PT Thick Films Research Articles

Ferroelectric and piezoelectric properties of BaTiO3-templated 0.36BiScO3-0.64PbTiO3 thick films for piezoelectric device applications

ABSTRACT A novel 0.36BiScO3-0.64PbTiO3 (0.36BS-0.64PT) textured ceramic was developed using plate-like BaTiO3 (BT) templates for high temperature piezoelectric device applications. Sintering temperature and amount of BT template played important roles in improving the density, crystal orientation, and ferroelectric and piezoelectric properties of the BT-templated 0.36BS-0.64PT thick films. When sintered at 1000°C, highly dense BS-PT textured films were obtained without formation of a secondary phase. The increased amount of BT template facilitated the degree of texture but deteriorated the relative density of BS-PT thick film. In particular, enhanced ferroelectric and piezoelectric properties were obtained for 1 vol% BT-templated 0.36BS-0.64PT thick film sintered at 1000°C; this film exhibited the very large Pr (44.2 μC/cm2 at 4 kV/mm), d33 (444 pC/N), kp (57.4%), and g33 (36 × 10−3Vm/N) values. In addition, considering the inverse relation between TC and strain, the electrostrain of d33* (622 pm/V at 4 kV/mm) was excellent, showing potential for piezoelectric actuator applications.

Artificially induced normal ferroelectric behaviour in aerosol deposited relaxor 65PMN–35PT thick films by interface engineering

A thin dielectric layer of Al2O3was grown by atomic layer deposition on a relaxor ferroelectric 65Pb(Mg1/3Nb2/3)O3–35PbTiO3(PMN–PT)/Pt/Si thick film fabricated by the aerosol deposition technique to artificially induce ferroelectric behaviour.

0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 Thick Films for High-Frequency Piezoelectric Transducer Applications

The properties of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (0.65PMN–0.35PT) thick films were studied for high-frequency piezoelectric transducer applications. The films were prepared by screen-printing a thick-film paste on platinized alumina substrates and subsequent sintering at 950 °C. The effective thickness-coupling factor of these films was close to 48%, which is comparable with bulk ceramics having the same compositions. Furthermore, simulations of two configurations representing one element of a high-frequency linear-array transducer (30 MHz) suggests that 0.65PMN–0.35PT thick-films in 50 Ω electrical matching environment improves the performance in comparison with standard Pb(Zr,Ti)O3 (PZT) compositions.

Sol–gel derived PMN–PT thick films for high frequency ultrasound linear array applications

A 12-µm PMN–PT [0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3] thick film was produced by alternate spin-coating of a ceramic powder/sol–gel composite and infiltration of the sol–gel. Using this technique, a high quality PMN–PT thick film was obtained, showing a permittivity εr of ~3300 and dielectric loss factor of ~0.02 at 1 kHz. Photolithographic and wet etching techniques were used to fabricate a 32-element linear array from the film. The completed array showed a center frequency of approximately 110 MHz and a bandwidth of 60% at −6 dB without a matching layer. The performance of the kerfless array was studied and compared to a kerfed array simulated with finite element analysis.

High-performance PMNߝPT thick films

This article describes some of our work on ₀.₆₅Pb(Mg₁/₃Nb(₂/₃)O₃-₀.₃₅PbTiO₃ (0.65PMN-0.35PT) thick films printed on alumina substrates. These thick films, with the nominal composition ₀.₆₅Pb(Mg₁/₃Nb(₂/₃)O₃-₀.₃₅PbTiO₃, were produced by screen-printing and firing a paste prepared from an organic vehicle and pre-reacted fine particles of avery chemically homogeneous powder. To improve the adhesion of the 0.65PMN-0.35PT to the platinized alumina substrate,a Pb(Zr₀.₅₃Ti₀.₄₇)O₃ layer was deposited between the electrode and the substrate. The samples were then sintered at 950 °C for 2 h with various amounts of packing powder on the alumina (Al₂O₃) substrates. The sintering procedure was optimized to obtain dense 0.65PMN-0.35PT films. The films were then characterized using scanning electron microscopy as well as measurements of the dielectric and piezoelectric constants.The electrostrictive behavior of the 0.65PMN-0.35PT thick films was investigated using an atomic force microscope(AFM). Finally, substrate-free, large-displacement bending type actuators were prepared and characterized, and the normalized displacement (i.e., the displacement per unit length) of the actuators was determined to be 55 μm/cm at 3.6 kV/cm.

Dielectric behavior and phase transition of perovskite PMN–PT films

The dielectric properties of perovskite relaxor ferroelectrics 0.80Pb(Mg1/3Nb2/3)O3–0.20PbTiO3 (0.80PMN–0.20PT) thick films fabricated by electrophoretic deposition were investigated as a function of temperature and frequency. The phase transformation of 0.80PMN–0.20PT thick films has two different kinds of phase transition: one is a diffused phase transition around the temperature of dielectric permittivity maxima and the other is a first-order transition from frequency dispersion relaxor ferroelectrics to normal ferroelectrics. The frequency and temperature dependence of the dielectric permittivity maximum was also analyzed to discuss the physical meaning of the Debey, Vogel–Fulcher (V–F) and new-glass (N-G) relations. It is shown that the N-G relation is more suitable to characterize the relaxation behavior than the Debey and V–F relations.

Influence of the substrate on the phase composition and electrical properties of 0.65PMN–0.35PT thick films

Thick films with the nominal composition 0.65Pb(Mg 1/3Nb 2/3)O 3–0.35PbTiO 3 (0.65PMN–0.35PT) were produced by screen-printing and firing paste prepared from an organic vehicle and pre-reacted powder. The films were fired for 2 h at 950 °C on alumina (Al 2O 3), platinum (Pt), aluminium nitride (AlN) and 0.65PMN–0.35PT substrates. The films were then characterized using scanning electron microscopy, X-ray diffraction and dielectric constant measurements. The X-ray analysis did not detect the presence of any undesirable pyrochlore phase, and the differences in the phase compositions were determined with a Rietveld refinement. The variations of the cell parameters vs. the temperature for the monoclinic and tetragonal phases were calculated. It was demonstrated that under similar processing conditions the microstructures, phase compositions and dielectric properties strongly depended on the stress in the thick films due to the different temperature expansion coefficients of the thick films and the substrates. The 0.65PMN–0.35PT thick films under compressive stresses (for the case of the Al 2O 3 and Pt substrates) exhibited a tetragonal phase in addition to the monoclinic one. The films were sintered to a high density and with a coarse microstructure. These microstructures favour a high dielectric constant. In contrast, for the films under a tensile stress, like the films on AlN substrates, the films were sintered to a lower density and the microstructure consisted of smaller grains. The X-ray analysis showed mainly a monoclinic phase, while the tetragonal phase was not detected. These results indicate the importance of the stresses in 0.65PMN–0.35PT thick films and their influence on the structural and electrical characteristics of the films.

0.65Pb(Mg 1/3Nb 2/3)O 3–0.35PbTiO 3 thick films prepared by electrophoretic deposition from an ethanol-based suspension

We have investigated the processing of 0.65Pb(Mg 1/3Nb 2/3)O 3–0.35PbTiO 3 (denoted PMN–PT) thick films using an electrophoretic deposition process (denoted EPD), with the PMN–PT particles suspended in an ethanol-based suspension. The zeta-potential and the viscosity were measured to identify the conditions for the preparation of a stable suspension suitable for the EPD. The applied voltage, the deposition time, the chemical composition of the suspension and the concentration of the powder were investigated in order to obtain a high-quality PMN–PT deposit with a target thickness of about 50 μm. The PMN–PT thick films prepared from stoichiometric and PbO-excess suspensions by sintering at 950 and 1100 °C were examined by X-ray powder-diffraction analysis and scanning electron microscopy. The highest functional response was obtained for a homogeneous, dense, crack-free PMN–PT thick film prepared from a PMN–PT suspension with excess PbO. The film was deposited at a constant voltage of 10 V and for a time of 120 s, followed by sintering at 1100 °C in a PbO-rich atmosphere. The film's properties were as follows: a dielectric permittivity ɛ of 20,250 at a T m of 172 °C, a remanent polarization of 17 μC/cm 2 and a coercive field of 5 kV/cm.

Relaxor behavior and dielectric properties of lead magnesium niobate–lead titanate thick films prepared by electrophoresis deposition

Lead magnesium niobate–lead titanate (0.80Pb(Mg 1/3Nb 2/3)O 3–0.20PbTiO 3, PMN–PT) thick films on platinum metallic foils were successfully fabricated by electrophoretic deposition (EPD). The room temperature relative dielectric constant and the maximum relative dielectric constant were 4645 and 25,640 at 1 kHz, respectively. The relaxor nature of PMN–PT thick films was studied in terms of diffused phase transition along with frequency dispersion of temperature of dielectric maximum ( T m). Deviation from Curie–Weiss behavior and temperature evolution of the local order parameter were found in the films. The degree of relaxation obtained from the modified Curie–Weiss law strongly suggests the relaxor behavior. Vögel–Fulcher relationship was used to analyze the frequency dependence of temperature of dielectric maximum ( T m).

The electrostrictive effect in ferroelectric 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 thick films

The electromechanical behavior of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (0.65PMN-0.35PT) thick films, screen printed and fired on alumina substrates, was investigated using an atomic force microscope. A quadratic relation between the induced strain and the electric field was found and is discussed here. The electrostrictive coefficient M33 was determined to be 7.6×10−16 m2/V2. The determined tetragonal crystal structure, the frequency independence of the dielectric maxima as a function of temperature, and the hysteresis loop with a remanent polarization of 31 μC/cm2 and a coercive field of 40 kV/cm confirm the ferroelectric nature of the developed 0.65PMN-0.35PT thick films.

Pb(Mg1/3Nb2/3)O3and (1 - x)Pb(Mg1/3Nb2/3)O3- xPbTiO3Relaxor Ferroelectric Thick Films: Processing and Electrical Characterization

The lead magnesium niobate [Pb(Mg1/3Nb2/3)O3 or PMN], and its solid solutions with lead titanate (PbTiO3 or PT), are of great interest because of their high electromechanical properties. At large PMN content, these materials exhibit relaxor characteristics with large electrostrictive strains and a large permittivity, while compositions near the morphotropic phase boundary present very interesting piezoelectric properties. So far, properties of these materials in ceramic, thin film and single-crystal form have been investigated. In this paper, we report on preparation and properties of pyrochlore free PMN and 0.65PMN-0.35PT thick films (thickness = 10 to 20 μm). The films were prepared from ethyl cellulose ink by screen printing on alumina substrate. The influence of various parameters, such as powder characteristics, inks formulation and films sintering conditions, on films densification are discussed. The dielectric and electromechanical properties of the films were examined. Relaxor-like behaviour was clearly demonstrated in PMN films. The maximum relative permittivity for PMN film was 10000 (at 0.1 kHz), which is lower than in bulk ceramics (17800 at 0.1 kHz) prepared under the same conditions. For 0.65PMN-0.35PT, the maximum relative permittivity was around 15500 against 24000 in the bulk. Several parameters, which might be responsible for the lower permittivity, are discussed. Poled 0.65PMN-0.35PT thick films exhibit relatively large piezoelectric response (d 33 up to 200 pm/V) and unipolar strains approaching 0.1%, making these films of interest for various actuator and transducer applications.

STUDY OF PMN-PT THICK FILMS FABRICATED BY SPIN-COATING

Having high dielectric constants and large mechanical strain, relaxor materials are attractive to the application of actuators in electromechanical systems and elements for large and bright display of optical image where the lower operation voltage and larger deformation are required. In this paper, we study the dielectric properties of 0.9PMN-0.1PT thick films fabricated by a spin coating method. The thick film is prepared for the application of large and bright display elements of an optical-image. In this application a layer of PMN-PT is filled in a mold. The thickness of the layer in the device should be in tens or hundreds of micrometers. Therefore, we used spin-coading technique to make PMN-PT thick films. The thickness of the films fabricated with this method ranges from 70mm to 100mm which are suitable to this application. The samples were electroded with silver print and characterized by dielectric constant and loss measurements. The experimental results show that the dielectric loss is less than 2 percent and the dielectric constant is greater than 10 at the room temperature in the frequency ranging from 100Hz to 1.0 MHz. A comparison of the results with those of PZT thick films manufactured with the same method is also presented.