PZ Ceramics Research Articles

Dielectric and ferroelectric properties of PMN–PT–PZ ceramics prepared via combustion technique

The fabrication of 0·53Pb (Mg1/3Nb2/3)O3–0·37PbTiO3–0·10PbZrO3 (PMN–PT–PZ) ferroelectric ceramics using the combustion technique and the effects of firing conditions on the phase structure, microstructure and electrical properties of the powders and ceramics were studied. Glycine was used as a fuel to reduce the reaction temperature. It was found that a single perovskite phase of PMN–PT–PZ powders was obtained from the sample calcined at 900°C for 2 h. The conventional technique uses two steps in the calcination process. The use of glycine in the combustion technique reduced the process to one step. The morphology of the PMN–PT–PZ powders showed an almost spherical shape and the average particle size increased from 0·12 to 2·51 μm when the calcination temperature was increased from 700 to 1000°C. The pure PMN–PT–PZ ceramics exhibited coexistant phases of the rhombohedral and the tetragonal perovskite phase in the samples sintered at a temperature lower than 1100°C. A second phase of pyrochlore was found in the samples sintered at temperatures higher than 1150°C. The PMN-PT-PZ ceramics sintered at 1100°C for 2 h exhibited the highest density, highest linear shrinkage and highest dielectric constant at Tc of 7·72 g cm−3, 16·13% and 18337 respectively. The densest PMN-PT-PZ ceramic exhibited good ferroelectric properties of (using an electric field at 30 kV cm−1) Pr = 26·9 μC cm−2 and Ec = 4·5 kV cm−1.

Effect of CuO Addition on the Microstructure and Electric Properties of Low‐Temperature Sintered 0.25PMN–0.40PT–0.35PZ Ceramics

Low‐temperature sintering of 0.25PMN–0.40PT–0.35PZ ceramics was investigated using CuO as a sintering aid. Effect of CuO on the sinterability, microstructure, and electric properties of 0.25PMN–0.40PT–0.35PZ system was systematically studied. The CuO addition significantly reduced the sintering temperature of 0.25PMN–0.40PT–0.35PZ from 1260°C to 950°C. SEM results indicated that a dense microstructure without any second phase was obtained when the amount of CuO was 0.25 wt%, which gave rise to high values of d33 = 532 pC/N and kp = 58.4%. A large field‐induced longitudinal strain ~2.28% (at 30 kV/cm) can also be obtained for 0.25 wt% CuO‐added specimens, which shows a great promise for multilayer actuator applications.

MPB design and crystal growth of PMN–PT–PZ relaxor ferroelectrics

Rhombohedral–tetragonal ferroelectric structural phase transition temperature (TR−T), far below the Curie temperature (Tc) in lead magnesium niobate–lead titanate (PMN–PT) relaxor ferroelectric single crystal, heavily restricts its further applications either as a sensor or transducer. To overcome this shortcoming, lead zirconate (PZ) was introduced into the PMN–PT pseudo-binary system to increase TR−T via the morphotropic phase boundary (MPB) composition design and optimization. According to the PMN–PT–PZ pseudo-ternary phase diagram, various compositions have been selected to discuss the relations between their phase structural transition and piezoelectric properties in the PMN–PT–PZ pseudo-ternary system. X-ray diffraction (XRD) investigation indicates clearly that PMN–PT–PZ ceramics with MPB compositions experience a typical structural phase transition process from rhombohedral phase to tetragonal phase. Remnant polarization (Pr=33.4μC/cm2) and piezoelectric coefficient (d33=1050pC/N) were obtained at the (001) cut PMN–PT–PZ single crystal. TR−T was increased up to 120°C by measuring its dependence of dielectric constant on temperature.

Fabrication of (Pb1-xBax)ZrO3 Ceramics via the Combustion Technique

(Pb1-xBax)ZrO3 with x = 0, 0.1 and 0.2 (PZ, PBZ10 and PBZ20) ceramics were synthesized via the combustion technique. (CO(NH2)2) was used as fuel to reduce the reaction temperature. The sintering temperatures were in the range of 1150°C–1350°C for 3 h. All calcined powders indexed in an orthorhombic structure and the purity of the perovskite phase was found in all the sintered pellet samples. The sintered pellets indexed in the orthorhombic structure for PZ and PBZ10 ceramics and in the rhombohedral structure for PBZ20 ceramics. The average grain size increased with an increase of sintering temperatures. The maximum density was observed in the sample sintered at 1250°C. The DSC measurement showed FE-PE phase transition temperature to be around 232°C, 194°C and 154°C, and the PE-FE phase transition temperature was around 229°C, 192°C and 152°C for x = 0, 0.1 and 0.2, respectively. The AFE to FE phase transition temperature was 229°C for PZ ceramics. The dielectric properties were also investigated.

Structural phase transition behaviour and electrical properties of Pb(Mg1/3Nb2/3)O3–PbTiO3–PbZrO3 ceramics

Piezoelectric ceramics with compositions of (1 − x − y)Pb(Mg1/3Nb2/3)O3–yPbTiO3–xPbZrO3 (PMN–PT–PZ), x = 0.025, 0.05, 0.075 and 0.1, close to the morphotropic phase boundary (MPB) were systematically investigated as a function of PT content (y). With increasing PT content, the structures of ceramics in every fixed PZ content series experience a gradual transition process from the rhombohedral to the tetragonal phase near the MPB. Electrical properties such as piezoelectric coefficient (d33), electromechanical factor (kp), remnant polarization (Pr) and dielectric constant (εr) in the respective series all exhibit the peak values corresponding to the structural phase transition near the MPB. Investigations on the temperature dependence of the dielectric constant of (0.95−y)PMN–yPT–0.05PZ ceramics show that an increased Curie temperature Tc and rhombohedral/tetragonal phase transition temperature TR–T, as well as relatively high electrical properties, can be obtained in some selected compositions. This indicates that the ternary system deserves further exploration for high-temperature applications, especially for the hot research on promising candidates for high-temperature relaxor-based ferroelectric single crystals.

High-strain piezoelectric ceramics and applications to actuators

PZT-based solid solutions are very attractive piezoelectric ceramics, because they exhibit excellent piezoelectric properties such as large piezoelectric constant. In this paper we describe the relationship between piezoelectric properties and compositions, and sintering behavior of PbNiNbTiO 3–PbTiO 3–PbZrO 3 (PNN–PT–PZ) ceramics and applications to the microactuators for magnetic disk drives. The MPB composition was determined by the temperature dependence of the relative permittivity and XRD patterns. The large piezoelectric constant ( d 33 = 1100 pm/V) was obtained at the MPB composition. Unique rotating symmetrical microactuators using PNN–PT–PZ ceramics show both wide stroke and high-resonant frequency. In this paper we also describe the applications of piezoelectric ceramics to tunable superconductive filters for future wireless communication systems. Low-temperature piezoelectric properties of PZT-based ceramics and frequency tunable mechanisms will be discussed. This work was supported in part by the Ministry of Internal Affairs and Communications (MIC) of Japan.

Low Temperature Sintering of ZnO-Doped 0.01Pb(Mg1/2W1/2)O3–0.41Pb(Ni1/3Nb2/3)O3–0.35PbTiO3–0.23PbZrO3 Ceramics

ZnO was added to 0.01Pb(Mg1/2W1/2)O3–0.41Pb(Ni1/3Nb2/3)O3–0.35PbTiO3–0.23PbZrO3 (0.01PMW–0.41PNN–0.35PT–0.23PZ) ceramics to reduce their sintering temperatures to below 900 °C. The effects of the ZnO additive on the densification and piezoelectric properties of the PMW–PNN–PT–PZ + 0.1 wt % Y2O3 + x wt % ZnO (0≤x≤2.5) ceramics were investigated. The structure of the PMW–PNN–PT–PZ ceramics was found to change from pseudocubic to tetragonal as their ZnO content was increased. The piezoelectric constant, the mechanical quality factor, and the electromechanical factor of the ceramics increased as their ZnO content increased. The optimum piezoelectric properties were found to be d33=594 pC/N, kp=57%, and Qm=64, for PMW–PNN–PT–PZ + 0.1 wt % Y2O3 + 1.5 wt % ZnO sintered at 900 °C for 2 h.

A comparative dielectric relaxation study of PMN–PT and PMN–PZ ceramics using impedance spectroscopy

AC-impedance spectroscopic studies in the temperature range of 30–400 °C are carried out on solid solutions of lead magnesium niobate (PMN) with lead titanate (PT) and lead zirconate (PZ), both of them in the 65/35 atomic ratio. For PMN–PT this corresponds to the morphotropic phase boundary composition (with normal ferroelectric behaviour), and for PMN–PZ it is near the phase boundary between normal ferroelectric and relaxor ferroelectric compositions. The variation of dielectric permittivity with temperature at different frequencies shows normal ferroelectric and relaxor-like dependence for PMN–PT and PMN–PZ, respectively. Temperature-dependent spectroscopic modulus plots reveal a much broader peak for PMN–PZ compared to that for PMN–PT, which is consistent with the dielectric behaviour. PMN–PT shows nearly ideal Debye behaviour below T m (the temperature of the permittivity maximum) and the behaviour departs from ideality above T m, whereas non-ideal Debye behaviour is seen both below and above T m for PMN–PZ. Complex modulus plots fit well with two depressed semicircles and three depressed semicircles, respectively, for PMN–PT and PMN–PZ. The relaxation observed in the spectroscopic plots around 1 MHz for PMN–PT has been assigned to polarisation relaxation expected for normal-sized domains. No such relaxation could be observed for PMN–PZ around 1 MHz because of the mesoscopic domain sizes.

Effects of CuO and ZnO Additives on Sintering Temperature and Piezoelectric Properties of 0.41Pb(Ni1/3Nb2/3)O3–0.36PbTiO3–0.23PbZrO3 Ceramics

ZnO-added 0.41PNN–0.36PT–0.23PZ ceramics cannot be sintered below 950°C. However, when CuO is added, the liquid phase forms and specimens can be sintered even at 850°C. The dielectric constant (εT3/εo), piezoelectric constant (d33) and electromechanical coupling factor (kp) increase with the addition of CuO and this is due to the enhancement of the density of the specimens. When CuO is added to 0.41PNN–0.36PT–0.23PZ ceramics, improvements of density, εT3/εo, d33 and kp are also observed. However, the d33 and kp values of the CuO-added 0.41PNN–0.36PT–0.23PZ ceramics are less than those of the CuO- and ZnO-added specimens. Therefore, ZnO is effective in improving the piezoelectric properties of 0.41PNN–0.36PT–0.23PZ ceramics. Good dielectric and piezoelectric properties of d33=575(pC/N), kp=0.55 and εT3/εo= 3900 are obtained for 0.41PNN–0.36PT–0.23PZ+3.0 mol% ZnO with 1 mol% CuO sintered at 900°C for 2 h.

Preparation and characterization of lead zirconate ceramics from high-energy ball milled powder

Lead zirconate (PbZrO 3 or PZ) powder was successfully synthesized by a high-energy ball milling process using oxides as starting materials. The milled powders were characterized by XRD, SEM and particle size analysis. Perovskite PZ phase is predominant in the milled powder with an average particle size of about 20 nm. The sintering behavior of the milled powder was investigated by a dilatometer, showing a maximum densification occurred at about 950°C. PZ ceramics were obtained by sintering the milled powder at different temperatures. The microstructure, grain growth, density and dielectric property of the PZ ceramics as a function of sintering temperature were investigated and discussed.

Effects of MnO2 Addition on Piezoelectric and Ferroelectric Properties of PbNi1/3Nb2/303-PbTiO3-PbZrO3 Ceramics.

High-density 0.5PbNi1/3Nb2/3O3⋅0.345PbTiO3⋅0.155PbZrO3 (0.5PNN⋅0.345PT⋅0.155PZ) ceramics were prepared by normal sintering with the addition of 0-3.66mol% MnO2 and their piezoelectric and ferroelectric properties were investigated. The effect of MnO2 addition on significantly lowering the value of tan δ in the range of 0.37 to 0.93mol% was proven. The lowest value (=0.37%) of tan δ was obtained in ceramics with 0.75mol% MnO2. Electromechanical coupling factors, kp and k31, and the piezoelectric constant, d31, decreased with increasing amount of MnO2 addition. The highest values of kp, k31 and d31 were 0.66, 0.38 and -362pC/N, respectively, and were obtained in the ceramics without MnO2. The effect of MnO2 addition on improving the value of the mechanical quality factor, Qm, was proven in the range of 0.93 to 1.85mol% and the improvement was around twenty times that of the sample without MnO2. The distortion in the shape of P-E hysteresis loops for samples with MnO2 addition suggested that oxygen vacancies formed by substituting Mn3+ ions for B-site ions (e.g., Ti4+ and Zr4+ ions) in the perovskite structure partially inhibited the polarization reversal in the ferroelectrics. 0.5PNN⋅0.345PT⋅0.155PZ ceramics with 0.75-0.93mol% MnO2 show great promise as practical materials for piezoelectric applications.

Densification behaviors and piezoelectric properties of MnO2, SiO2-doped Pb(Ni1/3Nb2/3)O3–PbTiO3–PbZrO3 ceramics

The roles of additives (MnO2, SiO2, and CdO) in controlling microstructural development and piezoelectric properties of Pb(Ni1/3Nb2/3)O3– PbTiO3–PbZrO3(PNN–PT–PZ) ceramics were systematically examined. The addition of SiO2 (<1 wt. %) to the pseudoternary PNN–PT-PZ system enhances densification, but suppresses grain growth significantly. On the other hand, the presence of MnO2 expedites the rate of grain growth without increasing the rate of densification appreciably. The observed difference in the grain-growth behavior was discussed in terms of the viscosity of liquid phase formed during sintering and the diffusion-controlled process for the solute-atoms transport. The rapid increase in the mechanical quality factor (Qm) and the decrease in the relative dielectric permittivity (∊r) and d33 for the MnO2-doped specimens indicate the formation of oxygen vacancies by the dissolution of Mn-atoms into the B-sites of perovskite structure. On the contrary, the presence of CdO (2 mol %) remarkably increases ∊r and d33 of PNN–PT–PZ ceramics.