Fabrication of Optically Transparent Lead Lanthanum Zirconate Titanate ((Pb,La)(Zr,Ti)O3) Ceramics by a Three-Stage-Atmosphere-Sintering Technique

An easy technique has been developed to fabricate optically transparent lanthanum-modified lead zirconate titanate (PLZT) ceramics. This technique consists of three stages: (1) sintering in an oxygen atmosphere, (2) elimination of pores in a carbon dioxide atmosphere, and (3) elimination of oxygen vacancies in an oxygen atmosphere. The carbon dioxide atmosphere enhances the diffusion of oxygen from the pores to outside the sintered body. The experimental results reveal that use of a carbon dioxide atmosphere effectively decreases residual pores and improves optical transmittance. From commercially available raw powders, an optical transmittance of 51% (wavelength of 550 nm) can be achieved for 0.7 mm thick polished PLZT9/65/35 ceramics using a carbon dioxide atmosphere, whereas the value is only 34% without a carbon dioxide atmosphere. The advantage of this technique is that PLZT ceramics having high optical quality can be obtained using conventional sintering tools.     

Effect of Manganese Ion Diffusion on the Microstructural Evolution of Lead Lanthanum Zirconate Titanate Ceramic

Microstructural evolution of lead lanthanum zirconate titanate (PLZT) ceramics caused by diffusion of the Mn ion was observed. Specimens with layered structures were fabricated by copressing a PLZT powder (9/65/35) doped with Mn and same PLZT powder without the dopant. When the copressed specimen was sintered at 1200°C in air, the Mn ion diffused out of the doped region. The region originally containing the Mn ions was totally free of pores while all other regions remained porous. The formation of lattice vacancies, as a result of Mn diffusion, was attributed to the enhanced material transport and the resultant rapid densification.     

Direct-Write Fabrication of Pb(Nb,Zr,Ti)O3 Devices: Influence of Paste Rheology on Print Morphology and Component Properties

Lead niobium zirconate titanate (PNZT) pastes with tailored rheological properties have been developed for direct-write fabrication of thick-film capacitor elements in highly integrated, multifunctional electroceramic devices. Such pastes exhibited pseudoplastic behavior with a low shear apparent viscosity of roughly 1 × 10⁶ cP. On aging, the degree of shear thinning and the low shear apparent viscosity decreased. Pastes prepared from as-received powders attained printable, steady-state viscosities of ∼2 × 10⁵ cP after 50 days of aging. In contrast, pastes prepared from dispersant-coated powders showed no measurable rheological changes after 1 day of aging. Square elements were patterned on dense alumina substrates or Teflon sheets. Leveling behavior as a function of time for single line prints, and the resulting surface topographies of dried PNZT films were measured by laser profilometry. PNZT layers sintered at varying temperatures between 950° and 1050°C for 5 h in either air or a lead-rich atmosphere yielded porous microstructures as revealed by scanning electron microscopy (SEM). Such layers exhibited dielectric constants ( K ) of 1400–1570 at 1 kHz with dissipation factors ( D ) of less than 4.1%.     

Robocast Pb(Zr0.95Ti0.05)O3 Ceramic Monoliths and Composites

Robocasting, which is a computer-controlled slurry-deposition technique, was used to fabricate ceramic monoliths and composites of chemically prepared Pb(Zr_0.95Ti_0.05)O₃ ceramics. The densities and electrical properties of the robocast samples were equivalent to those obtained for cold isostatically pressed parts formed under a pressure of 200 MPa. Three-layer robocast composites that consisted of alternating layers of different sintered densities—93.9%/96.1%/93.9%—were fabricated using different levels of organic pore-former additions. Modification from a single-material to a multiple-material deposition robocaster was essential for the fabrication of composites that could withstand repeated cycles of saturated polarization switching under fields of 30 kV/cm. Furthermore, these composites withstood a poled ferroelectric-to-antiferroelectric phase transformation that was induced by a hydrostatic pressure of 500 MPa, during which strain differences on the order of 0.8% occurred between the composite elements.     

Pressure-Induced Phase Transformation of Controlled-Porosity Pb(Zr0.95Ti0.05)O3 Ceramics

Chemically prepared Pb(Zr_0.95Ti_0.05)O₃ (PZT 95/5) ceramics were fabricated with a range of different porosity levels, while grain size was held constant, by systematic additions of added organic pore former (Avicel). Use of Avicel in amounts ranging from 0 to 4.0 wt% resulted in fired ceramic densities that ranged from 97.3% to 82.3%. Hydrostatic-pressure-induced ferroelectric (FE) to antiferroelectric (AFE) phase transformations were substantially more diffuse and occurred at lower hydrostatic pressures with increasing porosity. An ∼12 MPa decrease in hydrostatic transformation pressure per volume percent added porosity was observed. The decrease in transformation pressure with decreasing density was quantitatively consistent with the calculated macroscopic stress required to achieve a specific volumetric macrostrain (0.40%). This strain was equivalent to experimentally measured macrostrain for FE-to-AFE transformation. The macroscopic stress levels were calculated using measured bulk modulus values that decreased from 84 to 46 GPa as density decreased from 97.3% to 82.3%. Good agreement between calculated and measured values of FE-to-AFE transformation stress was obtained for ceramics fired at 1275° and 1345°C.     

Electromechanical Properties of Pb(Yb1/2Nb1/2)O3-PbZrO3-PbTiO3 Ceramics

The electromechanical and electric-field-induced strain properties of x Pb(Yb_1/2Nb_1/2)O₃· y PbZrO₃·(1− x − y )PbTiO₃ ( x = 0.12, 0.25, 0.37; y = 0.10–0.40) ceramics have been studied systematically as a function of Pb(Yb_1/2Nb_1/2)O₃ (PYN) content and PbZrO₃/PbTiO₃ (PZ/PT) ratio. In addition, the effect of MnO₂ on the electromechanical properties of 0.12Pb(Yb_1/2Nb_1/2)O₃·0.40PbZrO₃·0.48PbTiO₃ was also investigated. The maximum transverse strain values of 1.6 × 10⁻³ for x = 0.12, 1.45 × 10⁻³ for x = 0.25, and 1.36 × 10⁻³ for x = 0.37 were obtained at the compositions which were regarded as the morphotropic phase boundary (MPB). The transverse strain was maximized at the MPB composition. The value of the maximum electromechanical coupling coefficient was 0.69 for y = 0.40 and x = 0.12 composition. In the 0.12Pb(Yb_1/2Nb_1/2)O₃·0.40PbZrO₃·0.48PbTiO₃ composition, the temperature of the maximum dielectric constant decreased and the grain size increased with an addition of MnO₂. The electromechanical coupling coefficient decreased while the mechanical quality factor rapidly increased with an addition of MnO₂. These resulted mainly from the acceptor effect of manganese ions that were produced by doping MnO₂ into the perovskite structure.     

Lanthanum-Modified (1 – x)(Bi0.8La0.2)(Ga0.05Fe0.95)O3·xPbTiO3 Crystalline Solutions: Novel Morphotropic Phase-Boundary Lead-Reduced Piezoelectrics

(1 – x )(Bi_0.8La_0.2)(Ga_0.05Fe_0.95)O₃· x PbTiO₃ (BLGF-PT) crystalline solutions have been fabricated by solid-state reactions. BLGF-PT has single perovskite phase structure with a rhombohedral–tetragonal (FE_r-FE_t) morphotropic phase boundary (MPB) at a PT content of x = 0.43. Lanthanum substitution has been found to increase the insulation resistance and decrease the coercive field down to 20 kV/cm, which results in significant improvements in dielectric and piezoelectric properties of BLGF-PT. The dielectric constant, loss tangent, Curie temperature, remnant polarization, piezoelectric d ₃₃ constant, and planar coupling factor of 1760, 0.05, 264°C, 33 μC/cm², 295 pC/N, and 0.36, respectively, have been achieved for BLFG-PT in the vicinity of the MPB. Compared with conventional Pb(Zr,Ti)O₃ (PZT) piezoelectric ceramics, the BLGF-PT is a competitive alternative piezoelectric material with decreased lead content.     

热压烧结对锆钛酸铅镧陶瓷电卡效应的影响

探讨热压烧结工艺对PLZT(锆钛酸铅镧)陶瓷材料介电击穿性能、饱和极化强度以及电卡性能的影响。通过X射线衍射和扫描电子显微镜,分析陶瓷样品的相组成和微观结构。结果表明,热压烧结法有助于控制陶瓷晶粒的生长,提高陶瓷的致密度并增大陶瓷的介电击穿场强,从而有效提高陶瓷的电卡性能以及电卡转换效率。在328 K(55℃)与478 K(205℃)附近,分别发生低温铁电三方相到高温铁电三方相的相变(FRL-FRH)以及高温铁电三方相到立方顺电相(FRH-Pc)的相变,展现了比较好的弛豫性,在室温下达到3.6 K的绝热温变与1.8×0-7(K·m)/V的电卡转换效率,具有良好的电卡性能。     

C60 Nanowhiskers in a Mixture of Lead Zirconate Titanate Sol–C60 Toluene Solution

Fine fibrous structures of C₆₀ with a diameter on the order of nanometers were discovered in a lead zirconate titanate sol ultrasonically mixed with a toluene solution of C₆₀. By transmission electron microscopy observations, they were identified as single-crystalline fibers of C₆₀ with submicrometer diameters, i.e., nanowhiskers of C₆₀. The C₆₀ nanowhiskers showed thin slablike TEM images, and the growth axis of the nanowhiskers was parallel to the 〈110〉 close-packed direction of a fcc crystal system of C₆₀.     

Electrostrictive and Dielectric Response in Lead Magnesium Niobate–Lead Titanate (0.9PMN · 0.1PT) and Lead Lanthanum Zirconate Titanate (PLZT 9.5/65/35) under Variation of Temperature and Electric Field

In situ measurements of electrostrictive strain and effective dielectric constant for two ferroelectric relaxor materials, lead magnesium niobate–lead titanate (0.9PMN · 0.1PT) and lead lanthanum zirconate titanate (PLZT 9.5/65/35), were performed in the temperature ranges near their respective mean Curie points under the variation of applied electric field. The measurement results show that the polarization-related electrostrictive coefficients Q_ij are not constant under variation of temperature and electric field. The observed anomaly in Q_ij indicates the dynamic behavior of the existing micropolar domains and its coupling to local defect structure. The data also support the idea that at temperatures far above the mean Curie point, there is still a substantial amount of micropolar domain and the response of the relaxor materials at the experimental temperature range is from the combined contributions due to induced polarization and micropolar domain flipping.     

Crystallization of Fine, Chemically Prepared Lead Lanthanum Zirconate Titanate Powders at Low Temperature

Fine, homogeneous lead lanthanum zirconate titanate (PLZT) powder prepared by the hydrolysis of an aqueous nitrate solution with ammonia gas exhibits high reactivity when calcined. The minimum temperature for crystal formation in PLZT is 400°C. The kinetics of crystallization between 400° and 600°C are studied isothermally by XRD. The isothermal crystallization process is best fitted to a first-order equation derived for a random, nucleation-controlled system on a large number of small particles with an activation energy of 297 kJ/mol. Characterization of the powder by XRD line-broadening and BET surface-area examination in the range 400° to 500°C shows a microstructure consisting of ∼20-nm subunits agglomerated into ∼60-nm particles. Each subunit evidently generates a single nucleus, which grows within that subunit.     

Preparation of Dense Lead Magnesium Niobate–Lead Titanate (Pb(Mg1/3Nb2/3)O3–PbTiO3) Ceramics by Spark Plasma Sintering

The effect of spark plasma sintering (SPS) on the densification behavior of Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ ceramics has been investigated. Specimens with a density of >99% of the theoretical density (TD) were obtained using SPS treatment at 900°C. Through normal sintering at 1200°C, however, the density of the specimen was only ∼92% of TD.     

Microstructures and Pyroelectric Properties of Multicomposition 0.9PbZrO3·xPbTiO3·(0.1−x)Pb(Zn1/3Nb2/3)O3 Ceramics

The microstructures and pyroelectric properties of multicomposition 0.9PbZrO₃· x PbTiO₃·(0.1− x )Pb(Zn_1/3Nb_2/3)O₃ (PZ–PT–PZN) ceramics were investigated. The PZ–PT–PZN ceramics with nearly theoretical density were prepared by spark plasma sintering at low temperature (800°C) for a very short time (10 min) from two original compositions with x = 0.025 and x = 0.050. The heat treatment was successfully used to control the diffusion between the different compositions in such ceramics. For ceramics heat-treated at 900°C, two pyroelectric peaks corresponding to the original compositions were observed. When the heat-treatment temperature was increased to 1200°C, these two pyroelectric peaks combined into one sharp pyroelectric peak, which corresponds to average composition. When the spark-plasma-sintered ceramics were heat-treated at 950°C, a high and stable pyroelectric coefficient (>100 nC·cm⁻²·K⁻¹) over a wide temperature range (23°–47°C) was obtained. It was found that the pyroelectric properties strongly depended on the microstructures.     

Preparation of Lead Lanthanum Zirconate Titanate (PLZT, (Pb,La)(Zr,Ti)O3) Fibers by Sol-Gel Method

Lead lanthanum zirconate titanate (PLZT, (Pb,La)(Zr,-Ti)O₃) ceramic fibers were prepared by the sol-gel method from a solution of lead acetate trihydrate, lanthanum isopropoxide, zirconium n -propoxide, and titanium isopropoxide that contained 2-methoxyethanol as the solvent. The sols obtained from the solution were concentrated at 156°-174°C for 2 h. Concentration at higher temperatures resulted in more-viscous sols of higher specific gravities. The concentration resulted in the formation of spinnable sols, which had viscosities >10⁵ mPas and exhibited Newtonian flow properties. These spinnable sols were formed to be so stable that no change in viscosity and spinnability was observed for more than three months when stored in a sealed container at room temperature. Gel-to-ceramic fiber conversion was investigated by means of X-ray diffractometry, infrared spectroscopy, and thermal analysis. Single-phase perovskite PLZT ceramic fibers 5-200 μm in diameter and >20 cm in length were obtained. Scanning electron microscopy (SEM) observation and Brunauer-Emmett-Teller (BET) measurement showed that heat treatment of the fibers at a lower rate resulted in the formation of fibers of denser microstructure. Although the SEM image of the cross section of the fibers revealed a relatively dense microstructure and a laser beam could be transmitted through a fiber 6 mm in length, BET measurement of the fibers indicated that the fibers had more than a few percent of open porosities, and scattering of light was observed in the laser-beam guiding test.     

Effect of Lead Zirconate Titanate Seeds on PtxPb Formation during the Pyrolysis of Lead Zirconate Titanate Thin Films

Lead zirconate titanate (PZT) thin films were prepared on platinized silicon substrates by dip-coating using a modified diol-based sol–gel route without and with up to 5 mol% PZT nanometric seeds dispersed in the precursor sol. A metastable intermetallic Pt _x Pb phase formed at the early stages of heat treatment. XRD, TEM, and RBS revealed that the thickness and stoichiometry of the Pt _x Pb layer varied with the concentration of seeds and heat treatment of the films. The relation of the Pt _x Pb layer to the final crystalline texture of the PZT thin films is reported and discussed.     

Synthesis of Lead Nickel Niobate–Lead Zirconate Titanate Solid Solutions by a B-site Precursor Method

A modified processing method for lead nickel niobate–lead zirconate titanate (Pb(Ni_1/3Nb_2/3)O₃–Pb(Zr,Ti)O₃, PNN–PZT) solid solutions is presented. This method is based on the high-temperature synthesis of a precursor that contains all the B-site cations (Ti, Zr, Ni, and Nb). This synthesis yields a diphasic mixture that contains a ZrTiO₄-like phase and a rutile-like phase. Both phases exhibit a cationic valence of 4; thus, it is concluded that the mixing of Ni and Nb cations is adequate for the preparation of PNN–PZT solid solutions. Indeed, a pure perovskite phase has been obtained after calcination with lead oxide for compositions that contain 40 and 50 mol% PNN. Moreover, their electromechanical properties have been shown to be superior to values reported for standard columbite routes. This conclusion has been interpreted in terms of enhanced chemical homogeneity.     

Growth of High-Quality Pb((Zn1/3Nb2/3)0.91Ti0.09)O3 Single Crystals by Excess ZnO Addition

A high-quality single crystal of Pb((Zn_1/3Nb_2/3)_0.91Ti_0.09)O₃ (PZNT 91/9), 40 mm in diameter and 20 mm in length, was successfully grown using the solution Bridgman method with a slight excess amount of ZnO. High-quality wafers were sliced from the light-brown single crystal. No PbO inclusions or opaque areas were observed in the transparent wafers. An array probe for echocardiography was constructed with the single-crystal wafer, and its superior performance was demonstrated.     

Fracture Mechanisms in Ferroelectric-Ferroelastic Lead Zirconate Titanate (Zr: Ti=0.54:0.46) Ceramics

Fracture toughness, K _IC, of a single-phase commercial lead zirconate titanate (PZT) ceramic (Zr/Ti=0.54/0.46) of tetragonal structure ( c/a =1.019) was measured using the single edge notched beam method above and below the Curie temperature. Domain switching (poling) under electrical and mechanical loading was examined using X-ray diffraction. Surface grinding, electrical poling, and mechanical poling caused crystallographic texture. Similar texture, indicative of domain switching, was also observed on fracture surfaces of some saples fractured at room temperature. At room temperature, the highest K _IC measured was 1.85 MPa·m^1/2, while above the Curie temperature it was about 1.0 MPa·m^1/2. Cracks emanating from Vickers indents in poled samples were different in the poling and the transverse directions. The difference in crack sizes is explained on the basis of domain switching during crack growth. These results indicate that ferroelastic domain switching (twinning) is a viable toughening mechanism in the PZT materials tested.     

Perovskite Formation and Dielectric Characteristics of Pb(Zn1/3Ta2/3)O3 with PbTiO3 Substitution

Perovskite developments in the Pb(Zn_1/3Ta_2/3)O₃–PbTiO₃ system were explored. Formation yields and lattice parameters of the perovskite were determined from X-ray diffractometry results. Weak-field low-frequency dielectric properties of the system ceramics were investigated, followed by microstructure examination. Perovskite started to develop in Pb(Zn_1/3Ta_2/3)O₃ after the introduction of 30 mol% PbTiO₃, whereas complete stabilization was accomplished at 60% substitution. Dielectric relaxation behavior was not substantial across the entire composition range, whereas phase transition modes changed from diffuse to sharp with increased PbTiO₃ fraction.     

助熔剂法生长的锆钛锡酸铅镧(PLZST)晶体及生长余料的组分分析

以PbO-PbF2复合体作为助熔剂,采有助熔剂自发成核缓冷法率先制备出成分为（Pb0.94La0.04)(Zr0.37Ti0.18Sn0.45)O3的驰豫型复合钙钛矿结构锆钛锡酸铅镧（PLZST）晶体,合适的生长工艺为：助熔剂中PbO与PbF2的摩尔比为0.55:0.45,原料与助熔剂的摩尔比为1：1,保温温度1250℃,保温时间12h,快降温速率为50－100℃／h,慢降温速率为1－5℃/h,快速降温与慢速降温的转变温度为1150℃,本工作对晶体及晶体生长余料中的组分进行了分析,结果表明：对一定组成的初始配料,PLZST晶体组成相对富La,Ti和Zr,生长后的余料相对富Sn,PLZST晶体中存在两种包裹体缺陷,晶体除包裹体以外各元素分布均匀,生长余料中各元素分布较均匀,存在某些元素的相对富集区域。