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     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Piezoelectric softening by Nb substitution in (Ba,Pb)ZrO3 ceramics

Donor doping is commonly applied for softening of the piezoelectric and dielectric properties and facilitation of polarization switching in the ubiquitous Pb(Zr,Ti)O₃ [PZT] ceramics. The origin of the donor‐dopant effects is not entirely clear. (Pb,Ba)ZrO₃ [PBZ] is a related ferroelectric material, its perovskite A‐site being partially occupied by the larger Ba⁺² cation, less prone to evaporation than Pb⁺², and the B‐site is occupied entirely by the valency‐stable Zr⁺⁴. Here we report on our studies of Nb⁺⁵ doping effects in (Pb,Ba)ZrO₃. Similarly, to past observations on La⁺³ and Nb⁺⁵ doped PZT, we find a strong reduction in relative density of PBZ when the doping is <0.5 atomic %. This is accompanied by lattice parameter reduction, enhanced PbO loss, smaller grain size and deterioration of dielectric, piezoelectric and polarization switching properties, the latter being opposite of expected softening effect. All those observations can be interpreted in terms of the Nb entering A‐site at small concentrations. This is supported by ab‐inito calculations and analysis of the possible defect reaction equations. The structure and microstructure of PBZ with Nb>0.2% are consistent with Nb⁺⁵ entering the B‐site and softening effects are observed. The study supports the scenario of hardening due to domain walls pinning by V_Pb‐V_O divacancies and softening upon decrease in their concentration.     

Pb(Zr,Sn,Ti)O3中组份变化对反铁电-铁电相变的影响

探讨了掺铌Ｐｂ（Ｚｒ,Ｓｎ,Ｔｉ）Ｏ３反铁电陶瓷中,组份变化对晶体结构及电场诱导反铁电－铁电相变性能的影响,分析结果表明;在Ｐｂ０．９９Ｎｂ０．０２〖（Ｚｒ１－ｘＳｎｘ）１－７Ｔｉｙ〗０．９８Ｏ３反铁电陶瓷中,ｙ增加,反铁电四方相晶轴比减小,增加晶胞体积,诱导反铁电－铁电相变的开关电场强度降低,ｘ增加,反铁电四放相的晶轴比ａ／ｃ铁电相变的反铁电相区。     

Field induced metastable ferroelectric phase in Pb0.97La0.03(Zr0.90Ti0.10)0.9925O3 ceramics

Pb_0.97La_0.03(Zr_0.9Ti_0.1)_0.9925O₃ (PLZT 3/90/10) ceramics prepared by solid-state reaction with the compositions near the antiferroelectric/ferroelectric (FE/AFE) phase boundary were studied. From the polarization–electric field P(E) dependence and ex situ X-ray study, an irreversible electric field induced AFE-to-FE phase transition is verified at room temperature. Dielectric and in situ temperature dependent X-ray analysis evidence that the phase transition sequence in PLZT 3/90/10-based ceramics can be readily altered by poling. A first order antiferroelectric-paraelectric (AFE-to-PE) transition occurred at?～190 °C in virgin sample and at?～180 °C in poled sample. In addition, a FE-to-AFE transition occurs in the poled ceramic at much lower temperatures (～120 °C) with respect to the Curie range (～190 °C). The temperature-induced FE-to-AFE transition is diffuse and takes place in a broad temperature range of 72–135 °C. The recovery of AFE is accompanied by an enhancement in the piezoelectric properties.     

Local structure study of phase transition behavior in Ba(Ti,Sn)O3 perovskite by X-ray absorption fine structure

In this work, BaTi_1−xSn_xO₃ (BST) powders (x=0–0.95) were synthesized by a conventional mixed-oxide method. The phase information was investigated by a combination of X-ray diffraction and X-ray absorption spectroscopy techniques. The XRD measurements indicated the global phase transition from tetragonal to cubic perovskite structure. From the synchrotron X-ray Absorption Near-Edge Structure (XANES) measurements at the Ti K-edge and Sn L₃-edge, it was seen that an increase of Sn content in BaTiO₃ affected the phase transition behavior and local structure of BST. In addition, the local structure of Ba(Ti,Sn)O₃ materials were experimentally determined and compared with that obtained from the simulation. The local structure obtained from the XANES technique provided additional structural information unavailable from XRD investigation. Finally, the phase transition behavior from relaxor ferroelectric to polar cluster in BST system was discussed and attributed mainly to the change in the local structure.     

Microstructure and electrical properties of (Pb0.87Ba0.1La0.02)(Zr0.68Sn0.24Ti0.08)O3 anti-ferroelectric ceramics fabricated by the hot-press sintering method

(Pb_0.87Ba_0.1La_0.02)(Zr_0.68Sn_0.24Ti_0.08)O₃ anti-ferroelectric ceramics with various amounts of excess PbO have been fabricated by the conventional solid-state reaction process and the hot-press sintering method, and the dependence of microstructure, ferroelectric and dielectric properties on sintering approaches and lead volatilization conditions has been studied. When an appropriate quantity of excess PbO is added, the lead volatilization effect can be compensated and the content of pyrochlore phase is decreased. Hot-pressed anti-ferroelectric ceramics exhibit much higher densities than conventionally sintered samples. The spontaneous polarization and maximum dielectric constant of the AFE ceramics decrease when the hot-press sintering method is used. The dielectric loss can be obviously reduced by using the hot-press sintering method and adding a proper amount of excess PbO. The systemic investigation of the lead volatilization effect and the hot-press sintering method will contribute to the development of high properties of anti-ferroelectric ceramics in practical applications.     

Electronic structure and transport properties of sol-gel-derived high-entropy Ba(Zr0.2Sn0.2Ti0.2Hf0.2Nb0.2)O3 thin films

High-entropy perovskite thin films, as the prototypical representative of the high-entropy oxides with novel electrical and magnetic features, have recently attracted great attention. Here, we reported the electronic structure and charge transport properties of sol-gel-derived high-entropy Ba(Zr_0.2Sn_0.2Ti_0.2Hf_0.2Nb_0.2)O₃ thin films annealed at various temperatures. By means of X-ray photoelectron spectroscopy and absorption spectrum, it is found that the conduction-band-minimum shifts downward and the valence-band-maximum shifts upward with the increase of annealing temperature, leading to the narrowed band gap. Electrical resistance measurements confirmed a semiconductor-like behavior for all the thin films. Two charge transport mechanisms, i.e., the thermally-activated transport mechanism at high temperatures and the activation-less transport mechanism at low temperatures, are identified by a self-consistent analysis method. These findings provide a critical insight into the electronic band structure and charge transport behavior of Ba(Zr_0.2Sn_0.2Ti_0.2Hf_0.2Nb_0.2)O₃, validating it as a compelling high-entropy oxide material for future electronic/energy-related technologies.     

Electrocaloric Effect in Ba(Zr,Ti)O3–(Ba,Ca)TiO3 Ceramics Measured Directly

In this paper, we report on studies of the electrocaloric (EC) effect in lead‐free (1?x)Ba(Zr_0.2Ti_0.8)O₃–x(Ba_0.7Ca_0.3)TiO₃ ceramics with compositions range between 0.32 ≤ x ≤ 0.45. The EC effect was measured directly using a modified differential scanning calorimeter. The maximum EC temperature change, ΔT_direct = 0.33 K under an electric field of 2 kV/mm, was observed for the composition with x = 0.32 at ~63°C. We found that the EC effect peaks not only around the Curie temperature but also at the transition between the ferroelectric phases with different symmetries. A strong discrepancy observed between the results of the direct measurements and indirect estimations points out that using Maxwell's equations is invalid for the thermodynamic nonequilibrium conditions that accompany only partial (incomplete) poling of ceramics. We also observe a nonlinearity of the EC effect above the Curie temperature and in the temperature range corresponding to the tetragonal ferroelectric phase.     

Enhanced thermal stability of piezoelectricity in lead-free (Ba,Ca)(Ti,Zr)O3 systems through tailoring phase transition behavior

Good thermal stability in lead-free BaTiO₃ ceramics is important for their applications above room temperature. In this study, thermal stable piezoelectricity in lead-free (Ba,Ca)(Ti,Zr)O₃ ceramics was enhanced by tailoring their phase transition behaviors. Comparison between (1-x)Ba(Ti_0.8Zr_0.2)O₃-x(Ba_0.65Ca_0.35)TiO₃ and (1-y)Ba(Ti_0.8Zr_0.2)O₃-y(Ba_0.95Ca_0.05)TiO₃ revealed that latter system at y?=?0.80 had much better thermal stable piezoelectric coefficient than the former at x?=?0.45. Both systems crystalized in tetragonal to orthorhombic phase boundary at room temperature. The phase transition temperature and degree of diffusion were adjusted by Ca and Zr ions contents and demonstrated great influence on temperature dependent dielectric permittivity, hysteresis loops, and in-situ domain structures. The improved thermal stability of (1-y)Ba(Ti_0.8Zr_0.2)O₃-y(Ba_0.95Ca_0.05)TiO₃ prepared at y?=?0.80 was linked to its higher paraelectric to ferroelectric phase transition temperature (T_m?=?115.7?°C) and less degree of diffusion (degree of diffusion constant γ?=?1.35). By comparison, (1-x)Ba(Ti_0.8Zr_0.2)O₃-x(Ba_0.65Ca_0.35)TiO₃ prepared at x?=?0.45 revealed T_m?=?81.3?°C and γ?=?1.65. Overall, these findings look promising for future stimulation of phase transition behaviors and design of piezoelectric materials with good thermal stabilities.     

Porosity‐dependent properties of Nb‐doped Pb(Zr,Ti)O3 ceramics

In the present work, it is shown how the controlled porosity can be exploited to obtain a compromise between a reduced permittivity down to a few hundreds and maintaining a high tunability level as in the dense material, to fulfill requirements for tunable applications. Nb‐doped Pb(Zr,Ti)O₃ ceramics with porosity in the range 5%‐30% have been prepared by direct sintering method. X‐ray diffraction analysis and Rietveld refinement indicated a co‐existence of tetragonal and monoclinic phases in the porous ceramics. Dielectric properties revealed a gradual reduction in permittivity when increasing the porosity level, while maintaining low dielectric losses below 3%. The ferroelectric switching behavior is also influenced by the porosity level: a continuous reduction in the saturation and remnant polarization is observed with increasing porosity. The nonlinear dielectric properties of all the investigated ceramics preserve a high level of tunability in comparison with one of the dense material, irrespective of the porosity level, while zero field permittivity was decreased below 1000. An optimum behavior is found for the ceramic sample with 25% porosity, which shows a high tunability, smaller losses, and moderate dielectric constant (ε ~600).