Enhanced thermal stability and large piezoelectric properties of Sm-doped Pb(Sc1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 multifunctional ceramics

Journal of Materials Science - The crystal structure, electric properties, thermal stability and optical properties of Sm-doped 0.15Pb(Sc1/2Nb1/2)O3–0.50Pb(Mg1/3Nb2/3)O3–0.35PbTiO3...     

Dielectric and electromechanical properties of Mn-doped 0.2875 Pb(Mg1/3Nb2/3)O3–0.2875 Pb(Yb1/2Nb1/2)O3–0.425 PbTiO3 ceramics

In this study, 0.2875 Pb(Mg_1/3Nb_2/3)O₃–0.2875 Pb(Yb_1/2Nb_1/2)O₃–0.425 PbTiO₃ (0.2875PMN–0.2875PYbN–0.425PT) ternary ceramic composition was doped with 1 mol% MnCO₃ in order to induce hard character for potential high-power applications. Dense 0.2875PMN–0.2875PYbN–0.425PT ceramics with 1 mol% MnCO₃ addition were fabricated after sintering at 1100 °C. ε _r = 1728, tanδ = 0.35 %, d ₃₃ = 320 pC/N, d ₃₁ = ?103 pC/N, Q _m = 467, k _p = 0.40, k ₃₁ = 0.24, k ₃₃ = 0.49, and T _c = 280 °C were measured for Mn-doped ceramics. However, undoped ceramics had ε _r = 2380, tanδ = 1.95 %, d ₃₃ = 433 pC/N, d ₃₁ = ?145 pC/N, Q _m = 60, k _p = 0.43, k ₃₁ = 0.27, k ₃₃ = 0.48, and T _c = 285 °C. Acceptor Mn²⁺/Mn³⁺ ions presumably substituted B-site ions in the perovskite structure and formed defect dipole pairs. The electrically “hard” character was induced as a result of the domain wall pinning due to the existing defect pairs. Particularly, increasing Q _m from 60 to 467 and decreasing tanδ from 1.95 to 0.35 % after Mn doping showed that Mn-doped 0.2875PMN–0.2875PYbN–0.425PT ceramics with “hard” character are potential candidates for high-power projector and transducer applications.     

Sintering and electrical properties of Nb5+ doped 0.63Bi(Mg1/2Ti1/2)O3–0.37PbTiO3 piezoelectric ceramics

Nb⁵⁺ doped 0.63Bi(Mg_1/2Ti_1/2)O₃–0.37PbTiO₃ (0.63BMT–0.37PT?+?xNb⁵⁺) ceramics have been fabricated by means of citrate sol–gel method and ordinary sintering. Effects of Nb⁵⁺ doping on the densification and various electrical properties were studied. The results indicated that the addition of a small amount of Nb⁵⁺ gradually changes the crystal structure from a typical rhombohedral-tetragonal coexisted structure to a nearly pure rhombohedral structure. A slight amount of secondary phases start to appear as the doping content of Nb⁵⁺ is more than 1.5?mol%, indicating that the solubility limit of Nb⁵⁺ in the matrix composition is reached. Moreover, electrical properties of the sintered ceramics were obviously changed based on the effect of densification and ionic substitution. 0.63BMT–0.37PT?+?0.005Nb⁵⁺ ceramics sintered at 1,020?°C exhibit optimum properties of piezoelectric constant d₃₃?~?245 pC/N, planar electromechanical coupling factor k_p?~?30?%, $ \varepsilon_{33}^{\text{T}} /\varepsilon_{\text{o}} $ ?~?1,220, and T_c?~?460?°C.     

Dielectric and Piezoelectric Properties of Pb(Mg1/3Nb2/3)O3–PbTiO3–Pb(Mg1/2W1/2)O3 Ceramics

Data are presented on the phase composition, crystal structure, microstructure, and dielectric and piezoelectric properties of (1 – y)[(1 – x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃]–yPb(Mg_1/2W_1/2)O₃ (x = 0.30–0.36; y = 0, 0.05, 0.10) ceramics. It is shown that the use of fine-particle magnesia as a starting reagent ensures the formation of single-phase materials. The ceramics with a rhombohedral structure are found to exhibit relaxor behavior. Increasing the content of the Pb(Mg_1/2W_1/2)O₃ perovskite leads to ordering of the domain structure of poled ceramics and increases their piezoelectric charge coefficient d ₃₁ and the width of their phase transitions.     

Effect of La-doping content on the dielectric and ferroelectric properties of 0.88Pb(Mg1/3Nb2/3)O3–0.12PbTiO3 ceramics

Dense relaxor ferroelectric 0.88Pb(Mg_1/3Nb_2/3)O₃–0.12PbTiO₃ (0.88PMN–0.12PT) ceramics with different La-doping contents (0, 1, 2 and 4 at.%) were sintered by using powders synthesized via a solid-state reaction route. The effects of La doping on the microstructures and electric properties of the 0.88PMN–0.12PT ceramics were investigated. It was found that the average grain size, remanent polarization P _r, coercive field E _c, Curie temperature T _c and leakage-current density J of the ferroelectric ceramics decrease significantly with increasing La doping content. The decrease in P _r, E _c and T _c can be understood in term of the fact that the substitution of Pb²⁺ ions by La³⁺ ions suppresses the long-range coupling of BO₆ octahedrons, while the abatement in J can be explained according to the reduction of oxygen vacancies caused by La doping. By fitting the J–E curves, the conduction mechanism of the 0.88PMN–0.12PT ceramics is confirmed to be Ohmic conduction generated from oxygen vacancies. The dielectric and ferroelectric properties of 0.88PMN–0.12PT ceramics are tunable with manipulating the La doping content.     

Investigation of phase diagram and electrical properties of xPb(Mg1/3Nb2/3)O3–(1 − x)Pb(Zr0.4Ti0.6)O3 ceramics

Ceramics in PMN–PZT system with formula xPb(Mg_1/3Nb_2/3)O₃–(1 ? x)Pb(Zr_0.4Ti_0.6)O₃ (where x = 0.32, 0.35, 0.38, 0.41) were prepared by the conventional oxide-mixed method. The phase diagram, composition dependent ferroelectric, dielectric, field-induced strain and piezoelectric properties were systematically investigated. X-ray diffraction analysis indicated that as-prepared ceramics were of pure perovskite phase and the possible morphotropic phase boundary (MPB) between the tetragonal and pseudo-cubic phase compositions were located near the PMN content of x = 0.38, confirmed by their corresponding ferroelectric, dielectric, field-induced strain and piezoelectric properties. The composition with x = 0.38 possessed the optimum electrical properties since its composition locate close to the MPB where exist multiple polarization directions facilitates domain reorientation and consequently enables the superior electrical properties. The room temperature dielectric permittivity ε _r , tangent loss tan δ, piezoelectric coefficient d ₃₃, electromechanical coupling factor kp, remnant polarization P _r , hysteresis loop squareness R _sq and longitudinal strain of 0.38PMN–0.62PZT ceramics are 2441, 2.08 %, 662 pC/N, 63.5 %, 37.2 μC/cm², 1.51 and 1.9 ‰, respectively, which mean it has a great promise for actuator applications.     

Low-temperature sintering and piezoelectric properties of Pb(Fe2/3W1/3)O3–added Pb(Zn1/3Nb2/3)O3–Pb(Ni1/3Nb2/3)O3–Pb(Zr,Ti)O3 ceramics

Low-temperature sintering of (a–x)Pb(Zr_0.48Ti_0.52)O₃–bPb(Ni_1/3Nb_2/3) O₃–cPb(Zn_1/3Nb_2/3)O₃–xPb(Fe_2/3W_1/3)O₃ (a + b + c + x = 1, 0.06 ≤ x ≤ 0.10) ceramics were prepared through two-step synthesis process using perovskites-structured ferroelectric materials Pb(Fe_2/3W_1/3)O₃ (PFW) as a sintering aid. The effects of PFW content on the densification, microstructure, phase structure, dielectric and piezoelectric properties of the ceramics were investigated. The sintering temperature was reduced from 1,180 °C (without PFW addition) to 940 °C when the material was PFW-doped. PFW-doping increased the sintered density and the average grain size of PFW–PNN–PZN–lead zirconate titanate ceramics. The ceramics sintered at 940 °C for 4 h with x = 0.08 exhibited favorable properties, which were listed as follows: d₃₃ = 496pC/N, εT 33/ε₀ = 3,119, tanδ = 2.1 % and Curie temperature = 242 °C. These values indicated that the newly developed composition might be suitable for multilayer piezoelectric devices application.     

Processing and electrical properties of (1 − x)[(1 − y)(Pb(Mg1/3Nb2/3)O3)–y(Pb(Yb1/2Nb1/2)O3)]–xPbTiO3 ceramics

Ferroelectric ceramics in the vicinity of morphotropic phase boundary (MPB) with compositions represented as (1 ? x)[(1 ? y)(Pb(Mg_1/3Nb_2/3)O₃)–y(Pb(Yb_1/2Nb_1/2)O₃)]–xPbTiO₃ were prepared by solid state reaction. The addition of PYbN to PMN–PT decreased the sintering temperature from 1200 °C (y = 0.25) to 1000 °C (y = 0.75). The PT content, where the MPB was observed, increased with the PYbN addition. A remanent polarization value of 28.5 µC/cm² and a coercive field value of 11 kV/cm were measured from 0.62[0.25PMN–0.75PYbN]–0.38PT ceramics, which were close to the ones measured from PMN–0.32PT ceramics. In addition, the Curie temperature was found to increase with PYbN additions.     

Effect of micro-region heterogeneity on phase structure and dielectric properties in Pb(Zn1/3Nb2/3)O3–PbTiO3–BaTiO3 ceramics

The phase structures of PZN-PT-BT ceramics under different synthesizing steps and thermal treatment were investigated. Although the calcinated powders (C.T. = 900 °C) of the compositions in tetragonal area exhibit pure tetragonal structure, the phase structures of the ceramics sintering at higher temperatures (S.T. 1080 °C) are the mixtures of tetragonal and rhombohedral. The content of tetragonal phase in PZN-PT-BT ceramics decreases further after the specimens are annealed. Dielectric and ferroelectric properties were studied. The annealed ceramics have higher average phase transition temperatures, lower frequency dispersions, lower dissipation factors and larger aging rates. The maximum of the dielectric constant and the spontaneous polarization at room temperature are almost unaffected by annealing process. The concept of nano-phase separation is assumed to explain the experimental results.     

High and tunable piezoelectric coefficients in 0.675Pb(Mg⅓Nb⅔)O3–0.325PbTiO3 ceramics

In this study, ceramic samples with composition 0.675Pb(Mg_?Nb_?)O₃–0.325PbTiO₃ were tested and assessed in terms of piezoelectric applications. This material showed relaxor ferroelectric behavior at temperatures around the ferro-paraelectric phase transition. In this temperature region, the material also had a high real dielectric permittivity, which fell slightly with the application of an electric field between 0 and 1 kV/mm. Consequently, high effective piezoelectric coefficients were observed for this material, which were found to be almost linearly tunable with electric fields between 1 and 3 kV/mm. Hence, the material studied here appears to be a promising candidate for the manufacture of certain piezoelectric devices.     

Microstructure and microwave dielectric properties of Ba(Mg1/3Nb2/3)O3–MgO composite ceramics with nano-silica added

Ba(Mg_1/3Nb_2/3)O₃–MgO composite ceramics were prepared by solid-phase method. The ceramic exhibited the 1:2 ordered structure. By adding a proper amount of MgO, the permittivity decreased rapidly compared with other Ba(Mg_1/3Nb_2/3)O₃-based ceramics. The Q?×?f values of the samples were greatly improved by nano-silica. Raman spectra showed that the permittivity and Q?×?f value showed a strong correlation with Raman shift and full width at half maximum of the A_1g(O) phonon mode, respectively. The Raman shift of A_1g(O) was consistent with the variation trend of permittivity. And the full width at half maximum of the A_1g(O) phonon mode had a negative correlation with the Q?×?f value. The results showed that upon adding 1.5 wt% nano-silica to the ceramics, the ceramics sintered at 1550 °C for 5 h had the lowest Raman shift and the narrowest full width at half maximum, achieving the best microwave dielectric properties: ε_r?=?22.22, Q?×?f?=?80,436 GHz, τ_f?=?–?5.89 ppm/°C.

     

Electrocaloric properties of (1 − x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 ferroelectric ceramics near room temperature

Electrocaloric effects of (1 − x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃ [abbreviated as (1 − x)PMN–xPT] ferroelectric ceramics with x being, 0.08, 0.10, and 0.25, respectively, were measured near room temperature, and the origins of the electrocaloric effects of these ceramics were discussed. It was found that these ceramics possess large electrocaloric effect with ΔT being, more than 1 K under an electric field of 1.5 kV mm⁻¹ in a wide temperature range (more than 10 K) near room temperature, and this effect is due to both of the electrocaloric effect resulting from the electric field induced first-order phase transition and the linear electrocaloric effect. It is expected that these ceramics could be used for multi-stage cascade ferroelectric refrigeration near room temperature.     

Temperature-dependent electrical properties of 0.5Pb(Ni1/3Nb2/3)O3–(0.5 − x)PbTiO3–xPbZrO3 piezoceramics near the morphotropic phase boundary

0.5Pb(Ni_1/3Nb_2/3)O₃–(0.5 ? x)PbTiO₃–xPbZrO₃ (x = 0.10–0.20) polycrystalline ceramics were fabricated by solid-state reaction method. The phase structures, microstructure and temperature dependence of the electrical properties were investigated in detail. Both X-ray diffraction and Raman spectroscopy results indicated that the morphotropic phase boundary (MPB) separating tetragonal from rhombohedral phases located around the region with x = 0.14–0.16. Well-saturated ferroelectric P–E loops were obtained for all compositions and the compositions near MPB possessed the relative large remnant polarization P _r  ~ 24 μC/cm² and low coercive field E _c  ~ 5 kV/cm. High performance of electric-induced-strain property with $ d_{33}^{*} $ (S _max /E _max ) up to 1,140 pm/V could be achieved in the composition with x = 0.15. When the content of PbZrO₃ was 14 mol%, the ceramics showed slightly lowered piezoelectric coefficient $ d_{33}^{*} $ of 898 pm/V. But excellent temperature stability of piezoelectric property was exhibited that the $ d_{33}^{*} $ changed <10 % when the temperature increased from room temperature to 120 °C. The piezoelectric property of this solid solution makes it promising for application in multilayer piezoactuators.     

Preparation and dielectric properties of Pb[(Zn1/3Ta2/3)0.8−x(Mg1/3Nb2/3)xTi0.2]O3 ceramics

A PbTiO₃ component of 20 mol% was substituted into a Pb[(Zn_1/3Ta_2/3),(Mg_1/3Nb_2/3)]O₃ system to promote the perovskite formation, especially at Pb(Zn_1/3Ta_2/3)O₃-rich compositions. Perovskite formation yields after the heat treatments were determined by X-ray diffraction. Weak-field dielectric properties of the ceramics were investigated as functions of temperature and frequency. A quite high value of the maximum dielectric constant (37,900 at 1 kHz) was realized, whereas the dielectric maximum temperatures of the entire compositions stayed nearly constant. Microstructure developments in the sintered ceramics were also examined.     

Effect of La on piezoelectric properties of Pb(Ni1/3Sb2/3)O3–Pb(ZrTi)O3 ferroelectric ceramics

Piezoceramic compositions Pb_1?zLa_z(NiSb)_0.05[(Zr_0.52Ti_0.48)_1?Z/4]_0.95O₃ with Z = 0.01–0.05 were synthesized by mixed oxide route to study the effect of Lanthanum (La) on crystal structure, microstructure, piezoelectric and ferroelectric properties. Calcination was performed at 1,060 °C and sintering at 1,270 °C for 1 h. X-Ray diffraction pattern indicated the polycrystalline microstructure along with co-existence of tetragonal and rhombohedral perovskite phases. Dielectric constant ( $ K_{3}^{T} $ ) was increased whereas piezoelectric voltage constant (g ₃₃) was decreased with increase in lanthanum. Dense microstructure was observed for the composition containing 3 mol% of lanthanum. This was resulted in optimum piezoelectric charge constant (d ₃₃ = 468 × 10^?12 C/N), electromechanical coupling factor (k _p  = 0.68), remanent polarization (P _r = 24.65 μC/cm²) and displacement (D = 2,012 nm). Results indicated that the composition Pb_0.97La_0.03(NiSb)_0.05[(Zr_0.52Ti_0.48)_0.9925]_0.95O₃ could be suitable for actuator applications. The composition Pb_0.98La_0.02(NiSb)_0.05[(Zr_0.52Ti_0.48)_0.995]_0.95O₃ resulted into moderately high value of voltage constant (g ₃₃ = 39.3 × 10^?12 V m/N) and optimum value of Figure of Merit (d ₃₃ × g ₃₃ = 16.2 × 10^?12 C V m/N²) indicated the usefulness for sensor and power harvesting applications.     

Effect of sintering process on electrical properties and ageing behavior of ZnO–V2O5–MnO2–Nb2O5 varistor ceramics

The effect of sintering process on microstructure, electrical properties, and ageing behavior of ZnO–V₂O₅–MnO₂–Nb₂O₅ (ZVMN) varistor ceramics was investigated at 875–950 °C. The sintered density decreased from 5.52 to 5.44 g/cm³ and the average grain size increased from 4.4 to 9.6 μm with the increase of sintering temperature. The breakdown field (E_{1 mA}) decreased from 6991 to 943 V/cm with the increase of sintering temperature. The ZVMN varistor ceramics sintered at 900 °C led to surprisingly high nonlinear coefficient (α = 50). The donor concentration (N_d) increased from 3.33 × 10¹⁷ cm⁻³ to 7.64 × 10¹⁷ cm⁻³ with the increase of sintering temperature and the barrier height (Φ_b) exhibited the maximum value (1.07 eV) at 900 °C. Concerning stability, the varistors sintered at 925 °C exhibited the most stable accelerated ageing characteristics, with %ΔE_{1 mA} = 1.5% and %Δα = 13.3% for DC accelerated ageing stress of 0.85 E_{1 mA}/85 °C/24 h.     

Physical and electrical properties of MnO2-doped Pb(Zr x Ti1−x )O3 ceramics

The effects of composition on the physical property change in the phase coexistence region between the tetragonal and rhombohedral phases have been investigated as a function of zirconium concentration, x, for the MnO₂-doped Pb(Zr _x Ti_1–x )O₃ (0.40x0.60) ceramics. The relative amount of phase coexisting between the tetragonal and rhombohedral phases affects greatly both dielectric and piezoelectric properties as a function of zirconium concentration. However, there are no detectable changes between the apparent density and microstructure. Also, in the coexistence region, the relative amount of coexistence of the rhombohedral phase increases with MnO₂ addition. The inflection points of the dielectric constant shift to lower zirconium concentration in proportion to the MnO₂ addition, owing to the substitution effect on the PZT lattice site.     

Electromechanical properties and anisotropy of single- and multi-domain 0.72Pb(Mg(1∕3)Nb(2∕3))O(3)-0.28PbTiO(3) single crystals

Complete sets of elastic, piezoelectric, and dielectric constants of 0.72Pb(Mg(1∕3)Nb(2∕3))O(3)-0.28PbTiO(3) single crystal poled along [111](c) (single domain) as well as non-polar axes [001](c) and [011](c) (multidomain) have been measured under natural conditions. These data allowed us to evaluate accurately the extrinsic contributions to the superior piezoelectric properties. Very large extrinsic contributions to the unusual anisotropies in multidomain crystals are confirmed. We found that the instability of domain structures is the origin of the low mechanical quality factor Q for the multidomain relaxor-based ferroelectric single crystals. Our results can provide useful guidance in future design of domain engineered materials.     

67 Pb(Mg1/3Nb2/3)O3-33PbTiO3单晶90铁电畴光学研究

采用偏光显微镜观察了67Pb(Mg1/3Nb2/3)O3-33PbTiO3固溶体铁电单晶在室温时90铁电畴结构.铁电畴结构与晶体质量有关,在正交偏光显微镜下光学透明晶体中存在着尺寸为23mm的均匀大畴,不同极化方向的大畴重叠形成雾状区,使晶体表现出光学质量宏观不均匀.在光学质量差的雾状晶体中则存在着0.1mm宽的110型带状孪生畴,使晶体形成表面浮凸,带状畴内还存在着90°亚畴.并对这些畴的形成作了讨论