PbTiO3 Concentration Research Articles

Unusual crystal structure evolution, multiple phase boundaries and phase coexistence in (1 - x)Ba(Cu1/3Nb2/3)O3-(x)PbTiO3 perovskite solid solution.

Exploring the functionalities of materials requires a profound understanding of the crystal structure. In this paper, room temperature crystal structures of a new solid solution (1 - x)Ba(Cu1/3Nb2/3)O3-(x)PbTiO3 have been investigated in the entire compositional span and different crystallographic phases and phase coexistence regions have been discovered. The confirmation of the symmetry of these crystal structures has been done with the help of Rietveld analysis of the high-resolution XRD data. Despite both the end components, Ba(Cu1/3Nb2/3)O3 and PbTiO3, having tetragonal (P4mm) symmetry, new cubic and monoclinic phases have been discovered for the intermediate compositions with multiple phase boundaries. The composition region 0.05 ≤ x ≤ 0.55 exhibits a cubic crystal structure and increasing PbTiO3 concentration to 0.62 results in a unique coexistence of two tetragonal phases with different tetragonalities. This transformation is mediated by coexisting cubic and tetragonal phases, for 0.59 and 0.60. The crystal structure of the solid solution later transforms into coexisting monoclinic and tetragonal phases for a wider compositional span i.e., 0.65 ≤ x ≤ 0.85. This composition region is very fascinating, as two phenomenologically different monoclinic structures have been observed in it. Finally, a tetragonal phase at x = 1 is achieved through the mediation of two coexisting tetragonal phases, for the region 0.85 < x ≤ 0.975. The evolution of different crystallographic structures and the coexisting phases are critically comprehended using the variations in the lattice parameters and unit cell volume. The presence of multiple phase boundaries spread across a wide range of compositions makes this solid solution very intriguing and a viable choice for exploring different properties with compositional tuning.

Electrodynamic properties of solid solutions 0.98(xPbTiO3–yPbZrO3–zPbNb2/3Mg1/3O3)–0.02PbGeO3 in the microwave range

The behavior of samples of four-component solid solutions (SS) 0.98(xPbTiO3–yPbZrO3–zPbNb2/3Mg1/3O3)–0.02PbGeO3 in an electromagnetic field of the microwave range has been studied by the microstrip method. Dependences of frequency dispersion of the transmission coefficient, the reflection coefficient, and the degree of absorption of the material on PbTiO3 concentration have been analyzed. It has been found that the flat disk samples with the highest PbTiO3 concentration in the segment of the regular microstrip line have the widest absorption band (10 MHz ÷ 2.5 GHz).

Photoluminescence in Er-doped 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3 solid solutions

Photoluminescence and optical second harmonic generation in Er-doped 0.4Na0.5Bi0.5TiO3-(0.6-x)SrTiO3-xPbTiO3 solid solutions is studied. Earlier, it was shown that upon increasing of PbTiO3 concentration transfer from relaxor to ferroelectric state takes place in these compositions. Here, role of PbTiO3 and Er concentration on stability of the ferroelectric state is evaluated, taking into account that luminescence, contrary to X-ray diffraction patterns and second harmonic intensity, is sensitive just to local environment around Er3+ ions. Luminescence spectra at low temperatures are measured in order to detect variations of local environment in comparison with Er-doped Na0.5Bi0.5TiO3.

Effect of PbTiO3 concentration on structural, paramagnetic resonance and magnetoelectric properties of PbTiO3:SrFe12O19 multiferroic nanocomposites

Polycrystalline multiferroic nanocomposites of compositions (x) PbTiO3 – (1-x) SrFe12O19 where x = 0.10, 0.20, 0.30 and 0.50 are prepared by the solid state solution method and characterized their structural, magnetic and magnetoelectric properties to establish correlation among them for use in chemical sensors application. XRD patterns exhibit the broadening of diffraction peaks with PbTiO3 concentration due to the distortion induced by Pb2+ and Ti4+ ions doping in SrFe12O19 lattice. The asymmetrical peak broadening and peak positions shift in Raman spectra arise from phonon confinements and compressive stress developed in SrFe12O19 lattice by the addition of PbTiO3. The role of PbTiO3 concentration on spins dynamics and magnetic interactions in these multiferroic nanocomposites has been inferred from Electron Paramagnetic Resonance (EPR) parameters. EPR spectra depict the ferromagnetic nature of nanocomposites and higher g-values as compared to free electron g – value showed the strong magnetic interactions among grains. The decrease in peak-to-peak line width, g-value, spin concentration and spin-spin relaxation time constant for x = 0.10, 0.20, 0.50 concentrations of PbTiO3 in nanocomposites reveals the decrease in magnetic interactions. While for x = 0.30 analogue, the exceptional increase in all the parameters is due to grain growth in the form of rod like structures. Magnetoelectric coupling coefficient (αME) values exhibit maximum value 0.51 for x = 0.30 composition owing to magnetostriction and the increase in grain size for x = 0.30 as compared to other composition.

Двухфазность кристаллической структуры твердых растворов (1-x)PbFe-=SUB=-2/3-=/SUB=-W-=SUB=-1/3-=/SUB=-O-=SUB=-3-=/SUB=--xPbTiO-=SUB=-3-=/SUB=- (x=0.25,0.3,0.35) при комнатной температуре

The evolution of the crystal structure of (1-x) PbFe2 / 3W1 / 3O3 - хPbTiO3 solid solutions depending on the PbTiO3concentrations (at x = 0.25, 0.3, 0.35) in the region of the morphotropic phase boundary was studied using x-ray diffraction at room temperature. It was established that all three compositions are a mixture of cubic and tetragonal phases, and an increase in the concentration of PbTiO3 above 30 mol. % leads to an increase of the tetragonal phase contribution. The parameters of the crystal structure and the content of both phases in these solid solutions are determined. It was shown that at room temperature there are static displacements of lead ions from the principle crystallographic positions.

Dielectric and Thermal Properties of Tetragonal PbTiO3 Nanoparticles/Clusters Embedded in Lithium Tetraborate Glass Matrix

PbTiO3 nanoparticles/clusters embedded in lithium tetraborate glass matrix (glass nanocomposite (GNCs)) of composition (100-x) Li2B4O7-xPbTiO3 (where x = 5, 10, 15 and 20 in mol %) were synthesized. The presence of glassy phase in all GNCs samples was identified by X-ray diffraction (XRD) and differential scanning calorimetric (DSC) studies. The structure of PbTiO3 used in the preparation of these samples is a ferroelectric tetragonal phase (space group P4mm) which is confirmed by Rietveld refinement of XRD data. Transmission electron microscopic (TEM) images exhibit PbTiO3 nanoparticles/clusters phase embedded in lithium tetraborate glass matrix. The ferroelectric to paraelectric phase transition of PbTiO3 nanoparticles/clusters in the GNCs samples was established from DSC and dielectric studies. The thermal, density, dielectric and Ac conductivity behavior of the GNCs samples depends on the change in the coordination number of the network former and the concentration of PbTiO3 in the glass matrix.

Improved crystallization of perovskite films using PbTiO3-decorated mesoporous scaffold layers for high stable carbon-counter-electrode solar cells

Abstract The quality of perovskite film has great influence on photovoltaic performance of mesoscopic organic-inorganic halide perovskite solar cells, which is related to the mesoporous scaffold layers. In this paper, we present a modified two-step method to fabricate PbTiO3-decorated mesoporous scaffold layers for growing high-quality perovskite film, in which the mesoporous layers are treated by different concentration of Pb2+ solution. The introduction of moderate concentration of PbTiO3 is seen to promote the perovskite film growing and crystallizing, leading to reducing carrier recombination loss and defect density. The perovskite film based on treating concentration of 0.05 M exhibits larger size of crystal blocks, better quality of films, and higher surface coverage. Such a film applies in hole-counter-free perovskite solar cells with carbon-counter-electrode to obtain a power conversion efficiency of 10.55% along with a high open circuit voltage of 1.00 V. Moreover, these devices exhibit excellent long-term stability in an ambient atmosphere, which is related to the presence of the carbon electrode and PbTiO3.

EMI shielding properties of laminated graphene and PbTiO3 reinforced poly(3,4-ethylenedioxythiophene) nanocomposites

In this paper, PEDOT/reduced graphene oxide (RGO)/PbTiO3 nanocomposites have been synthesized using facile insitu chemical oxidative polymerization method. The synthesis method leads to the formation of core-shell structured nanocomposites containing PbTiO3 as primary filler and RGO as secondary filler in PEDOT matrix. The core-shell morphology of the composites has been confirmed using transmission electron microscope with average particle size 20–30 nm observed for PbTiO3. The incorporation of RGO and PbTiO3 in the PEDOT matrix has been confirmed by X-ray diffraction. A systematic study on electromagnetic shielding properties and the effect of PbTiO3 concentration on different properties has been carried out. The ferro-electric PbTiO3 with RGO induced dielectric loss in the composites, whereas, PEDOT establish a conducting network over RGO layer and PbTiO3 nanoparticles that improve electromagnetic shielding properties by increasing the dielectric loss. As a result, an enhanced electromagnetic shielding effectiveness value of 51.94 dB (>99.999% attenuation) has been achieved in 12.4–18 GHz frequency range. The nanocomposites were further characterized using Fourier transmission infrared spectroscopy and thermal gravimetric analysis.

Strain-induced nanostructure of Pb(Mg1/3Nb2/3)O3–PbTiO3 on SrTiO3 epitaxial thin films with low PbTiO3 concentration

The singularity of the structure in (1 − x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–xPT) (x = 0–50 mol %) epitaxial thin films of 100 nm thickness was investigated from the viewpoint of the localized residual strain in the nanoscale. The films were deposited on SrTiO3 (STO) (001) single-crystal substrates by chemical solution deposition (CSD) using metallo-organic decomposition (MOD) solutions. X-ray and electron diffraction patterns revealed that PMN–xPT thin films included a single phase of the perovskite-type structure with the cube-on-cube orientation relationship between PMN–xPT and STO: (001)Film ∥ (001)Sub, [100]Film ∥ [100]Sub. X-ray reciprocal space maps showed an in-plane tensile strain in all the compositional ranges considered. Unit cells in the films were strained from the rhombohedral (pseudocubic) (R) phase to a lower symmetry crystal system, the monoclinic (MB) phase. The morphotropic phase boundary (MPB) that split the R and tetragonal (T) phases was observed at x = 30–35 for bulk crystals of PMN–xPT, whereas the strain suppressed the transformation from the R phase to the T phase in the films up to x = 50. High-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) analysis and its related local strain analysis revealed that all of the films have a bilayer morphology. The nanoscale strained layer formed only above the film/substrate semi-coherent interface. The misfit dislocations generated the localized and periodic strain fields deformed the unit cells between the dislocation cores from the R to an another type of the monoclinic (MA) phase. Thus, the singular and localized residual strains in the PMN–xPT/STO (001) epitaxial thin films affect the phase stability around the MPB composition and result in the MPB shift phenomena.

An analysis of the high-temperature phase structure of multiferroic solid solutions of the PFW–PT

The temperature evolution of multiferroic solid solutions of the PFW–PT system, namely a (1–x)Pb(Fe2/3W1/3O3)–(x)PbTiO3 crystal structure where x = 0, 0.2, 0.3, has been studied by neutron powder diffraction in the region of the morphotropic phase boundary. The coexistence of cubic and tetragonal phases in the solutions with x = 0.2, 0.3 was found below T = 259 and 285K, respectively. As a result of the data treatment, the atom coordinates, the occupation factors and the temperature dependences of cell parameters were determined in the cubic perovskite phase. The refinement of the crystal structure in terms of ideal perovskite exhibited anomalously large Debye–Waller factors for the lead cations, indicating the appearance of random static displacements of these cations from the ideal perovskite (000) position. Using the split-ion model we estimated the value of Pb static shifts (∼0.1Å) from their high-symmetry positions along the [110] direction. It was shown that these shifts decrease with increasing the PbTiO3 concentration.

Phase transitions in Na0.5Bi0.5TiO3-(Sr0.7Bi0.2)TiO3-PbTiO3 solid solutions

ABSTRACTIncreasing of Sr0.7Bi0.2TiO3 concentration in Na0.5Bi0.5TiO3-Sr0.7Bi0.2TiO3 solid solutions causes increasing of Bi/Na relation and vacancies in the A-site of perovskite structure. In temperature dependence of dielectric permittivity, such a change of composition is reflected by transforming of the frequency-dependent shoulder into a maximum characteristic for relaxor ferroelectrics and diminishing of the frequency-independent maximum characteristic for Na0.5Bi0.5TiO3. Here changes in behavior of dielectric permittivity and polarization are studied if PbTiO3 is added in a certain concentration range of Na0.5Bi0.5TiO3-Sr0.7Bi0.2TiO3 solid solutions. Changes of the characteristic temperatures as a function of PbTiO3 concentration are determined. Behavior of the electrocaloric effect is compared with the results obtained for Na0.5Bi0.5TiO3-SrTiO3-PbTiO3.

Kinetics of the phase transition in crystals PbIn1/2Nb1/2O3–PbMg1/3Nb2/3O3–x PbTiO3

The time dependences of the optical transmission, velocity of sound, and elastic constants at room temperature in a number of the [001]-oriented PbIn1/2Nb1/2O3–PbMg1/3Nb2/3O3–xPbTiO3 single crystals with the compositions lying both far from the morphotropic phase boundary and in its vicinity have been investigated. The analysis of the data obtained has been carried out. It has been shown that, in all the studied crystals, phase transitions induced by an electric field occur in two stages: the first stage is an incubation period associated with a small increase in the polarization of a part of the sample being in the glass phase, and the second phase (after the incubation period τ) is a rapid increase in the polarization and the formation of a long-range order. It has been found that the time τ depends on how close is the temperature of measurements to the Vogel–Fulcher temperature Tf. The closer is the temperature of measurements to the Vogel–Fulcher temperature Tf, the weaker is the electric field required to be applied to the sample in order to induce a ferroelectric phase. It has been demonstrated that the phase state of the studied crystals is unstable, which manifests itself in a strong dependence of the incubation period τ on the time between the annealing of the sample and the beginning of the measurements. The stability of the phase state depends on the PbTiO3 concentration: an increase in the concentration leads to a significant increase in the stability.

Study of Tetragonal Phase in 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3 Solid Solutions by Second-Harmonic Generation

Description of the local symmetry of relaxor ferroelectrics, especially in connection with nature of polar nanoregions, is one of the key questions in research of relaxor ferroelectrics. Unlike such well-known relaxor ferroelectrics as PbMg1/3Nb2/3O3 and (Pb,La)(Zr0.65Ti0.35)O3, ternary solid solutions 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3 show clear coexistence of phases of tetragonal and cubic symmetry, which is established by x-ray diffractometry. Since the second-harmonic generation spectroscopy is a sensitive tool in determination of deviation from symmetry, containing a centre of inversion, it is used as an additional method in characterization of structure in 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3. Measurements indicate low, increasing intensity of the second-harmonic generation upon decreasing of temperature, for the samples with low concentration of PbTiO3. Whereas an abrupt change is observed at the phase transition between ferroelectric and relaxor states for the samples with higher concentrations of PbTiO3.

Variation of Piezoelectric properties and mechanisms across the relaxor-like/Ferroelectric continuum in BiFeO3- (K0.5Bi0.5)TiO3-PbTiO3 ceramics.

1- x - y)BiFeO3-x(K0.5Bi0.5)TiO3-yPbTiO3 (BFKBT- PT) piezoelectric ceramics were investigated across the compositional space and contrasted against the xBiFeO3- (1-x)(K0.5Bi0.5)TiO3 (BF-KBT) system, whereby a range of relaxor-like/ferroelectric behavior was observed. Structural and piezoelectric properties were closely related to the PbTiO3 concentration; below a critical concentration, relaxor-like behavior was identified. The mechanisms governing the piezoelectric behavior were investigated with structural, electrical, and imaging techniques. X-ray diffraction established that longrange non-centrosymmetric crystallographic order was evident above a critical PbTiO3 concentration, y > 0.1125. Commensurate with the structural analysis, electric-field-induced strain responses showed electrostrictive behavior in the PbTiO3-reduced compositions, with increased piezoelectric switching in PbTiO3-rich compositions. Positive-up-negative-down (PUND) analysis was used to confirm electric-field-induced polarization measurements, elucidating that the addition of PbTiO3 increased the switchable polarization and ferroelectric ordering. Piezoresponse force microscopy (PFM) of the BF-KBT-PT system exhibited typical domain patterns above a critical PbTiO3 threshold, with no ferroelectric domains observed in the BF-KBT system in the pseudocubic region. Doping of BiFeO3-PbTiO3 has been unsuccessful in the search for hightemperature materials that offer satisfactory piezoelectric properties; however, this system demonstrates that the partial substitution of alternative end-members can be an effective method. The partial substitution of PbTiO3 into BF-KBT enables long-range non-centrosymmetric crystallographic order, resulting in increased polar order and TC, compared with the pseudocubic region. The search for novel high-temperature piezoelectric ceramics can therefore exploit the accommodating nature of the perovskite family, which allows significant variance in chemical and physical characters in the exploration of new solid-solutions.

An effective growth method to improve the homogeneity of relaxor ferroelectric single crystal Pb(In1/2Nb1/2)O3‐ Pb(Mg1/3Nb2/3)O3‐PbTiO3

Compositional segregation usually has negative effects on the growth of solid solution ferroelectric single crystals of Pb(In1/2Nb1/2)O3‐Pb(Mg1/3Nb2/3)O3‐PbTiO3 (abbr. PIN‐PMN‐PT or PIMNT). A modified Bridgman method was adopted in this work to control the segregation and improve the compositional homogeneity significantly. The characteristic of this work is to use multiround growths and gradient composition raw materials in order to keep the PbTiO3 concentration constant during the crystal growth. As an example, the two‐round growth of ternary PIN‐PMN‐PT single crystal is conducted in the same Pt crucible with gradient raw materials, where the first‐round boule was used as the seed crystal for the second‐round growth. Our results show that the as‐grown (Ф80 mm × 270 mm) PIN‐PMN‐PT crystals exhibit higher phase transition temperatures (Tc∼180 °C, Tr/t∼110 °C) and larger coercive field (Ec∼5–5.5 kV/cm), which are much better than the performances of Pb(Mg1/3Nb2/3)O3‐PbTiO3 crystals, and similar dielectric and piezoelectric performances (ε∼5000, tanδ∼1.25%, d33∼1500 pC/N, kt∼60%). And about 85 percent of the crystal boule grown by the two‐round growth technique could maintain its compositions around the morphotropic phase boundary.

Stabilization of metastable tetragonal phase in a rhombohedral magnetoelectric multiferroic BiFeO3–PbTiO3

The phase formation behaviour of the magnetoelectric multiferroic 0.8BiFeO3–0.2PbTiO3 was studied as a function of heat treatment at different temperatures of a sol–gel derived powder. While under ordinary synthesis conditions this composition exhibits antiferromagnetic ordering and a rhombohedral structure; the sol–gel-enabled low-temperature synthesis could stabilize a tetragonal metastable phase along with the stable rhombohedral phase, mimicking a morphotropic phase boundary state. The phase coexistence state exhibits relatively enhanced ferromagnetic correlation. The same system with a relatively higher PbTiO3 concentration, 0.65BiFeO3–0.35PbTiO3, on the other hand, exhibits a rhombohedral metastable phase. These results suggest that the occurrence of metastable phases is a very common feature in the BiFeO3–PbTiO3 magnetoelectric ferroelectric system and that it affects the ferroelectric and magnetic properties of system quite remarkably.

Electrocaloric properties in relaxor ferroelectric (1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 system

The electrocaloric effect (ECE) in the Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) solid solution system was investigated by means of detailed direct temperature measurements as a function of temperature, composition, and electric field. The (1−x)PMN-xPT ceramics of compositions 0 ≤ x ≤ 0.3 were fabricated by the columbite route. In opposite to conventional ferroelectrics, the maximum of electrocaloric effect was found to shift from the proximity of depolarization/Curie temperature to higher temperatures above a certain composition-dependent electric field strengths. Especially, the compositions with low PT content showed a broadened temperature range of electrocaloric effect. With increasing PbTiO3 concentration, the magnitude of ΔT increased, and the temperature dependence of the maximum ECE response gradually developed towards a more pronounced anomaly typical for conventional ferroelectrics. The arising high temperature electrocaloric effect in the ergodic relaxor phase was attributed to the contribution from polar nanoregions. All the compositions studied showed the highest electrocaloric activity just above the depolarization/Curie temperature close to the possible critical point, as recently predicted and observed for some compositions. The magnitude of the maximum electrocaloric temperature change was in the range of ΔT = 0.77–1.55 °C under an electric field strength of 50 kV/cm.

Tailoring the structure and piezoelectric properties of BiFeO3-(K0.5Bi0.5)TiO3–PbTiO3 ceramics for high temperature applications

There is a growing requirement for piezoelectric materials and systems which can operate in extreme environments, for example, oil &amp; gas, and aerospace. Here, we present the high temperature BiFeO3-K0.5Bi0.5TiO3-PbTiO3 (BF-KBT-PT) polycrystalline perovskite system. X-ray diffraction, impedance analysis, and Berlincourt measurements reveal a large region of phase coexistence, which can be tailored to optimise performance; Tc and the tetragonal spontaneous strain correlate strongly with the PbTiO3 concentration. The highest temperature composition has a d33 of 140 pmV−1 with a Tc = 542 °C, occupying previously unchartered territory on the classical d33–TC plot.

Synthesis, structure and dielectric properties of (1−x)[0.9BiFeO3–0.1DyFeO3]–xPbTiO3 pseudo-binary ceramics

In order to develop multiferroics with large magnetization and polarization, we have prepared a series of (1−x)[0.9BiFeO3–0.1DyFeO3]–xPbTiO3 [BDF–xPT] solid solution ceramics by solid state reaction. X-ray diffraction reveals that, with the increase of PbTiO3 concentration, the solid solution transforms from a rhombohedral to a tetragonal phase with the presence of a morphotropic phase boundary (MPB) region located at 0.28≤x≤0.40 at room temperature, in which the rhombohedral, tetragonal and orthorhombic phases coexist. The temperature dependence of the dielectric permittivity indicates that the Curie temperature decreases with the increasing amount of PbTiO3. Based upon the structural analysis and dielectric characterization, a preliminary phase diagram for the BDF−xPT pseudo-binary system has been proposed. It is found that the ceramics of compositions around the MPB exhibits much better dielectric properties with dielectric constant of the BDF–0.37PT ceramics reaching 459 at 1kHz, confirming the beneficial effects of the MPB on the dielectric performance.

Effects of temperature and concentration of La in the form of A1 transverse optical phonon in the PbTiO3 system

The structural phase transition from ferroelectric to paraelectric was studied by Raman scattering in the ceramic lead titanate (PbTiO3) doped with lanthanum (La). A1 vibrational mode contains some sub-peaks that have been associated in literature with PbTiO3 concentration (Ca, Ba), and effects of high temperatures as it approaches the Curie temperature (Tc). Raman new study shows that the anomalous behavior of the A1 mode is not only caused by the effects of concentration or temperature near Tc, but by anharmonicity and defects in the network in the PbTiO3 thermodynamically are inevitable. This effect was studied by a wide temperature range from 10 K to Tc in each sample (La = 0, 5, 10, 15, 20%), showing that the effect depends not only on the high temperatures in the pure PT.