Abstract Relaxor ferroelectrics play an important role for technological applications, mainly for using in the fabrication of actuators, transducers and sensors. Therefore, there has been an increasing interest of the scientific community in the investigation of the physical properties of such system in order to better elucidate the observed intriguing and unsolved phenomena. In this work, relaxor Pb(Mg1/3Nb2/3)O3 (PMN) ceramic system was prepared and the dielectric properties have been studied in details as a function of frequency, temperature and magnitude of the DC-bias electric field. Results reveal that the temperature dependence of the dielectric permittivity can be successfully described in the whole analyzed temperature range (100–400 K) by using a macroscopic statistical model, which describe the dielectric response in relaxor systems with diffuse phase transition (DPT). By using this phenomenological model, the temperature and DC-bias electric field dependences of the dielectric permittivity have been also revisited, from the analysis of the DPT behavior, promoting a careful discussion on the nature of the phase transition in relaxors materials. The calculated sizes of the polar nanoregions (PNRs) suggest the development of a structural disorder in the studied system, which promote the high diffuse ferroelectric transition as the amplitude of the DC-bias electric field increases.

Ferroelectric materials have been studied over the last three decades due to their exceptional physical properties, which make them promissory for several applications, such as pyroelectric sensors, nonvolatile memories, electro-optical devices, capacitors, etc. Among them, lead titanate (PbTiO3, PT), which has a tetragonal (P4mm) perovskite structure, has been considered a promising material for infrared detector applications (in both thin films and ceramic forms) and, therefore, it has been up today under the interest of many researches from the scientific community. In fact, recent advances in the synthesis methods for obtaining PT-based materials have promoted very interesting and intriguing phenomena in their micro(structural) properties, which still remains not fully understood. In this context, this work aims the investigation of the structural properties of PbTiO3 thin films, studied through X-ray diffraction and Raman spectroscopy techniques. In particular, the influence of the synthesis parameters, such as pyrolysis temperature, has been considered.

La-modified PbZrTiO3 ferroelectric ceramics with Pb0.92La0.08(Zr0.686Ti0.294)O3 nominal composition were obtained via the conventional solid-state reaction method, by considering different PbO excess (5, 10 and 15 mol %). The structural properties, were investigated from X-ray diffraction (XRD) and Raman Spectroscopy techniques, both at room temperature. Results confirmed the formation of the perovskite structure with rhombohedral symmetry (R3m space-group) for all the samples. The dielectric properties were also investigated, from the temperature dependence of the dielectric response, and results revealed the characteristic response of ferroelectric materials for all the compositions. The obtained very broad peak in the maximum dielectric permittivity, around Tm (~107°C), suggests the diffuse character of the ferroelectric-paraelectric phase transition.

PbTiO3 (PT) thin films were prepared by chemical route to study the effects of heat treatment on the phase transformations. Different pyrolysis temperatures between 250°C and 450°C have been studied to obtain films free of undesirable phases. The pyrolysis temperature directly affects the residual stresses and suppression of pyrochlore phases observed. The prediction of the preparation conditions is not straightforward. X-ray diffraction and Raman scattering results reflect a tetragonal structure obtained for the films. The results of X-ray diffraction for films produced above the pyrolysis temperature of 400°C showed a dominant orientation in the plane (111), which coexists with a small tendency along the plane (100). Raman spectroscopy with polarized light was used to evaluate the orientation effects of the ferroelectric domains present in the sample. The phase transformations in the films are discussed in terms of experimental calculations of residual stress.

The dynamic dielectric response of Pb(Mg1/3Nb2/3 )O3 ceramic was experimentally studied as a function of the EAC amplitude field. An increase in real dielectric permittivity was obtained by increasing the applied electrical field within the investigated temperature range for frequencies below 10 kHz. The temperature of maximum dielectric permittivity and freezing temperature decreased with an increase in E AC. Nonlinear permittivity was studied and found to behave similarly to freezing temperature. A statistical model was used to fit the dielectric dispersion of real dielectric permittivity with temperature and frequency. The results are discussed in terms of different factors’ contributions to dielectric permittivity under different EAC field conditions.

Electromechanical and dielectric properties of PMN–PT ferroelectric ceramics are investigated. In particular, dielectric response studies focus on the investigation of the influence of the DC applied electric field on the dielectric permittivity as a function of temperature and frequency. Results reveal an electric field driven dielectric anomaly in the dielectric permittivity curves, [Formula: see text], which in turn prevails in the whole ferroelectric phase region and continuously vanishes for temperatures near the paraelectric-ferroelectric phase transition temperature. A schematic model for the domains dynamics of the studied material is proposed taking into account the simultaneous contribution of both 90[Formula: see text] and 180[Formula: see text] domains walls.

The intrinsic contribution of dielectric permittivity was obtained in thin films of PZT pyrolyzed at different temperatures. Pyrochlore phases were observed in films pyrolyzed at temperatures above 350 degrees C, while only the perovskite phase grows in films pyrolyzed at temperatures lower than 300 degrees C. Dielectric and ferroelectric properties were characterized, and their behaviors were related to pyrolysis temperature. The dielectric permittivity dependence on the bias electric field was investigated at room temperature for different PZT thin films, and these curves were used to reconstruct the hysteresis loops. In this work, a model was used to reconstruct the hysteretic behavior of the films. The experimental results are in excellent agreement with the applied model.

Lead-free Bi0.506Na0.46Ba0.08-3x/2LaxTiO3 thin-films, with x = 0, 0.01, 0.02 and 0.03, have been synthesized via Sol-Gel process and the spin-coating technique. High quality thin-films have been obtained, revealing the formation of the perovskite structure with the minor Bi2Ti2O7 pyrochlore phase. A shift of the reflection in the 2 theta range of 31-34 degrees has been observed with the increase of the lanthanum dopant, suggesting the selective substitution of La3+ ions at the A-site of the BNT-BT perovskite structure.

The temperature dependences of the linear and nonlinear components of the dielectric permittivity of PMN ceramics were determined as a function of bias electric fields. The influence of the applied bias electrical field, superimposed to the small signal oscillating electrical field, is investigated. A decrease in the real dielectric permittivity with increasing the applied bias electrical field was obtained for the investigated temperature range. The temperature dependence of the nonlinear dielectric response reveals an anomalous behavior, indicating a phase transition induced by the bias electric field. The present investigation revealed the influence of the bias electric field on the freezing temperature and activation energy. The results were discussed according to a spherical random bond-random field glassy model for relaxors.

The compositional dependence of the piezoelectric properties of self-polarized PbZr1-xTixO3 (PZT) thin films deposited on Pt/TiO2/SiO2/Si substrates (x = 0.47, 0.49 and 0.50) was investigated by in situ synchrotron X-ray diffraction and electrical measurements. The latter evidenced an imprint effect in the studied PZT films, which is pronounced for films with the composition of x = 0.50 and tends to disappear for x = 0.47. These findings were confirmed by in situ X-ray diffraction along the crystalline [100] and [110] directions of the films with different compositions revealing asymmetric butterfly loops of the piezoelectric strain as a function of the electric field; the asymmetry is more pronounced for the PZT film with a composition of x = 0.50, thus indicating a higher built-in electric field. The enhancement of the dielectric permittivity and the effective piezoelectric coefficient at compositions around the morphotropic phase boundary were interpreted in terms of the polarization rotation mechanism and the monoclinic phase in the studied PZT thin films.

Piezoelectric properties of randomly oriented self-polarized PbZr0.50Ti0.50O3 (PZT) thin films were investigated using in situ synchrotron X-ray diffraction. Possibilities for investigating the piezoelectric effect using micro-sized hard X-ray beams are demonstrated and perspectives for future dynamical measurements on PZT samples with variety of compositions and thicknesses are given. Studies performed on the crystalline [100, 110] directions evidenced piezoelectric anisotropy. The piezoelectric coefficient d33 was calculated in terms of the lab reference frame (dperp) and found to be two times larger along the [100] direction than along the [110] direction. The absolute values for the dperp amount to 120 and 230pm/V being in good agreement with experimental and theoretical values found in literature for bulk PZT ceramics.

The effects of heat treatment on the phase transformations of lead zirconate titanate Pb(Zr0.50Ti0.50)O-3 (PZT) thin films were studied. The pyrolysis temperature directly affected the densification, residual stresses, and suppression of the pyrochlore phase observed in the studied films. The evolution of the crystalline phases and the residual stress were characterized by different temperatures of pyrolysis in PZT thin films, using the X-ray diffraction technique. The phase transformations in the films are discussed in terms of theoretical and experimental calculations of residual stress.

Piezoeresponse force microscopy (PFM) and local piezoresponse hysteresis loops were used to study the imprint effect in PbZr1-xTixO3 thin films at compositions around the morphotropic phase boundary (MPB). Schottky barriers and mechanical coupling between film-substrate were excluded as origin for the imprint in these films. Comparing the composition dependence of the effective d(33) before poling with some reports in the literature, the existence of point defects such as complex vacancies (and Ti3+ centers is discussed as probable origin for the imprint effect observed here.

The effects of heat-treatment conditions on crystallographic orientation and phase transformations were studied on lead zirconate titanate Pb(Zr0.50Ti0.50)O3 (PZT) thin films. Films deposited on platinum with a chemical solution can exhibit 111 or 100 texture, however, there is no consensus about the mechanisms responsible for texture during heat treatment processes. The heat treatment affects directly the densification of the film as well as the residual stress developed. In addition, the formation of impurities as a pyrochlore phase (Pb2(Zr1-xTix)2O6) was noticed by several authors. In this work, the evolution of phases and trends of texture were characterized for different temperatures of pyrolysis in PZT thin films using X-ray diffraction. The perovskite phase coexists with the pyLicearochlore phase to the film pyrolyzed from 350 °C to 450 °C. However, the films produced at low temperature pyrolysis showed only the presence of the perovskite phase. The Rietveld method was used to quantify the percentage of each phase as a function of temperature of pyrolysis. The microstrain and the residual stress was evaluated to explain the mechanisms responsible for texture and phase transformations in PZT films.

PbZr1−xTixO3 (PZT) thin films (x = 0.46, 0.47, 0.48, 0.49, and 0.50) were deposited on Pt/TiO2/SiO2/Si substrates using a polymeric chemical method to study the effects of the composition on the macroscopic electrical and local piezoelectric properties. Both measurements demonstrate the existence of a self-polarization effect in all studied PZT films. The measurements were discussed in terms of the contribution of the Schottky barriers to the self-polarization effect. It is shown that both Schottky barrier effect and mechanical coupling near the film-substrate interface are not the dominant mechanisms responsible for the observed phenomena.

Physical properties of self-polarized PbZr1-xTixO3thin films with no preferential orientation were reported at 0.46 x 0.50 compositions. Structural analysis reveals coexistence between monoclinic-tetragonal and monoclinic-rhombohedral phases at 0.46 x 0.49, where the monoclinic phase is in majority over both tetragonal and rhombohedral phases. The dielectric permittivity (ε ́ = 447) shows a maximum at around x = 0.48. Asymmetries on macroscopic and local hysteresis loops confirm the self-polarization effect in the studied films.

Lead zirconate titanate Pb(Zr0.50Ti0.50)O3 (PZT) thin films were deposited by a polymeric chemical method on Pt(111)/Ti/SiO2/Si substrates to understand the mechanisms of phase transformations and the effect of film thickness on the structure, dielectric and piezoelectric properties in these films. PZT films pyrolyzed at temperatures higher than 350°C present a coexistence of pyrochlore and perovskite phases, while only perovskite phase grows in films pyrolyzed at temperatures lower than 300°C. For pyrochlore-free PZT thin films, a small (100) orientation tendency near the film-substrate interface was observed. Finally, we demonstrate the existence of a self-polarization effect in the studied PZT thin films. Results suggest that Schottky barriers and/or mechanical coupling near the film substrate interface are not primarily responsible for the observed self-polarization effect in our films.

This work demonstrates the existence of a self-polarization effect in Pb(Zr0.50Ti0.50)O3 thin films with no preferential orientation. Piezoresponse Force Microscopy (PFM) and dielectric measurements were used to study the origin of this effect. The presence of only one peak shifting slightly to the negative side in the piezoresponse histogram indicates the existence of a self-polarization effect in the studied films. An increase in self-polarization was observed when the film thickness increases from 200 nm to 710 nm. The results suggest that Schottky barriers and/or mechanical coupling near the film–electrode interface are not the main mechanisms responsible for the self-polarization effect in the studied films.

The structural properties of Pb(Zr0.50Ti0.50)O-3 thin films with no preferential orientation were studied throughout the film thickness. An analysis on depth profile shows the existence of a significant (1 0 0) alignment near the film-electrode interface. Nanoscale piezoelectric measurements demonstrate the existence of a self-polarization effect in the studied films. An increase in this effect with film thickness increasing from 200 to 710 nm suggests that Schottky barriers and/or mechanical coupling near the film-electrode interface cannot be the main mechanisms responsible for the self-polarization effect in the studied films.

The dielectric properties of the 0.65[Pb(Mg 1/3 Nb 2/3 )O 3 ]-0.35PbTiO 3 ferroelectric ceramic composition were investigated viewing the capability to be used for tunable microwave applications. The dielectric response has been studied for three selected temperatures (300 K, 370 K and 400 K), below the paraelectric-ferroelectric phase transition temperature, as a function of the applied `bias' electric field. The obtained dielectric tunability was found to be around 60%, under an electric field of 19 kV/cm, which makes the studied ceramic composition an excellent candidate for application in the electro-electronic industry, as tunable devices.