Pb(Mg1/3Nb2/3)O3-xPbTiO3 Research Articles

Deposition and Characterization of Pyroelectric PMN-PT Thin Films for Uncooled Infrared Focal Plane Arrays

Modern uncooled infrared focal plane arrays (UFPA) development is oriented toward silicon microstructure monolithic arrays by employing pyroelectric thin films with continuing trends in high performance and miniaturization. In order to exploit high performance pyroelectric thin films, (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3(PMN-PT) thin films withx= 0.26 were deposited on LaNiO3/Si substrates by the radio-frequency magnetron sputtering technique. (110) preferred orientation thin films with pure perovskite structures were obtained at a substrate temperature of 500°C. The ferroelectric, dielectric and pyroelectric properties of the films were investigated. The films show a typical polarization – electric filed hysteresis loop with a large remnant polarization of 17.2 μC/cm2. At room temperature, the high pyroelectric coefficient of 3.1 × 10-4C/m2K together with low dielectric constant of 470 and loss tangent of 0.04 render the film promising for uncooled infrared device applications. The origin of the differences in electrical properties between the films and bulk materials has also been discussed.

Pb(Mg1/3Nb2/3)O3–PbTiO3(PMN-PT) Material for Actuator Applications

Due to its large piezoelectric and electrostrictive responses to an applied electric field the (1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3(PMN-PT) solid solution has been widely investigated as a promising material for different actuator applications. This paper discusses some of the recent achievements in the field of PMN-PT piezoelectric and electrostrictive actuators manufactured from PMN-PT single crystals, bulk ceramics, or thick films. The functional properties of PMN-PT materials and some representative examples of the investigated PMN-PT actuator structures and their applications are reported.

Technology of Ferroelectric Electron Emission

Electron emission from ferroelectric cathodes is commonly suggested as an electron source for different application due to its special characteristics such as high current density, easy treatment and operation, etc. The technology of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) ferroelectric cathode is introduced in this paper. Stable emission current is obtained from the PMN-PT ferroelectric cathode and the characteristic of ferroelectric electron emission is deal with as well.

The Growth and Properties of Relaxor‐Based Ferroelectric Single Crystals

Much attention is drawn to the fundamental research and the applications of the relaxor‐based ferroelectrics for the next generation of piezoelectric devices. Mass production of Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMNT) and ternary xPb(In1/2Nb1/2)O3–yPb(Mg1/3Nb2/3)O3–zPbTiO3 (PIMNT) single crystals with a Bridgman method was reported. The piezoelectric, pyroelectric, and electric–optical performances of PMNT single crystals are much more excellent than traditional ceramics with the composition near morphotropic phase boundaries. Compared with PMNT crystal, PIMNT crystals can be used in a more broad range of device applications due to their high Curie temperature Tc and large coercive fields Ec. A relaxor‐based Na0.5Bi0.5TiO3–xBaTiO3 (NBBT) crystal grown by the top seeded solution growth method was also investigated to find a lead‐free material with better piezoelectric performance. The properties of these relaxor‐based single crystals were summarized. The mechanism of the enhanced piezoelectric response is discussed, based on the phase transitions induced by the variations of the temperature, pressure, composition, and electric field.

Large signal electromechanical properties of low loss (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 single crystals

The use of single crystals based on the solid solution (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 (PMNT) has been demonstrated in many piezoelectric devices, but the low mechanical quality factor has limited its use in high power projector applications. In this work, 33-mode properties of PMNT single crystals with various modifications were evaluated to see if self-heating may be reduced by decreasing the mechanical and electrical losses within the active material. Three modifications were evaluated: incorporating ternary components, adding acceptor dopants, or orienting the crystal along different crystallographic directions. The electromechanical properties of these modified crystals were evaluated under increasing levels of dynamic strain. The results suggest that modified single crystal PMNT may improve the source level from a projector while reducing thermal effects from self-heating, making them appropriate for high power applications.

Step-down piezoelectric transformer fabricated with (1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 single crystal

In present work, a ring-type unipoled step-down piezoelectric transformer with the dimensions of Phi16x0.7 mm(3) was designed and fabricated using relaxor ferroelectric single crystal (1-x)Pb(Mg(1/3)Nb(2/3))O(3)-xPbTiO(3) (PMN-PT). Both the input and output parts of this transformer were poled along the thickness direction, utilizing the radial vibration mode of PMN-PT. The electrical measurement results indicated that under the matching load resistance of 257 Omega, a voltage transformation ratio of 0.44 was obtained at the resonance frequency of 105 kHz. The frequency and load dependences of this transformer were also systematically studied and discussed. With the input voltage increasing, a maximum output power of about 0.9 W was obtained with the temperature rise less than 5 degrees C. This step-down single-crystal transformer show potential applications in compact-size, small-power ac-dc converters.

Pyroelectric/electrocaloric energy scanvenging and cooling capabilities in ferroelectric materials

Current needs for clean energy sources aroused the problem of energy scavenging. Significant advances have been achieved in the framework of energy harvesting on solar energy, wind and vibrations (mechanical quantities). Different systems are already available: solar cells, electromechanical conversion for harvesting from vibrations or from mechanical stress (i.e. produced by a person walking or an object movement) [1]. Wasted heat is rarely harvested, mainly because of the very low efficiency of harvesting devices and their large consumption. Pyroelectric materials may be used for energy scavenging, due to their ability to convert temperature variations into usable electric energy. The reverse effect of pyroelectric activity is the electrocaloric effect. The electrocaloric effect (ECE) is a general property of dielectrics to change their temperature under applied electric field at adiabatic conditions. When having heat exchange with an outer medium, it defines the exchanged heat as a function of the applied electric field under isothermal conditions. In the case of ferroelectric materials ECE is strongly correlated with the pyroelectric effect, which gives the change of electric induction for a given temperature variation. The ECE effect may be used for refrigeration devices whereas the pyroelectric effect may be used for temperature/heat sensors or energy harvesting. Electrocaloric materials were the focus of significant scientific interest in the 1960s and 1970s, but were not commercially exploited as the electrocaloric effects were insufficient for practical applications [2]. (1-x)Pb(Mg1/3Nb2/3)O3xPbTiO3 (PMN-PT) materials show a quite high pyroelectric and electrocaloric activity [3,4]. However the practical use of such materials is their electric field limitations before electric breakdown. It is in fact limited to 3–5 kV/mm on bulk ceramics, and could be largely increased for fields up to 50–100 kV/mm. Such large electric fields associated with outstanding electrocaloric conversion were obtained on PZT thin films and shown by Mischenko et al. [5] with a predicted controllable temperature of 12 K for 25 V input voltage.

A Vibration-Based PMN-PT Energy Harvester

We report design, modeling, analysis, and experimental study of a vibration-based piezoelectric energy harvester. The energy harvester is made of a composite cantilever of a single crystal relaxor ferroelectric material, (1- x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), and a polydimethylsiloxane (PDMS) base layer. A PDMS proof mass is constructed at the tip of the composite cantilever beam and is used as a means to tune the system natural frequency. The use of the PMN-PT piezoelectric material and an interdigited electrodes (IDEs) design improves the energy conversion efficiency. A dynamic systems modeling approach is employed to analyze the responses and the performance of the harvester design. We have demonstrated that a prototype of the harvester with a size of 7.4 mm times 2 mm times 110 mum outputs a voltage of 10 V (0.3 mW power) under a vibration excitation with a peak-to-peak amplitude of 1 mm at a frequency around 1.3 kHz. Based on the experimental results, the power density prediction of the proposed harvester design shows a superior performance than that of the other reported piezoelectric harvesters.

Preparation and electrical properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 solid solutions

Ceramic samples of lead magnesium niobate (PMN) and (1 − x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 (PMN-PT) solid solutions with x = 0, 0.05, 0.10, and 0.30 have been prepared by solid-state reactions, and their structural, electrical, and piezoelectric properties have been studied using x-ray diffraction, Rietveld profile analysis, impedance spectroscopy, and the resonance/antiresonance method. The results indicate that the use of nonstoichiometric columbite niobates enables the synthesis of phase-pure PMN and PMN-PT.

Fitting and analyzing the dielectric spectra of Pb(Mg1/3Nb2/3)O3-xPbTiO3 ceramics and single crystals

The dielectric spectra of Pb(Mg1/3Nb2/3)O3-xPbTiO3(PMN-xPT) ceramics and single crystals with different PbTiO3(PT) content were fitted and analyzed with dual mechanisms model proposed by Cheng et al. Two polarization processes were proposed in this model, one is related to flips of polar regions and the other associates with the breathing behavior of frozen polar regions. The fitted results showed that the weight factors of contribution of dielectric response from the two mechanisms near T m varied with the different measuring frequency and PT content. These results can explain why the modeling parameters of T m and ω to Vogel–Fulcher relation show unlike results in different frequency regions.

PMN-PT Single Crystal Piezo-Electric Acoustic Sensor

AbstractThe MEMS (micro-electro-mechanical systems) microphone enables the manufacturing of small mechanical components on the surface of a silicon wafer. The MEMS microphones are less susceptible to vibration because of the smaller diaphragm mass and an excellent candidate for chip-scale packaging. In this paper, we present a piezoelectric MEMS microphone based on (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) single crystal diaphragm. The PMN-PT materials exhibit extremely high piezoelectric coefficients and other desirable properties for an acoustic sensor. The piezoelectric-based microphone can offer the ability to passively sense without the power requirements. In particular, this paper introduces the design of a PMN-PT single crystal diaphragm with interdigitated electrode. We were able to fabricate miniaturized PMN-PT single crystal diaphragms. The fabricated sensor exhibits the sensitivity of 1.5mV/Pa. This implies that the PMN-PT thin film microphone has a potential of excellent acoustic characteristics.

The anomalous skin effect in single crystal relaxor ferroelectric PZN- x PT and PMN- x PT

X-ray and neutron scattering studies of the lead-based family of perovskite relaxors Pb(Zn1/3Nb2/3)O3–xPbTiO3 (PZN-xPT) and Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN-xPT) have documented a highly unusual situation in which the near-surface region of a single crystal can exhibit a structure that is different from that of the bulk when cooled to low temperatures. The near-surface region, or “skin” can also display critical behavior that is absent in the crystal interior, as well as a significantly different lattice spacing. By varying the incident photon energy, and thus the effective penetration depth, X-ray measurements indicate a skin thickness of order 10–50 µm for PZN-xPT samples with 0 ≤ x ≤ 8%. Neutron residual stress measurements on a large PMN single crystal reveal a uniform lattice spacing within the bulk, but an increased strain near the surface. The presence of this skin effect has led to incorrect phase diagrams for both the PZN-xPT and PMN-xPT systems and erroneous characterizations of the nature of the relaxor state.

High electric-field-induced strain of Pb(Mg1/3Nb2/3)O 3 -PbTiO 3 crystals and their application in multilayer actuators

Electric-field-induced strain behavior of differently oriented and componential (1-x)Pb(Mg1/3Nb2/3)O3xPbTiO3 (PMNT) crystals was investigated. An optimum composition range (29%≤x≤31%) of 〈001〉-oriented PMNT crystals was ascertained for multilayer actuator applications, which exhibited high-strain and low-hysteresis behavior. The rhombohedral (monoclinic)–tetragonal phase-transition behavior in PMNT single crystals is dependent on their thermal and electric history, which markedly impacts on the strain performance of the crystals. In contrast to PZT-SF (doped PZT ceramics) multilayer actuators, the strain values for 20-layer PMNT actuators with individual element sizes of 6×6×0.3 mm3 are larger by more than five times at 20 kV/cm (0.373% compared to 0.072%), and 23-μm displacements can been achieved. Against 40-N load, the displacements are decreased to 20.2 μm.

High electric-field-induced strain beahvior of single-crystal Pb(Mg1/3Nb2/3)O3-xPbTiO3 multilayer piezoelectric actuators

Two 10-mm-long multilayer prototype actuators were fabricated by a stack method using 55 pieces of 5 mm×5 mm×0.15 mm Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMNT) single crystals and PZT-5A ceramics, respectively. The strain values for PMNT multilayer piezoelectric actuators are twice those of PZT-5A multilayer actuators, and 20.8-µm displacements can be achieved at the same E-field of 15 kV/cm. Although thermal and electrical history markedly impact dielectric and piezoelectric performance of PMNT crystals, the PMNT multilayer actuator can still achieve large displacements with approximately linear behavior below 60°C. Broad stable dynamic displacement characteristic and fast displacement response make the new-type actuators promising candidates for the application in new-generation high-performance solid-state actuators.

Cooling-Rate-Dependent Domain Structures of Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals Observed by Contact Resonance Piezoresponse Force Microscopy

The domain structures of (001) plates of (1–x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) single crystals were observed at room temperature after 240°C thermal treatment at various cooling rates. The starting composition of the PMN-PT single crystals was x=0.32; the dielectric constant of the single crystals exhibited a maximum at 153°C. Contact resonance piezoresponse force microscopy (CR-PFM) was utilized for domain imaging, because microdomain images could be obtained without domain structure degeneration. The average size of domains strongly depended on the cooling rate. The obtained domain images were approximately fingerprint patterned on a micron scale, but were fragmented by circular domains on a submicron scale. These finer circular domain structures were probably microdomains that existed in the relaxor phase and were subsequently quenched during the relaxor-to-ferroelectric phase transition.

Growth and observation of domain structure of Lead Magnesium Niobate–Lead Titanate Single Crystals

(1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 (PMNT) single crystals were grown by the vertical Bridgman method, and the spatial domain configurations in the rhombohedral and tetragonal crystals were observed using a polarizing microscope, SEM, and SFM in piezo response mode. In the rhombohedral crystals, both regular tire-track patterns and irregular fingerprint patterns were observed on the as-grown crystal plates. The tire-track patterns were composed of {100} and {110} domain walls. The irregular fingerprint patterns were antiparallel domains. In the tetragonal crystals, 3 different types of etching areas were observed. These patterns consisted of 180° domains and 90° {110} domain boundary.

Phase diagram of the ferroelectric relaxor(1−x)PbMg1/3Nb2/3O3−xPbTiO3

Synchrotron x-ray powder diffraction measurements have been performed on unpoled ceramic samples of (1-x)PbMg(1/3)Nb(2/3)O3-xPbTiO3 (PMN-xPT) with 30%<= x<= 39% as a function of temperature around the morphotropic phase boundary (MPB), which is the line separating the rhombohedral and tetragonal phases in the phase diagram. The experiments have revealed very interesting features previously unknown in this or related systems. The sharp and well-defined diffraction profiles observed at high and intermediate temperatures in the cubic and tetragonal phases, respectively, are in contrast to the broad features encountered at low temperatures. These peculiar characteristics, which are associated with the monoclinic phase of MC-type previously reported by Kiat et al and Singh et al., can only be interpreted as multiple coexisting structures with MC as the major component. An analysis of the diffraction profiles has allowed us to properly characterize the PMN-xPT phase diagram and to determine the stability region of the monoclinic phase, which extends from x= 31% to x= 37% at 20 K. The complex lansdcape of observed phases points to an energy balance between the different PMN-xPT phases which is intrinsically much more delicate than that of related systems such as PbZr(1-x)TixO3 or (1-x)PbZn(1/3)Nb(1/3)O3-xPbTiO3. These observations are in good accord with an optical study of x= 33% by Xu et al., who observed monoclinic domains with several different polar directions coexisting with rhombohedral domains, in the same single crystal.

Study of phase transitions of single crystals of PMN-PT solid solutions

Two compositions of (1−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) (x=24 and 35) single crystals were studied by means of dielectric and pyroelectric measurements and domain observations. The results show that the 76/24 crystals exhibit relaxor feature with field induced transition like behavior. Whereas for the composition 65/35, when T< Tm the sample behaves as a normal ferroelectric; when T>Tm the temperature dependence of σ obeys the Smolenskii's relation rather than Curie-Wiss law, indicating the anomalous feature of the transition. The results were discussed from the point of view of random fields.

Preparation of PMN-PT films by laser ablation method

Lead magnesium niobate titanate, (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) thin films have been prepared on MgO substrate, Pt sheet and Si wafers at low temperatures of 450∼600°C by laser ablation method. PMN-PT thin films have preferential orientation of a-axis on MgO(100) and have (100), (200) and (110) orientations on Pt. Surface morphology of PMN-PT films on MgO has the spherical grain of size 100∼150nm. The leakage current of 500nm-thick 0.9PMN-0.1 PT film is not so small still, and about 10×5 A/cm2 at 2 V. Dielectric constants of 0.9 PMN-0.1 PT and 0.6 PMN-0.4 PT thin films are about 1,280 and 940 at 1 MHz and room temperature, respectively.

Continuity in Phase Transition Behavior between Normal and Diffuse Phase Transitions in Complex Perovskite Compounds

The phase transition behavior in the systems of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) and 0.99Pb1-yLa2y/3TiO3-0.01MnO2 (PLT) relaxor ferroelectrics has been investigated to explore the nature of diffused phase transitions (DPT) in these materials. All the dielectric constant (ε)-temperature (T) characteristics for these materials above the Curie point have been found to be described by the equation (1/ε-1/εm)1/n=(T-Tm)/C′, where εm is the maximum dielectric constant of a material, Tm is the temperature giving εm, and n and C′ are constants changing with composition. In the system PMN-PT, the value of n was found to change continuously from 1.0 for PT to 2.0 for PMN without any irregularity. The value of n for the materials of the system PLT also shows a similar variation with La content, and moreover, two C′ versus Tm plots obtained for the two systems PMN-PT and PLT show substantially the same behavior. The nature of DPT is considered to be closely connected with compositional and structural variations, which determine the spatial size and morphology of ferroelectric domains below the Curie point.