Showing papers on "Ferroelectric ceramics published in 1999"

Ferroelectric ceramics : History and technology

Abstract: Ferroelectric ceramics were born in the early 1940s with the discovery of the phenomenon of ferroelectricity as the source of the unusually high dielectric constant in ceramic barium titanate capacitors. Since that time, they have been the heart and soul of several multibillion dollar industries, ranging from high-dielectric-constant capacitors to later developments in piezoelectric transducers, positive temperature coefficient devices, and electrooptic light valves. Materials based on two compositional systems, barium titanate and lead zirconate titanate, have dominated the field throughout their history. The more recent developments in the field of ferroelectric ceramics, such as medical ultrasonic composites, high-displacement piezoelectric actuators (Moonies, RAINBOWS), photostrictors, and thin and thick films for piezoelectric and integrated-circuit applications have served to keep the industry young amidst its growing maturity. Various ceramic formulations, their form (bulk, films), fabrication, function (properties), and future are described in relation to their ferroelectric nature and specific areas of application.

A monoclinic ferroelectric phase in the pb(zr1-xtix)o3 solid solution

Abstract: A previously unreported ferroelectric phase has been discovered in a highly homogeneous sample of PbZr0.52Ti0.48O3 by high-resolution synchrotron x-ray powder diffraction measurements. At ambient temperature the sample has tetragonal symmetry (at=4.037 A, ct=4.138 A), and transforms below ∼250 K into a phase which, unexpectedly, has monoclinic symmetry (am=5.717 A, bm=5.703 A, cm=4.143 A, β=90.53°, at 20 K). The intensity data strongly indicate that the polar axis lies in the monoclinic ac plane close to the pseudocubic [111] direction, which would be an example of the species m3m(12)A2Fm predicted on symmetry grounds by Shuvalov.

Electrical and structural characteristics of lanthanum-doped barium titanate ceramics

Abstract: Single phase La-doped BaTiO3 with the formula Ba1−xLaxTi1−x/4O3: 0⩽x⩽0.20 was prepared by solid state reaction of oxide mixtures at 1350 °C, 3 days, in O2. The tetragonal distortion in undoped BaTiO3 decreased with x and samples were cubic for x⩾0.05. Both the tetragonal/cubic and orthorhombic/tetragonal transition temperatures decreased with x, but at different rates, and appeared to coalesce at x∼0.08. The value of the permittivity maximum at the tetragonal/cubic phase transition in ceramic samples increased from ∼10 000 for x=0 at 130 °C to ∼25 000 for x=0.06 at ∼−9 °C. At larger x, the permittivity maximum broadened, showed “relaxor”-type frequency dependent permittivity characteristics and continued to move to lower temperatures. Samples fired in O2 were insulating and showed no signs of donor doping whereas air-fired samples were semiconducting, attributable to oxygen loss.

A Raman and dielectric study of ferroelectric ceramics

Abstract: Dielectric and Raman scattering experiments were performed on various ceramics with composition Ba(Ti1-xZrx)O3. Such lead-free, environmental-friendly materials were shown, from dielectric measurements, to exhibit behaviours extending from conventional to relaxor ferroelectrics on increasing the zirconium concentration. The evolution of the Raman spectra was studied as a function of temperature for various compositions, and the spectroscopic signature of the corresponding phases was determined. In the relaxor state, the variation of the integrated intensity of the Raman lines with temperature showed a plateau at low temperature. This anomaly was also detected as a peak in depolarization current measurements, and attributed to ergodicity breaking which characterizes usual relaxor systems. Raman results hint at locally rhombohedral polar nanoregions resulting from the random fields associated with Zr ions.

Differences in nature of defects between SrBi2Ta2O9 and Bi4Ti3O12

Abstract: X-ray photoemission spectroscopy measurements were executed to compare the nature of defects in SrBi2Ta2O9 (SBT) and Bi4Ti3O12 (BTO) films. In the SBT film, it was found that the oxygen ions at the metal–oxygen octahedra were much more stable than those at the Bi2O2 layers. On the other hand, for the BTO film, oxygen vacancies could be induced both at the titanium–oxygen octahedra and at the Bi2O2 layers. We suggested that the difference in stability of the metal–oxygen octahedra should be related to different fatigue behaviors of the SBT and the BTO films.

Piezoelectric Properties of Bismuth Layer-Structured Ferroelectric Ceramics with a Preferred Orientation Processed by the Reactive Templated Grain Growth Method

Abstract: Dense CaBi4Ti4O15 (CBT) and Na0.475Ca0.05Bi4.475Ti4O15 (NCBT) ceramics with a highly preferred {001} orientation were prepared by the reactive templated grain growth (RTGG) method. Plate-like Bi4Ti3O12 (BIT) particles were synthesized by a molten salt technique and used as the reactive template. The template particles were mixed with other oxide and carbonate powders and aligned by tape-casting. During the sintering, oriented CBT and NCBT were formed in situ topotaxially on the oriented BIT particles, and textured CBT and NCBT ceramics were eventually fabricated by the templated grain growth and densification. The Lotgering {001} orientation degree of the textured ceramics exceeded 90% for secondary-laminate sintered specimens. Textured CBT and NCBT ceramics poled in the perpendicular direction to the preferred axis exhibited electromechanical coupling coefficient (k33) and piezoelectric coefficients (d33 and g33) three times higher than the values for nontextured ceramics with the same composition.

Ferroelectric behavior of Li-doped ZnO thin films on Si(100) by pulsed laser deposition

Abstract: Thin films of Li-doped ZnO of different compositions (Zn1−xLix)O, x=0.1, 0.17, and 0.3 have been prepared on Si(100) substrates, with no buffer layer, by the pulsed laser deposition method. Ferroelectric behavior with a memory window of 1.2 V has been observed in capacitance–voltage measurements. The peak maximum in the capacitance–temperature curve suggests that the ferroelectric phase transition occurs around 340 K.

Nanoscale reconstruction of surface crystallography from three-dimensional polarization distribution in ferroelectric barium-titanate ceramics

Abstract: The three-dimensional orientation of polarization vectors at the surface of ferroelectric barium–titanate (BaTiO3) ceramics is evaluated using voltage-modulated scanning force microscopy (SFM). By applying an ac voltage to the conductive SFM tip, we measure the relative amount of the three orthogonal components Px, Py, and Pz, of the polarization vector at any surface point. The measured polarization orientation together with the actual domain-wall orientation allows a precise reconstruction of the crystallographic orientation of the investigated grains down to a 40 nm resolution. Excellent agreement is obtained when comparing this orientation with the crystallographic reconstruction revealed by etch patterns from the sample surface topography. We show that the surface topography manifests a domain structure, which was present in the past, while the actual ferroelectric domain configuration is revealed by the modulation technique.

Enhanced ferroelectric properties and lowered processing temperatures of strontium bismuth niobates with vanadium doping

Abstract: This letter reports on enhanced ferroelectric properties and lowered processing temperatures of a SrBi2(V, Nb)2O9 system with vanadium doping. The samples were prepared by reaction sintering of powder mixtures of constituent oxides. With partial substitution of niobium by vanadium cations (up to 10 at. %), the single-phase layered perovskite structure was preserved and the sintering temperature of the system was significantly lowered (∼ 200 °C). The incorporation of vanadium into the layered perovskite structure resulted in a shift of the Curie point to higher temperatures, from 435 to 457 °C with 10 at. % vanadium doping, and an increase in dielectric constant, from ∼700 to ∼1200 with 5 at. % vanadium doping, at their respective Curie points. Both enhanced Curie temperatures and dielectric constants at the Curie points indicate an increase in polarizability, which could be attributed to the increased “rattling space” due to the incorporation of much smaller vanadium cations. Further measurements also revealed that loss tangent of vanadium doped layered perovskites was the same as that without vanadium doping.This letter reports on enhanced ferroelectric properties and lowered processing temperatures of a SrBi2(V, Nb)2O9 system with vanadium doping. The samples were prepared by reaction sintering of powder mixtures of constituent oxides. With partial substitution of niobium by vanadium cations (up to 10 at. %), the single-phase layered perovskite structure was preserved and the sintering temperature of the system was significantly lowered (∼ 200 °C). The incorporation of vanadium into the layered perovskite structure resulted in a shift of the Curie point to higher temperatures, from 435 to 457 °C with 10 at. % vanadium doping, and an increase in dielectric constant, from ∼700 to ∼1200 with 5 at. % vanadium doping, at their respective Curie points. Both enhanced Curie temperatures and dielectric constants at the Curie points indicate an increase in polarizability, which could be attributed to the increased “rattling space” due to the incorporation of much smaller vanadium cations. Further measurements also rev...

Microwave processing and properties of ceramics with different dielectric loss

Abstract: Microwave sintering behaviors of three kinds of ceramics with different dielectric loss [Al 2 O 3 , Ce–Y–ZrO 2 and lead-based relaxor ferroelectrics (PMZNT)] in 2·45 GHz microwave furnace were described. Measurement of sample densities showed an enhancement of the sintering processing for all materials studied. For PMZNT and Ce–Y–ZrO 2 with high dipolar loss or ionic conductive loss, the associated microstructure examined using scanning electron microscopy showed that microwave-sintered compacts produced much finer grain sizes at near theoretical density compared to conventional sintering. Resulting material properties, such as flexure strength and breakdown strength, were also increased due to developed microstructure in microwave processing. However, a comparable grain size and properties were observed for high pure Al 2 O 3 with low dielectric loss in microwave and conventional methods. ©

A phenomenological constitutive law for the behaviour of ferroelectric ceramics

Abstract: A general thermodynamic structure for the constitutive behaviour of ferroelectric ceramics with the Perovskite structure is described. The state of the material is described in terms of the remanent strain and the remanent polarisation. A yield function is identified, such that changes in remanent strain and polarisation can only occur when the yield condition is satisfied. Simple forms of the Helmholtz free energy are presented, based on an understanding of the underlying micromechanical processes. The resulting hysteresis and butterfly loops predicted by this model are in good agreement with the general form of loops observed experimentally.

Cyclic fatigue due to electric loading in ferroelectric ceramics

Abstract: Mechanical fatigue of ferroelectric ceramics due to bipolar cyclic electric loading is examined. Beam specimens out of three different PZT materials were cut and precracks were initiated by Vickers indentation. The specimens were loaded by alternating electric fields varied from 0·9 to 1·0 and 1·5 times the coercive field Ec. In short intervals the crack propagation was measured. Before and after fatigue experiments electric polarisation and strain were measured as a function of the electric field. The crack growth rate decreases with increasing cycle number, and a saturation point is reached after approximately 105 cycles. A correlation between growth rates and ferroelectric strain was detected. Measured strain loops suggest that switching of ferroelectric domains undergoes a strong fatigue effect. Therefore after 106 cycles the elastic strain is not as strong a driving force for further crack extension. In addition fatigue-crack growth is strongly dependent on the material and the electric field strength.

Influence of the electric field on vickers indentation crack growth in BaTiO3

Abstract: In this study, the Vickers indentation method was used to determine the crack growth of ferroelectric barium titanate (BaTiO3) ceramic under the influence of electric fields. It was verified that an applied electric field induces distinct anisotropic crack growth parallel and perpendicular to the poling direction which is mainly interpreted as an anisotropy in fracture toughness. The curve of the measured crack lengths as a function of the applied electric field shows similarity with the strain hysteresis. Curves of cracks parallel and perpendicular to the electric field direction are symmetric to each other. Stress-induced ferroelastic domain switching is used to explain the observed crack lengths anisotropy and change in fracture toughness.

Piezoelectric properties of some lead-free ferroelectric ceramics

Abstract: The use of lead-free materials in piezoelectric ceramics has recently become a very important issue in environmental protection of the earth. Some lead-free piezoelectric materials, namely bismuth sodium titanate, (Bi1/2Na1/2)TiO3 (BNT) – based solid solution ceramics, such as (1-a)BNT-a·BaTiO3 [BNBT], (1-b)BNT-b·NaNbO3 [BNTN] and a(Bi1/2Na1/2)TiO3-b KNbO3-c 1/2(Bi2O3·Sc2O3) [KTNS] (a+b+c=1) systems, were studied for their dielectric, ferroelectric and piezoelectric properties as candidates for a new family of lead-free piezoelectric ceramics. The electromechanical coupling factor, k 33 in the longitudinal mode was found to be 0.55, 0.43 and 0.47 for BNBT-6. BNTN-3 and KTNS, respectively. On particular, the amount of modified Bi3+ ions has an effect on k 33. Consequently these ceramics are potential candidates as lead-free piezoelectric ceramics.

Nonlinear electric-mechanical behavior of a soft PZT-51 ferroelectric ceramic

Abstract: In this investigation, the electric-mechanical response of a PZT ferroelectric ceramic subjected to the combined electric-mechanical loads was experimentally observed. The effect of different compressive stress levels on the electromechanical response was examined. The stress-strain relationship was also measured. The ceramic sample was isolated from the test frame and the high voltage arcing were prevented effectively in the setup which promotes the precise measurement and makes the systemic experimental results available. With a high voltage amplifier and a servo-hydraulic test frame, the butterfly shaped strain vs. electric field curves and the electric displacement vs. electric field hysteresis loops of a soft PZT ceramic at different compressive stress levels were measured. The results show that the electric-mechanical coupled properties of the PZT ceramic are the function of the compressive stress. The switching criteria are given to account for the experimental results and to analyze the nonlinear electric-mechanical behavior relative to the domain switching process in this paper.

A constitutive model for ferroelectric PZT ceramics under uniaxial loading

Abstract: Our aim is the presentation of a macroscopic constitutive model for the purpose of engineering reliability analysis of piezoceramic components designed for so-called `smart' electromechanical sensor and actuator applications. Typically, such components are made of materials like ferroelectric lead zirconate titanate ceramics which exhibit significant history-dependent nonlinearities such as the well known dielectric, butterfly and ferroelastic hystereses due to switching processes. Furthermore, phase transitions lead to distinct thermo-electromechanical coupling properties and rate effects are present. In a first step, we propose a constitutive framework capable of representing general thermo-electromechanical processes. This framework makes use of internal variables and is thermodynamically consistent with the Clausius-Duhem inequality for all admissible processes. Next, we focus on uniaxial electromechanical loadings and introduce microscopically motivated internal variables and their evolution equations. In order to verify the underlying a priori assumptions, we discuss extensively the numerically calculated model response to standard electromechanical loading paths. It turns out that the model represents the typical hystereses mentioned above as well as mechanical depolarization and other nonlinear electromechanical coupling phenomena. Furthermore, the model response exhibits rate effects.

High field dielectric properties of ferroelectric ceramics

Abstract: The dielectric properties of PZT and barium titanate based ferroelectric ceramics have been determined over a wide range of electric field strength (0.05 to 4.0 kV mm−1) by analysis of P-E (polarisation-electric field) hysteresis data. Three different types of dielectric behaviour were identified, depending on the applied field amplitude E 0. In the ‘low field’ region, below a material-dependent threshold field E t, a nearly constant or weakly field-dependent permittivity was obtained, which was attributed to a combination of the intrinsic (ionic) response with a contribution from reversible domain wall vibration. For field levels between E t and the coercive field E c, a linear ϵr′-E 0 relationship was found, which is analogous to the Rayleigh Law in ferromagnetic materials. This behaviour was explained in terms of large scale ferroelectric domain wall translation about an equilibrium domain wall position. For E 0>E c, sharp increases in ϵr′ and ϵr″ occurred as a result of hysteretic ferroelectr...

Effect of poling procedure on the properties of lead zirconate titanate/vinylidene fluoride-trifluoroethylene composites

Abstract: Lead zirconate titanate/vinylidene fluoride-trifluoroethylene [PZT/P(VDF-TrFE)] 0–3 composites for pyroelectric sensor and piezoelectric transducer applications have been fabricated by incorporating PZT powder into a P(VDF-TrFE) copolymer matrix. The properties of these composites can be tailored to suit designated applications by varying the ceramic volume fraction and by using different poling procedures. As both phases in the composite are ferroelectric, and the piezoelectric coefficients of the ceramic and copolymer phases have opposite signs while the pyroelectric coefficients have like signs, special ways can be used to produce three groups of samples with (1) only the ceramic phase poled, (2) two phases poled in the same direction to achieve reinforced pyroelectric activity and reduced piezoelectric activity, and (3) two phases poled in opposite directions to obtain reinforced piezoelectric activity and reduced pyroelectric activity. In this work, original experimental results on the properties of ...

Rayleigh behaviour and the threshold field in ferroelectric ceramics

Abstract: The threshold field, Et, values for various barium titanate and PZT-based ceramics have been determined by examination of the er |-E 0 and er ∥-E 0 relationships. The results obtained for both ‘soft’ and ’hard’ PZT ceramics gave a good fit to the Rayleigh Law over a wide range of field amplitude for E 0 E t. The linear increases in er | and er ∥ as a function of field amplitude were attributed to a lossy ferroelectric domain wall translation mechanism, by analogy with similar behaviour in ferromagnetic materials. At high field levels approaching the coercive field, E c, the measured er |-E 0 and er ∥-E 0 curves deviated from a linear relationship due to the onset of partial ferroelectric domain switching. Pure and Mn-doped barium titanate ceramics exhibited nonlinear er |-E 0 and er ∥-E 0 plots with a gradually increasing gradient. However, all of the materials studied yielded a linear er | and er ∥ relationship, from which a critical field for the initiation of ferroelectric domain switching, E ...

The induced phase transformation and oxygen vacancy relaxation in La-modified bismuth titanate ceramics

Abstract: Nanopowders of Bi2Ti2O7 with various La modifications were fabricated by chemical coprecipitation. As sintered at high temperature, the phase structure in powders translates into (La0.22Bi0.78)4Ti3O12 and (La0.26Bi0.74)2Ti4O11 with increasing La concentration, respectively. Dielectric and nonlinear resistivity investigations in bulk ceramics show that oxygen vacancy relaxation or defect dipole polarization contributes considerably to the dielectric permittivity, while the mechanism is shut off under a threshold field dependent on phase transition as well as temperature. Furthermore, the quantitative analysis of x-ray photoelectron spectroscopy indicates the deviation of oxygen element composition at surfaces of (La0.22Bi0.78)4Ti3O12 ceramic grains from the standard ratio.

Irreversibility of the antiferroelectric to ferroelectric phase transition in (Pb0.90Ba0.10)ZrO3 ceramics

Abstract: Dielectric and x-ray diffraction evidences are presented to show that the antiferroelectric to ferroelectric phase transition in (Pb090Ba010)ZrO3 ceramics is not reversible during the cooling cycle It is shown that the stable antiferroelectric phase recovers from the metastable ferroelectric matrix on aging at room temperature The kinetics of recovery of the antiferroelectric phase is very sluggish It is pointed out that this type of irreversibility occurs in field induced antiferroelectric to ferroelectric transitions also This may have serious implications for the actuator applications of these materials It is proposed that the large transformation strains associated with the antiferroelectric orthorhombic to ferroelectric rhombohedral phase transition is responsible for this irreversibility

Conducting cracks in a piezoelectric ceramic of limited electrical polarization

Abstract: Recent studies show that dielectric nonlinearity (especially the electrical polarization saturation) plays an essential role in the description of crack tip behavior of ferroelectric/piezoelectric ceramics. This paper studies conducting cracks in a poled ferroelectric of limited electrical polarization based on a strip-saturation model of the Dugdale-type. The resulting mixed boundary value problem is analysed and complete solution or exact near tip field is obtained for conducting cracks parallel or perpendicular to the poling axis. It is found that pure electric-field loading applied parallel to the poling axis does not induce any stress intensity factor at conducting cracks. This conclusion distinguishes conducting cracks in a poled ferroelectric from insulating cracks for which the strip-saturation model predicts an electrically induced stress intensity factor. Due to its practical importance, the conducting crack parallel to the poling axis is discussed in more detail. The results indicate that the driving force predicted by the strip-saturation model is lower than that given by the linear piezoelectric model for a conducting crack parallel to the poling axis.

Synthesis and sintering improvement of Aurivillius type structure ferroelectric ceramics by mechanochemical activation

Abstract: An oxide mixture of composition 3Bi 2 O 3 :Nb 2 O 5 :2TiO 2 has been mechanochemically activated in a laboratory mill for different times from 3 to 336 h. The as-milled powder and an unmilled mixture of identical composition were annealed at different temperatures up to the formation of the Aurivillius-type oxide Bi 3 NbTiO 9 , and examined by X-ray diffraction (XRD) and differential thermal analysis (DTA). The sample milled for 336 h shows complete amorphization. Its DTA curve exhibits two exothermic process at 370 and 560°C, corresponding to the formation of a metastable fluorite phase and the Aurivillius-type oxide, respectively. The crystallization temperature of this Aurivillius phase from the unmilled oxide mixture is reported to be 1050°C, whereas from the amorphous powder obtained by 336 h of mechanochemical activation this temperature becomes as low as 600°C. Ceramics of this composition must be prepared by hot-pressing in order to obtain low porosities, owing to the lamellar morphology of the conventionally crystallized powder, which gives rise to textured anisotropic materials. Non-textured ceramics were obtained both from the conventionally crystallized and the amorphous powder by natural sintering at 1100°C. Ceramics obtained from amorphous powder show lower porosity and higher electromechanical coupling factors.

Oxide electrodes as barriers to hydrogen damage of Pb(Zr,Ti)O3-based ferroelectric capacitors

Abstract: The ferroelectric properties of Pb(Zr,Ti)O3 films are known to degrade when subjected to forming gas anneals. In an earlier publication we established that although there may be loss of oxygen and lead during forming gas anneal, the primary mechanism for loss of ferroelectricity is the incorporation of hydrogen and subsequent formation of [OH]−1 bonds between the ionized hydrogen and oxygen ions along the polarization axis in the octahedra. In this study, we show that (La,Sr)CoO3 oxide electrodes can act as a diffusion barrier to hydrogen during forming gas anneals. Forming gas anneal at lower temperatures such as 200 and 300 °C does not lead to a measurable loss of polarization. There is some loss of polarization during forming gas anneals at 450 °C for 12 h, however the capacitors still exhibit ferroelectric properties. The capacitors show no fatigue up to 1011 cycles, no imprint, good logic state retention characteristics, and similar slopes for the pulse width dependent polarization values before and ...

Processing and characterization of high Qm ferroelectric ceramics

Abstract: Use of ferroelectric ceramics in applications like piezoelectric transformers was made possible by the development of new materials with high electromechanical coupling coefficients and high mechanical quality factor. “Hard’’ ferroelectric ceramics of complex composition based on lead zirconate titanate with Nb, Mg, Mn and Li additives have been prepared. The perovskitic phase was produced by solid phase reaction of the oxides. The crucial role played by the intermediate mixing and grinding procedures in the assessment of the final properties of the material was investigated. Densification up to approximately the theoretical density value was achieved. The polarization was obtained by subjecting the samples at 30 kV cm−1 poling electric field, in a silicon oil bath heated at 120°C. Their structural and morphological properties were checked by X-ray diffraction analysis and scanning electron microscopy. Ferroelectric and piezoelectric properties were determined in agreement with IEEE measurement standards. The optimized samples presented very high quality and electromechanical coupling factors, together with small dielectric loss.

Dielectric characterization of polycrystalline Sr2Bi4Ti5O18

Abstract: Five layered Sr2Bi4Ti5O18 has been prepared in the ceramic form with a view to studying its electrical properties. X-ray and microstructural studies were employed for physical characterization. Detailed electrical property measurements were undertaken so as to understand the basic transport physics of this compound. The results of dielectric studies, dc conductivity, and ac impedance are discussed, and a defect formula for Sr2Bi4Ti5O18 has been proposed. The investigations on this material at high temperatures and frequencies reveal its stable behavior.

Fatigue crack growth in ferroelectric ceramics below the coercive field

Abstract: Perovskite-type ferroelectric ceramics have found many applications in actuators, sensors and memories. One critical limitation on their performance is due to electric fatigue, which refers to the deterioration of material properties associated with electric cycling. The degradation of electrical properties in ferroelectrics, which appears in the hysteresis loop in the form of a decrease of remanant polarization and an increase of the coercive field, is a serious concern in application [1]. Due to a strong electro-mechanical coupling effect, an electrical field may also degrade the mechanical properties of ferroelectrics. The performance of ferroelectric ceramics in smart structures is often hampered by the cracks propagating in the devices [2]. It is essential to characterize the failure behavior of ferroelectric ceramics when subjected to a cyclic electric field. Cao and Evans [3] first attacked the issue of electrical field– induced fatigue crack growth. They reported that the growth of indented cracks was governed by the magnitude of an applied electrical field Ea relative to the coercive field Ec: When Ea≤ 0.9Ec, there was only a minor amount of growth (about 50 μm), and then the crack arrested; when Ea≥ 1.1Ec, the crack continued to grow and settled into a steadily growing state. They concluded that the fatigue effect occurred only at fields above the coercive field. For Ea

Dielectric properties of pulsed laser deposited films of PbMg1/3Nb2/3–PbTiO3 and PbSc1/2Nb1/2O3–PbTiO3 relaxor ferroelectrics

Abstract: Highly oriented perovskite films of PbMg1/3Nb2/3–PbTiO3 and PbSc1/2Nb1/2O3–PbTiO3 with compositions near the morphotropic phase boundary were formed by pulsed laser deposition on La0.5Sr0.5CoO3/MgO (100). The dielectric properties of the films were studied over the frequency range of 100 Hz–1 MHz in the temperature range 20–350 °C. The room temperature polarization and dielectric permittivity of 250-nm-thick films were close to those in bulk ceramics. The films exhibited relaxor-type behavior with thermal hysteresis and with the temperatures of the dielectric peaks corresponding to those in the bulk. The width of the transition in the films was larger than in bulk ceramics. The properties of the films were found to be influenced by the small grain size rather than by the interfaces of the films.