Novel thermal expansion of lead titanate

Lattice parameters of lead titanate were precisely re-determined in thetemperature range of-150-950 deg C by high precision XRPD measurements. It was clarified that therewas no any evidence for a new phase transition at low tempera-lures. Tetragonal distortion straindecreases with temperature increasing. A novel thermal expansion was observed, positive thermalexpansion from -150 deg C to room temperature (RT) and above 490 deg C, and the negative thermalexpansion in the temperature range of RT-490 deg C. A big jump of thermal expansion coefficient isattributed to the tetragonal-cubic phase transition. A rationalization for the negative thermalexpansion of PbTiO_3 is due to the decrease of anion-anion repulsion as polyhedra become moreregular at heating. The mechanisms of positive and negative thermal expansions were elucidated asthe same nature in the homogenous tetragonal phase at present case.

THE PREPARATION AND PHOTOCATALYTIC ABILITY OF LEAD TITANATE

he perovskite-type PbTiO3 has been synthesized by the method of mixed oxides. The appropriate conditions for preparing have been reported. The obtained PbTiO3 powder is pure and fine. The decolorization of dyes in a PbTiO3 suspension system is over 90%. In this paper the photocatalytic ability of PbTiO3 and the factors of influence are discussed.

Rapid Synthesis and FT-Raman Spectroscopic Study of Lanthanum Modified Lead Titanate Nanocrystals

Pb_ 1-xLa_xTi_ 1-x/4O_3 nanocrystals with different amounts of lanthanum were prepared by modified sol-gel method and detected by FT-Raman spectra at 288 and 378 K, respectively. The improved synthetic technique used in this paper could obtain nanocrystals with apparently promoted synthetic speed from a few days to several hours (4 times faster of hydrolytic process than that of traditional sol-gel method and reduced preparation period of gel from 24 h to several hours) at relatively lower temperature by hydrolysis of sol to gel through adding methyl alcohol/water solution into sol under vigorous stirring and annealed the fresh gel directly. The effects of lanthanum′s amount, annealed temperature and nanocrystals′ grain size of Pb_ 0.9La_ 0.1Ti_ 0.975O_3 nanocrystals on frequency, shape and width of the phonon peak were also discussed in detail.

Hydrothermal Synthesis and Phase-, Morphology-Evolution Mechanism of Lead Titanate Nanostructures Assisted with Tetramethylammonium Hydroxide

Lead titanate nanostructures with different phases and morphologies, layered hexagonal PbTiO2（CO3）0.3- （NO3）0.35（OH） nanosheets, pyrochlore Pb2Ti2O6 nanodendites, pre-perovskite PbTiO3 nanofibres and perovskite PbTiO3 nanoplates, have been synthesized via a conventional hydrothermal route assisted with different concentra- tions of tetramethylammonium hydroxide （TMAH）. X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and high-resolution TEM （HRTEM） were employed to characterize the phase, morphology and growth behavior of the synthesized samples. The results reveal that at low TMAH concen- tration the obtained samples are mainly of PbTiO2（CO3）o.3（NO3）0.35（OH） nanosheets. With the TMAH concentration increasing, the obtained samples change to pyrochlore Pb2Ti2O6 nanodendites, pre-perovskite PbTiO3 nanofibres and perovskite PbTiO3 nanoplates in turn. With the basis of the experimental results, the phase- and morpholo- gy-evolution mechanism of the lead titanate nanostructures is discussed by combining the analysis of the lattice structure feature and the properties of TMAH.

Influence of KF substitution on the ferroelectric phase transition of lead titanate single crystals studied by Brillouin light scattering

The elastic properties of KF-substituted perovskite lead titanate(PbTiO_(3))were investigated by dielectric measurements and Brillouin light scattering.The ferroelectric phase transition occurred at substantially lower temperature due to KF substitution,which was attributed to the modification of the covalency in Pb–O and Ti–O bonds.The longitudinal acoustic(LA)mode of KF-substituted PbTiO_(3) showed a frequency softening in the paraelectric phase,which was accompanied by increasing acoustic damping.This indicated that polarization fluctuations responsible for the acoustic anomalies were enhanced by KF substitution.

Improving the fatigue endurance of lead zirconate titanate thin films through PbO interfacial modification

The effects of the modification of electrode/ceramic interfaces through a chemical solution deposition-derived PbO buffer layer on the fatigue endurance of lead zirconate titanate（PZT） thin films were investigated.The grain size and the surface roughness of the PZT films increased through PbO interfacial modification.Moreover,the PZT films with PbO interfacial modification had a better crystallographic structure and no evident secondary phases were observed.While the remanent polarization and dielectric constant were reduced,the fatigue endurance was improved.Based on the results,the mechanism for the fatigue endurance improvement was discussed.

Lead zirconate titanate behaviors in an LDMOS

The behaviors of lead zirconate titanate （PZT） deposited as the dielectric for high-voltage devices are investigated experimentally and theoretically. The devices demonstrate not only high breakdown voltages above 350 V, but also excellent memory behaviors. A drain current–gate voltage （ID-VG） memory window of about 2.2 V is obtained at the sweep voltages of ±10 V for the 350-V laterally diffused metal oxide semiconductor （LDMOS）. The retention time of about 270 s is recorded for the LDMOS through a controlled ID-VG measurement. The LDMOS with memory behaviors has potential to be applied in future power conversion circuits to boost the performance of the energy conversion system.

Local Structure Analysis of Lead Zinc Niobate-Barium Titanate Ceramic by X-Ray Absorption Spectroscopy and Density Functional Calculation

The local structure of an alternative Pb（Zn1/3Nb2/3）O3-based perovskite ceramic is investigated. The 0.07BaTiO33-0.93Pb（Zn1/3Nb2/3）O3 ceramic is synthesized using a combination of Zn3Nb2O8 B-site precursor and BaTiO33 perovskite phase stabilizer. Then, x-ray absorption spectroscopy and density functional theory are employed to calculate the local structure configuration and formation energy of the prepared samples. Ba2＋ is found to replace Pb2＋ in AA-site with Zn2＋ occupying BB-site in Pb（Zn1/3Nb2/3）O3, while in the neighboring structure, Ti4＋4＋ replaces Nb5＋5＋ in BB-site with Pb2＋2＋ occupying AA-site. With the substitution of BaTiO33 in Pb（Zn1/3Nb2/3）O3, the bond length between Zn2＋ and Pb2＋ is longer than that of the typical perovskite phase of Pb（Zn1/3Nb2/3）O3. This indicates the key role of BaTiO33 in decreasing the steric hindrance of Pb2＋ lone pair, and the mutual interactions between Pb2＋ lone pair and Zn2＋ and the formation energy is seen to decrease. This finding of the formation energy and local structure configuration relationship can further extend a fundamental understanding of the role of BaTiO33 in stabilizing the perovskite phase in PbZn13Nb23O3-based materials, which in turn will lead to an improved preparation technique for desired electrical properties.

Studies on the structure and microstructure of lead strontium titanate thin films

Pb1-xSrxTiO3 （0≤x≤0.9） thin films on Si （100） substrate were prepared by the sol-gel process and their characteristics were investigated as a function of strontium content（x）. With increasing of the strontium content, the tetragonality （c/a） was slightly decreased, the splitting peaks become less prominent and the splitting peaks tend to merge into a single peak. Furthermore, the grain size of the films was systematically reduced with the increase in strontium content.

FABRICATION OF PIEZOELECTRIC BIMORPH USING LEAD ZIRCONATE TITANATE THIN FILM DEPOSITED BY HYDROTHERMAL METHOD

In order to describe the characteristics of piezoelectric bimorph, properties of lead zirconate titanate （LZT） film are studied by X-ray diffraction （XRD） and scanning eletron microscope （SEM）. The ratio of PbTiOJPbZrO3 in LZT is 53/47, which is around morphotropic phase boundary （MPB）. LZT film is composed of cubic particles with the average size of 5 ~ma. Density of thin film is figured out through the datum measured in experiments. The displacement model used to analyze the driving ability of bimorph is set up, and the effect of elastic intermediate layer is taken into account. Piezoelectric coefficient of LZT film is worked out by using the displacement model. Experiments of driving ability show that deformation of bimorph free end does not increase with times of crystal growth processes and the maximum deformation is obtained after two times crystal growth processes. Finally, the ferroelectric property of the bimorph is investigated and coercive voltage of the bimorph is obtained.

Semi-empirical estimation for enhancing negative thermal expansion in PbTiO_(3)-based perovskites

Generally,most materials expand when heated and contract when cooled,whereas negative thermal expansion(NTE)materials are very rare.As a typical NTE material,PbTiO_(3) and related compounds have drawn particular interest in recent years.The discovery of an enhanced NTE system in PbTiO_(3) is beneficial to deepen our understanding of its mechanism and regulate its properties.At present,the method of discriminating an enhanced NTE material based on PbTiO_(3) is not universal.Here,we propose a semi-empirical method through evaluating the average lattice distortion in related systems to estimate the relative coefficient of thermal expansion conveniently.The rationality of the method was verified by the analysis of the 0.6PbTiO_(3)-0.4Bi(Ga_(x)Fe_(1-x))O_(3) system.So far,all PbTiO_(3)-based compounds with enhanced NTE conform well to this method.This method provides the possibility to find more enhanced NTE PbTiO_(3)-based materials.

Structure and Shape Control of Hydrothermally Synthesized PbTiO_3 --Effects of pH and Complexing Agents

Tabular PE PbTiO 3, spherical PY PbTiO 3, and acicular PX PbTiO 3 powders were hydrothermally synthesized from triethanolamine(TEA) complexed precursor; clubbed PE PbTiO 3 powders were obtained from diethanolamine(DEA) complexed precursor. The effects of pH of the hydrolyzation as well as complexing agents including TEA, DEA, and MEA(monoethanolamine) on the structure and the morphology of PbTiO 3 powders are discussed. The optimal conditions for hydrothermal syntheses of acicular and clubbed PbTiO 3 powders have been established. The products were characterized by means of XRD, TEM and other techniques.

Study on Polymer Films with Thermal Stability

New polymer film materials with good properties are reported. The difference between positive and negative coronas is also given. The films have good transmittance, excellent thermal and long-term stability, low dielectric constant, and high glass transition temperature.

Structural Morphological and Dielectric Properties of Pb1-xNixTiO3 Doped with Ni

In this paper, we have reported a conformable PbTiO3 ceramics doped with Ni by standard double sintering technique as well as chemical co-precipitation method which were successfully synthesized by means of carefully controlled processing parameters. Single phase formation was confirmed through X-Ray Diffraction (XRD) analysis, IR spectroscopy, SEM micrograph and TEM images. Discussion and comparison between both preparation methods were made on the basis of observed results. The tetragonality c/a decreased from 1.049 to 1.0276 for ceramic samples and decreased from 1.06519 to 1.0365 for co-precipitation samples by increasing Ni content. TEM images show small ferroelectric domains of about 3 to 14 nm for the co-precipitation sample and 26 to 48 nm for the ceramic samples. The SEM of co- precipitation samples shows that the microstructure is very dense. The behavior of ε identifies that our samples are nonrelaxor. Increasing the Ni concentration increases the value of dielectric constant and the Tc is shifted to lower temperature.

A new hybrid piezoelectric ultrasonic motor with two stators

A new hybrid piezoelectric ultrasonic motor, which consists of one rotor and two stators, was proposed in this paper. In order to match the resonance frequencies of longitudinal vibration and torsional vibration excited in the stators, a symmetrical structure was adopted in design of the motor. A so-called mass matching method, namely adding two rings to the outside circumference of the two stators respectively, was used to adjust the resonance frequencies of these two vibrations. A finite element model was developed using ANSYS software for the purpose of analyzing the resonance frequencies of longitudinal vibration and torsional vibration as well as the function of the adjusting rings. The results show that the resonance frequency of torsional vibration varies with the position of the ring, but the resonance frequency of longitudinal vibration changes little. By means of adjusting the mass and the position of the rings, the first order resonance frequency of longitudinal vibration is coincided with that of torsional vibration and the value is 20.75kHz. An experimental prototype motor was fabricated according to the analytical results and its performance is in agreement with the theoretical predictions. The speed of motor reaches the maximum 92r/min at the working frequency 19.0kHz.

Design and Characterization of a Low-Cost Piezoelectric Vibration Energy Harvester with Bulk PZT Film

To improve the efficiency of MEMS piezoelectric vibration energy harvesters(PVEHs), the bulk lead zirconate titanate(PZT) has been used to substitute the thin film PZT for the higher mechanical-electrical coupling coefficients. The expensive equipment of micromachining set a high entry barrier on the research of PVEHs with high efficiency. To solve this issue, this paper developed an efficient PVEH with bulk PZT using common precision machining, whose dimensions and electrical outputs are comparable to the MEMS devices. After numerically analyzing the effects of the length ratio of the proof mass to the harvester on the output power, a compact PVEH consisting of a cantilevered uni-morph and a tungsten proof mass was designed. Simulations show that the mechanical damping ratio and the thickness have little effects on the optimized length ratio. By using a uni-morph with the copper structural layer of about 80-90μm and the bulk PZT-5 H layer of 139μm, a low-cost harvester prototype was assembled. The key parameters of the prototype were experimentally identified and compared with the theoretical predictions. Under the harmonic base excitation of 0.4 g(where g = 9.8 m/s^2) at 160 Hz, the maximum output power of the prototype is about 76.7μW, with the normalized power density of about 3.35 mW/cm^3/g^2. Under base excitation of 0.4 g at 159 Hz, the prototype charged a 680μF capacitor from 0 to 4.84 V in about 154 seconds.

Preparation,crystallization,microstructure and dielectric properties of lead bismuth titanate borosilicate glass ceramics

Various bulk and transparent glasses were prepared by rapid melt quenching technique in the glass system 55[(Pb_(x)Bi_(1-x))TiO_(3)]-44[2Si_(O)2B_(2)O_(3)]-La2O3(x=0-0.7).The X-ray diffraction(XRD)studies of the glass samples confirmed the amorphous nature.The differential thermal analyses(DTA)were carried out from room temperature to 900℃with a heating rate of 10℃/min.The DTA patterns of the samples showed one or more exothermic sharp peaks shifting towards lower temperature side with increasing concentration of bismuth oxide(BiO).On the basis of DTA results,the solid solution of bismuth titanum oxide(Bi_(2)Ti_(2)O_(7))/lead bismuth titanium oxide(Pb3Bi4Ti6O21)was precipitated in borosilicate glassy matrix as a major phase.The glasses were subjected to 4 h and 8 h heat treatment schedules to convert into glass ceramics.XRD analysis of these glass ceramic samples showed that the major crystalline phase of the entire glass ceramic samples with 0≤x≤0.5 is found to have cubic crystal structure,while it is tetragonal for glass ceramic sample with x=0.7.The scanning electron microscopy(SEM)micrographs indicated the uniform distribution of Bi_(2)Ti_(2)O_(7)and Pb3Bi4Ti6O21 crystallites in the glassy matrix.

Properties of La_2O_3-Doped PNSZT Piezoelectric Ceramics Having Tetragonal and Rhombohedral Coexistent Phases

The relationship between composition and the electric mechanical properties for La2O3-doped lead niobium stibium zirconate titanate(La2O3-doped PNSZT) piezoelectric ceramics,in which there are tetragonal and rhombohedral coexistent phases, was studied. A series of piezoelectric ceramics with good properties was obtained, having dielectric constants (ε= 1500 ~ 2500), plane electromechanical coupling factor(Kp = 0.45 ~ 0.65), mechanical quality factor( Qm = 500 ~ 1600). These materials are used for making ultrasonic sensor and filter, and marine acoustic launching and receiving device, and so on. It has been explored that the influence of composition on the lattice constant and phase composition of La2O3-doped PNSZT piezoelectric ceramics by XRD(X-ray diffraction) . The character of dielectric constant changing of La2O3-doped PNSZT piezoelectric ceramics before polarization and after polarization was studied. The affecting mechanism about composition on the electric machine properties of phase coexistent La2O3-doped PNSZT piezoelectric ceramics was analyzed and discussed.

High visible light photocatalytic activities obtained by integrating g-C_(3)N_(4) with ferroelectric PbTiO_(3)

Graphitic carbon nitride(g-C_(3)N_(4))with the merits of high visible light absorption,proper electronic band structure with high conduction band edge and variable modulation,is viewed as a promising photocatalyst for practical use.To alleviate its high recombination rate of photo-excited charge carriers and maximize the photocatalytic performances,it is paramount to design highly effective transfer channels for photo-excited charge carriers.Ferroelectric materials can have the charge carriers transport in opposite directions owing to the internal spontaneous polarization,which may be suitable for constructing the heterostructure with g-C_(3)N_(4)for efficient charge separation.Inspired by this concept,herein ferroelectric PbTiO_(3),which can be the visible-light absorber,is coupled with g-C_(3)N_(4)to construct PbTiO_(3)/g-C_(3)N_(4)heterostructure with close contact via Pb–N bond by the facile post thermal treatment.The optimized Pb TiO_(3)/g-C_(3)N_(4)heterostructure exhibited excellent photocatalytic and photoelectrochemical activities under visible light irradiation.Moreover,the simultaneous application of ultrasound-induced mechanical waves can further improve its photocatalytic activities through reinforcing the built-in piezoelectric field.This work proposes a widely applicable strategy for the fabrication of high-performance ferroelectric based photocatalysts and also provides some new ideas for developing the understanding of ferroelectric photocatalysis.

The effects of N-doping and oxygen vacancy on the electronic structure and conductivity of PbTiO_3

By using spin-polarized density functional theory calculations, the electron density differences, band structures and density of states of p-type N-doped PbTiO3 have been studied. In addition, the oxygen vacancy in N-doped PbTiO3 is also discussed. After the nitrogen dopant is introduced into the crystal, the N-doped PbTiO3 system is spin-polarized, the spin-down valance bands move to a high energy level and the Fermi energy level moves to the top of the valance bands, finally the band gap is narrowed. In this process, the N-doped PbTiO3 shows typical p-type semiconductor characteristics. When an oxygen vacancy and N impurity coexist in PbTiO3, there is no spin-polarized phenomenon. The conduction bands move downward and the acceptors are found to be fully compensated. The calculation results are mostly consistent with the experimental data.