examined. Two major phases, i.e., MgNb₂O₆ and [(Mg_1/3Nb_2/3)_1/2Ti_1/2]O₂ (with small fractions of Mg₄Nb₂O₉), developed in the B-site precursor compositions, whereas only monophasic perovskite formed after the addition of PbO/Bi₂O₃. Maximum dielectric constant values of the two systems decreased rapidly with increasing BMN concentration, but corresponding temperatures were lowest at intermediate compositions.