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In this paper, we studied some ferroelectric properties of archetypal oxide uniaxial ferroelectric single crystals of Pb

The origin of the strong piezoelectric phenomenon in PbZr1−xTixO3 (PZT) perovskites still suffers from a lack of complete understanding. It concerns the distinction between the intrinsic and extrinsic mechanisms that govern PZT's piezo activity. These two mechanisms have been investigated in single crystal PbZr0.54Ti0.46O3 at the morphotropic phase boundary. After poling in a DC electric field, the piezoelectric properties were examined on the same crystal by observing piezoelectric resonances to determine the piezoelectric coefficient d31 and measuring quasistatic deformation to determine the coefficient d33. The domain populations were investigated during and after poling in a DC electric field. These populations were also investigated as a function of DC fields for strengths similar to those used to measure quasistatic piezoelectric properties for a poled crystal. The experiments indicate that the intrinsic origin of the enhancement of the piezoelectric properties is connected with a change in the population of domains with monoclinic symmetry, in which there is an easy polarization rotation under the action of the electric field.

Struvite (MgNH4PO4·6H2O) is a mineral first identified in 1845. It is tested for several reasons: (1) it is a problem in liquid wastewater treatment plants; (2) on the other hand, it is recovered from this wastewater because of phosphorus, magnesium, and nitrogen; (3) it is the main component of infectious urinary stones. In this paper, we present the first experimental evidences of the ferroelectric nature of struvite at room temperature. Struvite shows a hysteresis loop and spontaneous electric polarization that can be reversed by an application of an external electric field. The measured value of residual polarization of struvite is equal to 0.95 μC/cm2. We also report observations of the ferroelectric domains in struvite using birefringence imaging technique. The non-centrosymmetry of the crystal lattice is confirmed with the use of the Kurtz−Perry powder test. The second harmonic generation response for struvite in relation to that of potassium dihydrogen phosphate is 0.36. We suggest that ferroelectric properties for struvite, in particular, spontaneous polarization, can have a significant impact on the behavior of struvite in aqueous solutions, such as liquid wastewater or urine.

In this paper, we present the first experimental evidence of the piezoelectric nature of struvite (MgNH4PO4·6H2O). Using a single diffusion gel growth technique, we have grown struvite crystals in the form of plane parallel plates. For struvite crystals of this shape, we measured the piezoelectric coefficients d33 and d32. We have found that at room temperature the value of piezoelectric coefficient d33 is 3.5 pm/V, while that of d32 is 4.7 pm/V. These values are comparable with the values for other minerals. Struvite shows stable piezoelectric properties up to the temperature slightly above 350 K, for the heating rate of 0.4 K/min. For this heating rate, and above this temperature, the thermal decomposition of struvite begins, which, consequently, leads to its transformation into dittmarite with the same non-centrosymmetric symmetry as in case of struvite. The struvite-dittmarite transformation temperature is dependent on the heating rate. The higher the heating rate, the higher the temperature of this transformation. We have also shown that dittmarite, like struvite exhibits piezoelectric properties.

This report documents the electrical features of (1-x) Pb(Zr0·70Ti0.30)O3–x BiMn2O5 ceramics with x = 0–0.05 (PZT–BM). A structural disorder was introduced by doping with non-polar bismuth manganite (BM) to increase the chemical disorder in PZT ceramics, which is one of the reasons for its marked piezoelectric properties. The chemical disorder was confirmed using scanning electron microscopy. The rhombohedral symmetry of a crystal lattice was determined using the XRD powder test. To assess the influence of BM dopant on the electric properties of PZT, dielectric spectroscopy was performed at a frequency f = 1 kHz–1 MHz and in a temperature range of 290–680 K. Several effects on the dielectric characteristics were induced by the addition of BM, including the shift and diffuseness of the transition from the ferroelectric to the paraelectric phase and the diffuseness of the transition between two ferroelectric phases. The electrical conductivity increased as the BM content increased. Piezoelectric studies have shown that 0.99 PZT–0.01 BM ceramics exhibit better piezoelectric properties and higher permittivity than pure PZT ceramics. The 0.99 PZT–0.01 BM piezoelectric coefficient d33 increased by approximately 30% compared with pure PZT.

Lead zirconate-titanate PbZr0.70Ti0.30O3 ceramics doped with bismuth oxide has been investigated. Dielectric and optical measurements were performed to check the dopant influence on phase transitions and pre-transitional effects. It has been postulated that the temperature at which maximum permittivity occurs is not connected with structural phase transitions.

An expansive library of structurally complex two-dimensional (2D) and three-dimensional (3D) lead halide perov-skites has emerged over the past decade, finding applications in various aspects of photon management: photovoltaics, photo-detection, light emission, and nonlinear optics. Needless to say, the highest degree of structural plasticity enjoys the former group, offering a rich playground for modifications of relevant optoelec-tronic parameters such as exciton energy. Structural tailorability is reflected in the ease of modification of the chemistry of the organic layers residing between inorganic slabs. In this vein, we show that the introduction of methylhydrazinium cation (MHy+, CH3NH2NH2+) into 2D perovskite gives a material with a record low separation of the inorganic layers (8.91 Å at 300 K). Optical studies showed that MHy2PbBr4 features the most red-shifted excitonic absorption among all known A2PbBr4 compounds as well as a small exciton binding energy of 99.9 meV. MHy2PbBr4 crystallizes in polar Pmn21 symmetry at room emperature (phase III) and at 351 K undergoes a phase transition to modulated Pmnm phase (II) followed by another phase transition at 371 K to Pmnm phase (I). The ferroelectric property of room-temperature phase III is inferred from switching of the pyrocurrent, dielectric measurements, and optical birefringence results. MHy2PbBr4 exhibits multiple nonlinear optical phenomena such as second-harmonic generation, third-harmonic generation, two-photon excited luminescence, and multiphoton excited luminescence. Analysis of MHy2PbBr4 single-crystal luminescence spectra obtained through linear and nonlinear optical excitation pathways indicates that free exciton emission is readily probed by the ultraviolet excitation, whereas crumpled exciton emission is detected under two- and multiphoton excitation conditions. Overall, our results demonstrate that incorporation of MHy+ into the organic layer is an emergent strategy for obtaining a 2D perovskite with polar character and multifunctional properties.

PbZr1-xTixO3 perovskite materials, known as PZT, are highly applicable, mainly due to their extraordinary piezoelectric properties. Recently, a technology of PZT crystals growth has been elaborated and opened new investigation possibilities for these compounds. In this paper, we demonstrate a highly piezoelectric response in PbZr0.87Ti0.13O3 single crystal. Under the action of an electric field, the piezoelectric coefficient d33 turns out to be over 2500 pm V-1. The optical studies performed have proved a significant influence of the domain dynamics on such high-efficiency piezoelectric response. Monoclinic M and rhombohedral R phases have been observed in the lead zirconate-titanate crystals with a low Ti content. This coexistence of phases with different symmetries and dense domain walls are the primary sources of high piezoelectric response. We have observed that strong electric fields may act on randomly oriented polarization vectors so that the total piezoelectric activity disappears, and the unusual isotropization point near 250 °C appears.

We have succeeded to grow single PbZr1-xTixO3 (PZT) crystal with Ti content of the order of x = 0.13. PZT compound with such Ti concentration is characterised by structural coexistence of the rhombohedral and monoclinic structures at each temperature below TC. It seems that investigations of the dielectric, piezoelectric and optical properties confirm this highly complicated co-existence.

Frequency and temperature dielectric response and electrical conductivity behavior around the antiferroelectric–paraelectric phase transition temperature were studied in PbZr0.93Sn0.07O3 antiferroelectric single crystals. The contribution of conductive processes to dielectric relaxation for the studied frequency range is discussed, considering oxygen vacancies and electronic transport. The relaxation processes below the transition temperature are associated with short-range polaronic hopping due to the interaction of the charge carriers (trapped electrons) with the distorted crystal lattice. Based on the specific coupling between electrons and phonons in the largely distorted oxygen octahedral sublattice of PbZr1−xSnxO3 crystals, an attempt to explain the formation of the incommensurate phase was undertaken.

The temperature and electric field dependences of electrocaloric effect (ECE) of Pb5Ge3O11 (PGO) single crystals, pure and doped with 0.2% of Cr3+ ions, were investigated by the indirect method using the Maxwell relationship. Based on a Maxwell relation, the ECE was characterized via P–T curves under different electric fields. Abnormal ECE with a negative temperature change (ΔT ~ −0.3 K) opposite to that of the normal ferroelectrics was found in the temperature range 390–400 K, several degrees before the phase transition. Normal positive ECE was found around the phase transition point and is of the order of 1.2 for pure PGO and 1.5 for the PGO crystals doped with Cr ions. The abnormal character of ECE originates from electronic conductivity which was detected in the plane perpendicular to the ferroelectric axis. The doping with Cr ion enhances the positive ECE and reduces the negative ECE.

Acoustic properties of antiferroelectric (AFE) PbZr0.72Sn0.28O3 single crystals were investigated in a wide temperature range by Brillouin light scattering spectroscopy. The Brillouin frequency shift of the longitudinal acoustic (LA) mode exhibited three abrupt changes corresponding to the successive phase transitions between the paraelectric, intermediate, antiferroelectric (AFE2) and antiferroelectric (AFE1) phases upon cooling. The change in the LA mode frequency and the damping maximum of PbZr0.72Sn0.28O3 were much higher than those of pure PbZrO3. This was attributed to enhanced polarization fluctuations caused by increased ferroelectric distortions due to Sn substitution and the proximity to the tricritical point on the phase diagram of PbZr1-xSnxO3.

The magneto-optical activity of high quality transparent thin films of insulating EuTiO3 (ETO) deposited on a thin SrTiO3 (STO) substrate, both being non-magnetic materials, are demonstrated to be a versatile tool for light modulation. The operating temperature is close to room temperature and allows for multiple device engineering. By using small magnetic fields birefringence of the samples can be switched off and on. Similarly, rotation of the sample in the field can modify its birefringence Δn. In addition, Δn can be increased by a factor of 4 in very modest fields with simultaneously enhancing the operating temperature by almost 100 K.

PbZr1−x Ti x O3 (PZT) ceramics are one of the most known and widely used piezoelectric materials. In order to understand the origin of the high piezoelectricity it is essential to also understand its phase diagram. Many recent papers have reported the modification of PZT phase diagram based on ceramic experimental data. This is due to difficulties to get good quality single crystal samples. We have succeeded in getting a good quality single crystal with x = 0.13. Based on temperature changes of elastic properties we confirmed the existence of additional phase transition appearing in the PbZr0.87Ti0.13O3. The temperature dependence of the elastic properties was investigated by means of piezoelectric measurements and Brillouin light scattering. We discussed the correlation between anomalies of the elastic properties found in these measurements, and suggested that, except for the two well-known phase transitions, these anomalies point to another phase transition below T c. The structure and symmetry of this crystal have been tested with use of the x-ray diffraction at the room temperature.

The article reports the successful preparation of single-phase vanadium doped BaBi 2 Nb 2 O 9 ceramics. In the first part of the paper we would like to present the results of the XRD measurements, which allows us to determine the lattice parameters. The parameters do not change, which implies that the vanadium ions ordering of the crystal structure causes the decreasing number of defects. The conclusion stays consistent with the results of dielectric and thermal stimulated depolarization currents measurements, described in the second part of the paper. The pure BBN ceramics, as well as the ones modified by vanadium, show the frequency dependence of the dielectric response typical for relaxor ferroelectrics i.e. the significant reduction of SYMBOL 101 \f "Symbol" \s 12e‘ max and shift of the corresponding temperature ( T m ) towards higher values with the frequency increase. However the vanadium substitution causes a reduction of the value of parameters describing the relaxor properties.

The magneto-optical activity of high quality transparent thin films of insulating EuTiO3 (ETO) deposited on a thin SrTiO3 (STO) substrate, both being non-magnetic materials, are demonstrated to be a versatile tool for light modulation. The operating temperature is close to room temperature and allows for multiple device engineering. By using small magnetic fields birefringence of the samples can be switched off and on. Similarly, rotation of the sample in the field can modify its birefringence Δn. In addition, Δn can be increased by a factor of 4 in very modest fields with simultaneously enhancing the operating temperature by almost 100 K.

Nb-doped (Ba0.8Sr0.2)TiO3 ceramics were prepared using conventional mixed-oxide processing technique. Permittivity and loss factor were investigated as a function of temperature for various frequencies of the measuring field. The obtained results confirmed the relaxor ferroelectric behaviour of the studied ceramics, i.e. a strong frequency dispersion of the permittivity maximum and a visible shift of its temperature with frequency. Analysis of real part of permittivity allowed us to determine the value of the freezing temperature characterising the relaxor ferroelectrics. The physical processes, responsible for the relaxor behaviour of the studied ceramics are discussed.

The strong influence of bismuth additions to the lead–barium–zirconate–titanate ceramics of Ba/Zr/Ti 25/70/30 composition on grain structure, dielectric properties and dc conductivity is confirmed. The Bi-modified ceramics exhibit classical relaxor ferroelectrics (RF) behaviour similar to the other lead containing perovskites such as lead–lanthanum–zirconate–titanate-type ceramics. Dielectric relaxation typical for the ferroelectric relaxors is observed in the vicinity of diffuse ferroelectric–paraelectric phase transition. Additional anomalies in e ′ (T) curves in the low frequency range, present in the paraelectric phase for the undoped ceramics, are eliminated by the Bi admixture which also reduces the dc conductivity by three orders of magnitude. A qualitative explanation of the experimental results is presented in the paper.

PbHfO(3) is investigated theoretically and experimentally with respect to possible precursor effects starting in the paraelectric phase far above the cubic to tetragonal phase transition temperature. The theoretical modeling within the polarizability model predicts a giant softness of the system with spatially large polar and antiferrodistortive domain formation which compete with each other. These predictions are substantiated by the experiments, where the softness and the precursor effects are confirmed by birefringence, dielectric permittivity measurements and elastic properties by Brillouin scattering. The intermediate phase is found to have the polar nature confirmed by P-E hysteresis loop measurements, which is another manifestation of the competition between interrelated instabilities, namely a polar one and an antiferroelectric one.

The effects of the external d.c. and a.c. electric field on the dielectric response and relaxor behaviour of lead–barium–zirconate–titanate (PBZT) ceramics of the composition Ba/Zr/Ti 25/70/30 have been studied. The significant influence of the strength of the d.c. bias field and the amplitude of the a.c. field on the dielectric constant maximum and frequency dispersion was determined. The magnitude of the dielectric response strongly decreases under the bias field and increases with the increase of the a.c. field amplitude. All parameters describing the relaxor behaviour of the studied ceramics changed under the external d.c. and a.c. electric field. The experimental results can be explained in terms of existing models of relaxors.

Order-disorder mechanism is a part of phase transition nature in the ABO3 perovskites. It is related with the existence of polar regions, which dynamics in the electric field determines the dielectric response near T c. Temperature dependence of mechanical strain connected with polarisation change in the paraelectric phase has been investigated for the BaTiO3 and PbZrO3 single crystals. Existence of polar regions influences the electrostrictive properties and induces the piezoelectric effect in the paraelectric phase. A non-linear temperature dependence of the electrostrictive coupling between the macroscopic strain and macroscopic polarisation has been found above T c.

A ceramic of nominal formula Pb0.95Sr0.05(Zr0.53Ti0.47)0.98Nb0.02O3 has been investigated. Dielectric properties and differential scanning calorimetry tests pointed to a transformation temperature of 306??C. By means of a dynamic method the piezoelectric and complex elastic compliances for polarized ceramics have been measured as a function of temperature. The temperature dependence of the elastic properties has indicated bilinear coupling between the order parameter and strain. The unexpected existence of a pertinent piezoelectric response far above accompanied by strong changes in the elastic properties was observed. On the basis of the dielectric response and x-ray diffraction studies carried out on poled and unpoled ceramics, the influence of the compositional fluctuations and the existence of polar regions on the anomalous piezoelectric activity above were considered rather than a change of symmetry after the action of an external electric field.

In this paper the electrostrictive properties above T(emax), represented by the field-related M and polarization-related Q coefficients, have been reported for Pb(Zr(1-x)Ti(x))O(3) ceramics with x = 0.03-0.10. Among M(11)(T) and Q(11)(T) dependences, those found for Pb(Zr(0.94)Ti(0.06))O(3) have been clearly distinguished. In this case, the Q(11)(T) dependence is linear in the whole temperature range above T(emax). Experimental and theoretical analysis of the M(11)(T) dependences has shown that the phase transition to the ferroelectric phase in Pb(Zr(0.94)Ti(0.06))O(3) ceramics seems to be of the displacive type.