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Through a typical solid-state reaction followed by planetary ball milling, ABO3 structured perovskite Bi0.5Na0.5ZrO3 (BNZ) was employed as an additive to create the lead-free piezoceramic composite having compositional formula K0.47Na0.47Li0.06NbO3+(x)Bi0.5Na0.5ZrO3 where x = 0.0 wt% to 0.5 wt%. The prepared composites were characterized with the help of XRD, SEM, and FTIR. The XRD results indicated manifestation of morphotropic phase boundary (MPB), i.e. orthorhombic-tetragonal (O-T) phase boundary, for 0.4 wt% and 0.5 wt%. The SEM pictures revealed the microstructural properties of grain-grain size distribution and the average grain size of the composites. The elemental composition examination using EDAX revealed no foreign element contamination. The FTIR examination verified the development of perovskite, indicating that the BNZ has correctly fused into the KNLN matrix. The DC resistivity (ρdc) behavior was determined from IV and IR curves measured at room temperature together with varied temperature line up from 30 °C to 150 °C and a high dc resistivity ρdc of order ≈ 109 Ω cm was obtained for all the ceramics. The results have been analyzed and the mechanism pertaining to the results has been discussed in the paper. Thus the main idea was to develop a lead-free piezoceramic composite by incorporating Bi0.5Na0.5ZrO3 as an additive and investigating its effect on the above mentioned properties of the composite material. [ABSTRACT FROM AUTHOR]

In this paper, we studied the magnetism of Fe2N, using the ab initio and Monte Carlo studies. The magnetic moment and the exchange couplings are deduced by ab initio calculations. The obtained density of states is not symmetrical with respect to the axis of energy proving the ferromagnetic character of this compound. Any gap energy, at the Fermi level, is found confirming the metallic character of this compound. The Hamiltonian of this system consists of several physical parameters. Both the magnetic entropy and the maximum magnetic entropy are obtained. The relative cooling power and the magnetic hysteresis cycle are illustrated. The transition temperature TC value has been deduced and found to be about 252.01 K. This value is in good agreement with the experimental results presented. Also, we found that the magnetizations decrease rapidly to zero with increasing temperature. This is due to the ferromagnetic-paramagnetic phase transition caused by thermal energy. [ABSTRACT FROM AUTHOR]

In this paper, the shaft parts of failed machine tools were treated by laser cladding, and the shaft surface of 45# steel matrix was repaired. The microstructure, hardness and corrosion resistance of the cladding layer and quenched phase transformation zone were analyzed by metallographic microscope, Vickers microhardness tester, and friction and wear tester. The laser cladding layer was tested by friction and wear tester. The results showed that the friction coefficient of laser cladding layer was only 0.58, and it fluctuated slightly. The corrosion resistance of laser cladding layer was obviously increased. [ABSTRACT FROM AUTHOR]

In this paper, thick film antiferroelectric ceramics (1-x)(Pb0.97La0.02)(Zr0.46Sn0.48Ti0.06)O3-xH3BO3 ((1-x)PLZST-xH3BO3, x = 0–0.025) were prepared by solid state sintering and tape-casting method. The effects of boron-doping on the microstructure, dielectric properties and energy storage properties of (1-x)PLZST-xH3BO3 ceramics were investigated. Appropriate boron-doping can improve the stability of antiferroelectric phase, delay phase transition and increase saturation polarization strength. Compared with the undoped PLZST thick films, the maximum polarization intensity increased by 1.9 times and the residual polarization decreased by 37%. When x = 0.020, the maximum recoverable energy storage density is 2.74 J/cm3, and the energy storage efficiency is 88.12%. [ABSTRACT FROM AUTHOR]

In the present paper, Nd, Nb co-doped La2Mo2O9 system is investigated to understand phase transition, ionic conductivity and dielectric relaxation phenomenon. X-ray diffraction study confirms order-disorder phase transition by disappearance of peak splitting of (231) in co-doped LMX system, which is associated with monoclinic phase and is observed for LMX-Pure at around 2θ = 47–48°. In co-doped system, two dielectric relaxation peaks are observed, which are associated with diffusion process between O(1)-O(2) and O(1)-O(3) oxygen ion ←→ vacancies sites, while diffusion process O(1)-O(3) is supposed to be occurred in parent system having single relaxation peak. Thus dielectric relaxation phenomenon indicates phase transition is proceeding with static-to-dynamic disorder transition. Electric modulus data are revealed to ascertain correlation of relaxation dynamics and oxy-ion conductivity in co-doped LMX system. The extracted data of activation energy of oxy-ion conductivity at intermediate temperature range (500–700 °C) of co-doped samples is found relatively lower than that of the parent sample. The study reveals that incorporation of Nd, Nb co-doped in LMX system successfully suppress the phase transition and enhanced ionic conductivity at intermediate temperature range and found suitable as electrolytes for intermediate temperature solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

In the present paper the phenomena predicted in [2] for substances with FE and AFE phases coexisting is experimentally shown for Pb(Mg 1/3 Nb 2/3 )O 3 and Pb(B′ 1/2 B′′ 1/2 )O 3 -type compounds. Special attention is paid to analysis of their phase diagrams. The influence of external factors on the properties of these substances is considered. It is shown that all peculiarities in the behaviour of the substances in question are described on the basis of phase transitions between FE and AFE states. [ABSTRACT FROM AUTHOR]

The phase transformation mechanism and transformation path of Cu-Ni alloys is very important to study for their applications in excellent electrical properties and chemical catalysis. In this paper, the effect of compressive strain on the transformation path and mechanism of Cu1Ni3 alloy is studied by molecular dynamics simulations. The simulation results reveal that the transformation path of alloys is from Fcc-Bcc-Hcp phase to other phase (amorphous state). The simulations not only revealed the processes of atomic displacements and pair correlation function during the transformation, but also elucidated the underlying mechanism of the transformation at the atomic level. The mechanism of phase transformation could be the lattice reconstruction caused by lattice sliding and stretching. The simulation results provide a clear landscape on the transformation mechanism, facilitating our comprehensive understanding on the phase transition in the Cu-Ni system. [ABSTRACT FROM AUTHOR]

Ferroelectric materials with high Curie temperatures, TC, and tuning of the TC over a large temperature range are very important for the basic sciences and engineering. This paper reviews the various types of high-temperature ferroelectrics with perovskite, bismuth layered, tungsten bronze, and perovskite slab structures, especially Sr2Nb2O7 with TC = 1342 °C and its family. The lattice instability of the high-temperature ferroelectric phase transitions is also discussed. The superior tunability of the TC is achieved by the substitution of cations at the A- and B-sites in the perovskite-like structures. The variation of the soft optic and relaxation modes and elastic anomalies related to structural phase transitions were discussed in relation to the A- and B-site substitutions of oxygen octahedral ferroelectrics, especially Ba2NaNb5(1-x)Ta5xO15 with a tungsten bronze structure and (BaxSr1-x)2Nb2O7, Sr2(Nb1-xTax)2O7 with the perovskite slab structure. [ABSTRACT FROM AUTHOR]

In this paper, the development in the field of ferroelectrics is reviewed by summarizing the topics in the field as presented at the International and European conferences on Ferroelectrics. While from the very beginning in 1966 until now fundamentals in ferroelectrics always played a significant role, it is shown that the topics considerably broadened over the years and are nowadays barely overlooked. Polarity dominated the field from the beginning; however, now its combination with more exotic properties like skyrmions, magnetism, functional domain walls has entered the stage and substantially enlarge the field of applications. [ABSTRACT FROM AUTHOR]

In the present paper the phenomena predicted in [1] for substances with coexisting FE and AFE phases coexistence is experimentally shown. The examples of PZT-based solid solutions are investigated. The solid solutions for which FE and AFE states have equal or close energy stability possess the following experimental properties: - a high degree of (paraelectric) PE phase transition diffuseness; - an essential dispersion of permittivity in the region of diffuse maximum of the dependences ℇ′(T) and ℇ′′(T) and fulfilment of the Fogel-Fülcher law; - an increase of the measuring AC field amplitude E 0 leads to a linear decrease of T′ m and to an increase of ℇ′(T′ m ); the tangent of T′ m (E 0 ) dependence decreases with an increase of AC field frequency; - the presence of effects which point to the existence of polar phase domains at temperatures essentially higher than T′ m and T′′ m ; - dependence of their properties on the sample's history; - a long-duration relaxation. [ABSTRACT FROM AUTHOR]

Ferroelectrics are usually defined as polar materials that display polarisation hysteresis. This is a functional definition. A structural definition exists too, based solely on symmetry arguments. The structural definition, useful e.g. for design of new materials, says that a ferroelectric is a material that underwent a phase transition from a parent higher-symmetry phase into a ferroelectric phase, such that the polar directions in the ferroelectric phase are linked to each other by lost symmetry operations of the parent phase. Ferroelectrics are discussed in this paper from a structural point of view. The structural definition helps also in clarifying the relationship between ferroelectrics and antiferroelectrics, conducive for the design of new antiferroelectrics or tuning of existing ones. Relaxor ferroelectrics are discussed too, in the structural context. The contemporary material (Na1/2Bi1/2)TiO3is then used to illustrate the subjects discussed, the existing knowledge, and the missing understanding. This paper, on the occasion of the 500thvolume of the journal Ferroelectrics has the limited scope of (a) reemphasizing the structural aspects of ferroelectricity and (b) serving as a primer on ferroelectric materials for the novice. [ABSTRACT FROM AUTHOR]

In this paper, the study of the dynamic pyroelectric effect under different powers of modulated heat flux in deuterated triglycine sulfate (DTGS) near the Curie point is presented. It was found that pyroelectric coefficient was essentially dependent on the power of the modulated radiation, especially in the phase transition region. It is shown that a tertiary pyroelectric effect makes an additional contribution to the pyroelectric response observed in TGS group crystals near phase transition region. The tertiary pyroelectric effect is caused by a nonuniform distribution of piezoelectric coefficients in the samples as a result of temperature gradient presence. [ABSTRACT FROM AUTHOR]

The paper is devoted to study of domain structure and birefringent properties of [(CH3)2CHNH3]4Cd3Cl10:Cu (IPACCC) crystals in the region of their high temperature phase transitions. On the basis of investigations of the optical birefringence temperature increments there were detected the phase transitions at T1 = 359 K and T2 = 293 K (in a heating run). On the basis of the Landau theory analysis the latter transition was related to the first order close to the second order one. Using AFM the domains in the ferroelastoelectric phase lying below T2 were visualized for the first time. It was found that the symmetry of phases in IPACCC is the same as in initial IPACC crystal without copper adding, although both high temperature phase transitions were found to be a little shifted by temperature. [ABSTRACT FROM AUTHOR]

The main objectives of the paper were to study the anomalies in the electrophysical parameters of the transparent ferroelectric ceramics of the PLZT (X/65/35) system near the diffuse phase transition, and to measure the complex sets of dielectric, elastic and piezoelectric parameters of those materials over a wide frequency range. The ferroelectric ceramics of the system (Pb1-xLax)(Zr0,65Ti0,35)O3 with lanthanum content were chosen as the object of the study. The experimental samples of ferroelectric PLZT ceramics were obtained by the hot pressing method. The complex parameters of the experimental samples were measured by the piezoelectric resonance analysis method using the software package PRAP. The sets of complex elastic, dielectric and piezoelectric parameters of PLZT (6.5/65/35) ceramics were obtained. The anomalies in the behavior of surface acoustic waves velocity and attenuation for PLZT (7.5/65/35) ceramics near the temperature of diffused phase transition were found and discussed. [ABSTRACT FROM AUTHOR]

Dielectric properties of 2,3,6,7,10,11-hexahydroxytriphenylene tetrahydrate crystallites are examined in this paper. We observe a first order, order-disorder phase transition at a temperature of 251 K. The frequency dependence revealed four relaxation regions, where two relaxations follow the Arrhenius law with activation energy of 300 meV. Our investigation shows the experimental data below the phase transition to follow the Curie-Weiss law, however, ferroelectric ordering is not observed. [ABSTRACT FROM AUTHOR]

The paper presents results of studies on phase transitions in RbIn(MoO4)2at 163 and 143 K obtained using the electron paramagnetic resonance and polarised light microscopy. It has been found that the ferroelastic phase transition observed around 143 K is split into two closely situated transitions separated by a temperature interval of around 0.2 K. It has been found that these phases coexist in a temperature range of few dozen degrees. [ABSTRACT FROM AUTHOR]

The paper reviews the results of our studies concerning the ferroelastic domain structure in the crystals exhibiting superprotonic conductivity. We would like to show the ferroelastic domain structure and its temperature behaviour in solid acids which belong to the family of crystals with a general formula MxLiyHz(XO4)(x + y + z)/2 (M = Rb,K,Cs,NH4; X = S and Se). For the majority of crystals, which belong to that family, the transition to the phase with high proton conductivity is simultaneously the ferroelastic-paraelastic one. However, this does not apply to all crystals of the family. Therefore, a question arises about the role of the phenomenon of ferroelasticity in the superprotonic phase transition. Depending on x,y and z, there are different groups of crystals. Our paper presents the results of temperature evolution of ferroelastic domain pattern at ferroelastic-superprotonic phase transitions as well as at other structural phase transitions, which appear in different crystal groups. [ABSTRACT FROM AUTHOR]

This paper reviews the spontaneous polarization of ferroelectric ceramics and its variations with applied electric field, stress and temperature, especially at induced phase transitions. Normally, there are two kinds of field dependence of the induced polarization, the linear and nonlinear dependence. In this paper the nonlinear relationship will be emphasized. The application of these ceramics for underwater transducers, shock wave power generators, pyroelectric energy converters and pyroelectric voltage transformers are listed. [ABSTRACT FROM AUTHOR]

The ferroelectromagnet ceramics Pb(Fe0.5Nb0.5)O3 ( PFN) has been synthesized by solid state reaction technique. The measurements of the dielectric constant and loss as a function of temperatures and frequencies determined the relaxor ferroelectric behavior of this compound. The X-ray diffraction pattern shows the phase purity and the SEM images of fractured surface demonstrate the granular properties of the materials. In this paper, we study the magnetic field effect on the dielectric properties of PFN by measuring the dielectric constant and loss at different applied magnetic fields and different temperatures. [ABSTRACT FROM AUTHOR]

We have shown that in the chromium oxide the components of the tensor of magnetoelectric susceptibility α 33 ( T ) in the original phase and α 31 ( T ) in the spin-flop phase exhibit similar temperature dependencies. It's proved in the present paper that noted above behavior of these components can be explained in the framework of the phenomenological theory if one takes into account invariants of the third and fifth order of magnitude in the components of the antiferromagnetic vector in the phenomenological thermodynamic potential with explicitly separated exchange and relativistic terms. Also, the form of thermodynamic potentials elaborated in this paper suggests that the transition to the spin-flop phase in the chromium oxide is incomplete and α 33 cannot be equal to zero in the spin-flop phase. [ABSTRACT FROM AUTHOR]

In the present paper, we have investigated the high-pressure structural phase transition of plutonium bismuthide. We studied theoretically the structural properties of this compound (PuBi) by using the three-body potential model (TBI). This compound exhibits first order crystallographic phase transition from NaCl (B1) to body centred tetragonal (BCT) phase at 9.5GPa. The phase transition pressures, associated volume collapse and elastic behaviour of PuBi obtained from three body interaction (TBI) model show a good agreement with available experimental data. [ABSTRACT FROM PUBLISHER]

Sodium metavanadate has pyroxene-type one dimensional VO4-tetrahedral chains, which is analogous to the SiO4-chains in Bi2SiO5. Although it is known to undergo ferroelectric phase transition, its mechanism has not been clarified. This paper shows the spectroscopic results of simultaneous measurement of Raman/Brillouin scattering by utilizing ultra-narrowband holographic notch filters. The spectroscopic anomalies accompanying to the phase transition were observed for the first time in both Raman and Brillouin regimes. [ABSTRACT FROM AUTHOR]

In this paper we report on the investigation of longitudinal ultrasonic wave attenuation, velocity and ultrasonically induced piezoelectric voltage in P(VDF-TrFE) composites with fillers of conductive carbon nanotubes (CNT). Moreover, temperature dependences of ultrasonic attenuation in the composites were shown to be sensitive to thermal cycling over the ferroelectric phase transition. [ABSTRACT FROM AUTHOR]

Temperature dependences of Brillouin light scattering spectra from Ba0.5Sr0.5 Nb2O6 (SBN 50) film were obtained. The deviations of the Brillouin shift dependence from linear near ferroelectric phase transition are due to electric fields in the local regions with symmetry breaking. A maximum of Brillouin line width is more than twice of the corresponding width in a bulk crystal of the same composition. This broadening is attributed to the confinement of the acoustic phonons. Optical second harmonic generation measurements (SHG) showed that the transition from the polar to the nonpolar phase occurred at a temperature characteristic of SBN-50. [ABSTRACT FROM AUTHOR]

In this paper the investigation of relaxor ferroelectric PbFe0.5Nb0.5O3has been carried out using the method of X-ray diffraction, magnetic and dielectric measurements over a wide range of temperatures and frequencies. It has been shown that in single crystals there is high-temperature phase transition from the ferroelectric phase to the cubic phase at a temperature of 367 K. The anomalies detected in the dependences of magnetic susceptibility χ (T) and the magnetic moment m (T) in polycrystalline at room temperature and above were found to be correlating with the anomalies detected by structural, EPR spectroscopic and dielectric measurements. [ABSTRACT FROM AUTHOR]

This paper presents a systematic investigation of the dielectric and pyroelectric properties of PMN-29PT single crystals, oriented and poled along three different crystallographic directions, <001>, <011> and <111>as a function of temperature and frequency. Dielectric measurements were performed over a temperature range of 300 K–500 K and at frequencies of 20 Hz–1 MHz. During the heating cycle, two phase transitions are detected: one at ~380 K from rhombohedral to tetragonal phase, another at ~410 K from tetragonal to cubic phase. However, during the cooling cycle only one smeared phase transition is observed, i.e. phase transition from cubic to rhombohedral phase. Pyroelectric measurements were performed from 220 K to 420 K during the heating cycle. The variations of pyroelectric coefficients with temperature shows two maxima, one at 370 K and another at 400 K for the <111>- and <011>-oriented crystals, respectively, while only one maximum is observed at 360 K for the crystal oriented along the <001> direction. [ABSTRACT FROM AUTHOR]

In this study, we aim to investigate theoretically the critical characteristics of spin −1/2 four-leg nanotube for the nanotechnology applications. The Ising model simulated by Monte Carlo simulation is adopted with the first exchange coupling J , the second exchange coupling between the second nearest neighbor atomic spins J ′ and the transverse exchange coupling J z , and the external magnetic field h as parameters. Herein, we examine the local properties of spin −1/2 four-leg nanotube by analyzing the magnetization, susceptibility and hysteresis loop behavior as function of J ′ , J Z and h. The obtained results show that the isotropic ‐ 1 / 2 four-leg nanotube Ising model presents critical behavior at ferromagnetic to paramagnetic phase transition where the Curie temperature T C increases according to vertical and second nearest neighbor exchange coupling. Furthermore, under external magnetic field, the magnetization keeps the second order transition and the magnetic susceptibility declines with the increase of applied external magnetic field value. In addition to that, we have found single ferromagnetic hysteresis loops, for which the shape increases by increasing the second nearest neighbor exchange coupling when T = J. Finally, the critical temperature shows perfect mirror symmetry relative to the vertical and increases with the second nearest neighbor exchange coupling. [ABSTRACT FROM AUTHOR]

This study investigates the dielectric properties, including dielectric constant (ɛ′), dielectric loss (ɛ″), tangent delta (tan δ), and AC conductivity (σac), of PVA/Y2O3 polymer nanocomposites (PNCs). The dielectric behavior of the PNCs was examined as a function of frequency and temperature. The results revealed that the addition of Y2O3 nanoparticles to the PVA matrix influenced the dielectric properties of the composites. In contrast to pure PVA, the PVA/Y2O3 PNCs with a 15 wt% Y2O3 loading exhibited high values of ɛ′, ɛ″, tan δ and σac are 647.49, 1607.48, 9.70 and 1.024 × 10−5, respectively, at low frequency and at particular temperature. Furthermore, the electrical properties of PVA/Y2O3 PNCs were also investigated using the Cole-Cole plots. These plots provide valuable insights into the complex impedance behavior and allow for comprehensive understanding of the electrical response of the nanocomposites. [ABSTRACT FROM AUTHOR]

The ferroelectric to relaxor crossover of A(B1-xB′x)O3-type perovskites with increasing x is discussed from the order-disorder point of view for Ba(Ti1-xSnx)O3(BTS-x) as an example. The polar short-range order of the disordered off-centred Ti ions in BaTiO3increases with decreasing temperature, leads to nucleation and, finally, to the long-range ordered ferroelectric phase. This process becomes impeded with increasing content of Sn ions x that make the nucleation and the transition more and more incomplete and finally impossible (relaxor). The composition BTS-0.1 corresponds to PMN-PT and PZN-PT systems near the “morphotropic phase boundary” where the temperature Tmof maximum permittivity is mainly determined by nucleation rather than by a transition to tetragonal long-range order. This is concluded from different electromechanical properties and confirmed by additional aging experiments on BTS-0.1. Other reasons for incomplete transitions to long-range order are not discussed in this paper. [ABSTRACT FROM AUTHOR]

In this paper, we report observation and study of transformation of the vibration shapes in resonances of micromachined piezoelectric circular membrane. Micromachined piezoelectric zinc oxide circular membrane was fabricated and the vibration shapes of the membrane at different frequencies were measured by a scanning Mach-Zehnder interferometer. The finite element analysis with a commercial software ANSYS was performed to study the vibration characteristics of the circular membrane. The result shows that the transformation of the vibration shapes in resonances of the circular membrane could be influenced by its asymmetrical characteristics. [ABSTRACT FROM PUBLISHER]

This paper suggests the design in rectifier and array configuration for an impact-based piezoelectric energy harvesting (PEH) system, to investigate the charging efficiency. In the design of the rectifier, it is suggested that rectifying the signal from each piezoelectric module separately generates more electrical energy and charges a capacitor faster than using a single rectifier for all modules connected in series. In the structural design, the array was designed into two conditions: impacted simultaneously and impacted sequentially with a phase difference (30°, 60°, 90°, 120°, 150° and 180°). We show that when impacted sequentially with a phase difference, this allows faster charging rates of energy harvesting. Additionally, distribution of the torque required to transform the piezoelectric modules was found to be another advantage from this condition. These results could be used in the design of more-efficiently-charging impact-based PEH system. [ABSTRACT FROM AUTHOR]

This paper highlights the structural, dielectric and pyroelectric properties of two complex tungsten bonze ceramics (K2Pb2Pr2W2Ti4Nb4O30and K2Pb2Pr2W2Ti4Ta4O30) which were prepared by high temperature mixed oxide method. Room temperature X-ray structural analysis confirms the formation of the compounds in single phase. SEM micrographs show uniform distribution of densely packed rod like grains. Variation of dielectric parameters with temperature and frequency shows the phase transition at 350°C and 426°C for the respective samples. Temperature dependent hysteresis loop confirms the existence of ferroelectricity in the materials. The current variation with voltage at different temperatures shows the semiconductor like behaviour of the materials. The temperature dependent dc conductivity follows the Arrhenius equation, and reveals the negative temperature coefficient of resistance (NTCR) behaviour of the materials. The current (for a fixed voltage) variation with temperature shows that the materials have high pyroelectric co-efficient and figure of merit, thus making them useful for pyroelectric sensors. [ABSTRACT FROM AUTHOR]

In this paper, results of new infrared FIR-MIR measurements (wavenumber range of 4000–100 cm−1) in the range of the temperature 300 ÷ 8 K of the BiFeO3 ceramic are presented. Below 200 K only one symmetric band at ca. 800 cm−1 is visible. The full width at half maximum of this band decreases exponentially on cooling. The shape of the band at ca. 545 cm−1connected with A1 (TO) mode also changes between 60–40 K, this is in the vicinity of the phase transition at 50 K. Initially a broad band reveals its components as shoulder bands. Theirs FWHM decrease with cooling. [ABSTRACT FROM PUBLISHER]

The present paper deals with systematic study of dielectric characteristics and a.c conductivity of single crystal of NiTiO3 above room temperature. These crystals were prepared by high temperature flux technique. Dielectric constant, tangent loss and conductivity studied on these crystals strongly dependent on temperature and frequency of the applied a.c field, the variation depending on range of temperature and frequency. The appearance of pronounced peak at 773°K in the curve of dielectric constant, loss tangent and conductivity versus temperature indicates ferroelectric phase transition. The increase of conductivity with increase of temperature suggests semiconductor behaviour of this material. The lnσa.c versus temperature plot indicates conduction mechanism to be hopping model. The temperature variation of conductivity confirms to Arrhenius law σ = σ0exp. [-Ea/RT], where E is activation energy per mole required for hopping process and σ0 is free space permittivity. The magnitude of activation energy is found to be greater than 0.2 eV per molecule for this crystal which suggest that conduction mechanism is due to hopping. [ABSTRACT FROM AUTHOR]

The paper presents results of studies of the dielectric response and structure of the PbCo1/3Nb2/3O3 (PCN) crystal. Analysis of the dielectric response at frequencies ranging from 10 Hz to 50 kHz has revealed a considerable dispersion in a wide temperature interval. Anomalies in the temperature dependences of ε' and ε'' in the vicinity of 350, 250, and 130 К have been observed. It is shown that the anomaly near 250 K can be attributed to the transition into a relaxor ferroelectric state, whereas the anomaly at 130 K occurs nearby to the antiferromagnetic phase transition. The behaviour of the dielectric response in the vicinity of 350 К requires further studies. The PCN crystal structure at room temperature has been refined. [ABSTRACT FROM AUTHOR]

The phase composition and microwave dielectric properties of xLnAlO3-(1-x)Ln1/3NbO3 (Ln: LA, Nd, 0 ≤ x ≤ 0.9) have been investigated by XRD, EDS, SEM and network analyzer in this paper. All samples with x>0 exhibited multiple phases. Both of dielectric permittivity and temperature coefficient of resonant frequency decreased with the increase of x when x<0.4 and varied little with further increasing x. Q × f value increased with the increase of x. Good combined microwave dielectric properties could be obtained for the samples with x = 0.9: εr = 22.4, Q × f = 49439GHz, τf = -30ppm/°C for La-series and εr = 21.1, Q × f = 54540GHz, τf = -44.8ppm/°C for Nd series. [ABSTRACT FROM AUTHOR]

This paper reports a ferroelectric-to-paraelectric (FE-PE) two-step transition in the acceptor-doped ferroelectric systems. In ceramic samples, the DSC peak as well as the dielectric permittivity peak exhibits a split after aging at DSC peak temperature. Such phenomenon also exists in the grain-boundary-free single crystal samples; this excludes the possibility of a grain boundary effect. Moreover, the in-situ optical microscopy observation during heating proves that such peak split is due to a two step FE to PE transition. The microscopic explanation is given based on the symmetry-conforming properties of point defects. [ABSTRACT FROM AUTHOR]

In a recent paper, the modified model by P. Weiss was applied to ferroelectrics. Typical ferroelectric properties could be simulated. A further generalization of the Weiss model is the assumption of a power law feedback with an exponent κ between the polarization of the permanent dipoles and the local field. The Weiss model is included for the exponent κ = 1 and we obtain a second-order type phase transition. For values κ > 1 the simulations yield first-order type phase transitions whereas we obtain diffusive-type phase transitions for values κ < 1. [ABSTRACT FROM AUTHOR]

The paper reports the results of the temperature dependence measurements of the specific heat for a SrTiO3 thin (104 nm) film deposited on a DyScO3 substrate. Two anomalies of the specific heat have been observed. They can be associated with the strain-induced ferroelectric phase transition (at 304K) and the shifted antiferrodistortive structural phase transition (at 173 K). [ABSTRACT FROM AUTHOR]

In this paper the results of dielectric investigation of nanoconfined NaNO2 is presented. The phase transition is shifted to lower temperatures. Only one phase transition can be seen in the dielectric spectra and the intermediate incommensurate phase is suppressed. The increase in the frequency dependent dielectric permitivity on heating is mainly the result of a conductivity effects. The relaxational soft mode contribution is as well present, but is small as compared to the conductivity contribution. Such huge conductivity is caused by premelting phase, which is visible even at temperatures below the phase transition [ABSTRACT FROM AUTHOR]

In this paper we report the dielectric investigation results of BaBi2Ta2O9 (BBT) ceramics performed in a broad frequency and temperature range. It is shown, that this ceramics possesses the ferroelectric relaxor behaviour. A very diffuse phase transition is observed in the whole measured temperature range and the dielectric permittivity exhibits a strong dispersion in the frequency range from Hz to microwaves where the maximum of permittivity, Tmax, shifts to higher temperature as the frequency increases. From the frequency dependences of the real and imaginary parts of dielectric permittivity the parameters of dielectric dispersion have been calculated. [ABSTRACT FROM AUTHOR]

This paper presents the theoretical calculation of energy levels of the valence bands and bond orders of the SbSBr single crystals using the molecular cluster model consisting twenty SbSBr molecules. The theoretical calculation revealed that the ferroelectric phase transition changes the bond orders and shift valence bands. Results of theoretical calculations of averaged total density of states of SbSBr molecular cluster are compared with the experimentally results of X-ray photoelectron spectroscopy (XPS) of SbSI crystals, because that SbSI and SbSBr crystals have isomorphic electronic structure. [ABSTRACT FROM AUTHOR]

In this paper effects of lead doping on the lattice response and phase transitions of bismuth-layered structure Sr 1-x Pb x Bi 2 Nb 2 O 9 (x = 0.0 to 0.5 in steps of 0.1) ferroelectric ceramic are reported. It is observed that structure attains more tetragonality with doping of lead up to 40%. Increased orthorhombic distortion is also observed. Curie temperatures of all samples were measured and the phase transition is explained in terms of lattice response of these ceramics. Sample with x = 0.5 shows decreased tetragonal strain and Curie temperature. Also, relationship of polarization with lattice response is discussed. [ABSTRACT FROM AUTHOR]

Optical second harmonic generation (SHG) is shown to be a powerful tool for characterizing the main properties and processes in ferroelectrics. In this paper first of all a general phenomenological description is given in order to express the SHG field (intensity) in terms of dielectric polarization. Then specific experimental techniques are described to study crystalline and domain structure of thin ferroelectric films, the bulk and interface ferroelectric and structural phase transitions. Finally SHG is applied to characterize ferroelectric nanostructures and fast polarization switching on nanosecond and picosecond time scales. [ABSTRACT FROM AUTHOR]

The dynamic mechanism of the ferroelectric phase transition in SrTi(16O1-x18Ox)3induced by the isotope exchange of18O for16O is proposed. This mechanism is based on the electron-lattice p-d coupling, TO and TA phonon-phonon interactions and the quantum fluctuations (zero-point motion). The lowest zone center modeF1u(Γ) in the cubic phase splits intoA2u+Eumodes in the tetragonal phase and theEumode is the ferroelectric soft mode in SrTi18O3. It is shown that the application of hydrostatic pressure on the ferroelectric SrTi18O3depresses the transition temperature down to 0 K abovepc≈0.7 kbar through the electron-lattice strain coupling.∗Paper Originally Presented at 10th European Meeting on Ferroelectricity, Cambridge, U.K., August 3–8, 2003. E-mail:konsin@fi.tartu.ee [ABSTRACT FROM AUTHOR]

The model of static charged clusters, which adequately describes the dielectric hysteresis and permittivity of disordered ferroelectrics with non-isovalent impurities, has been proposed. The main result of paper is modified Landau-Ginzburg-Devonshire equation can be applied to the bulk ferroelectric materials with improper conductivity and movable charge fluctuations near the impurity centers. [ABSTRACT FROM AUTHOR]

Recent theoretical investigations predict that the thermal filling of trap centers could lead to an intricate sequence of phase transitions with unstable boundary state between the phases. This fact has motivated the experimental study of ferroelectric phase transitions in TlInS2 〈Mn〉 composites where the cationic impurities can form the capture levels (traps) at the bottom of the conduction band. In this paper the results of experimental investigation of dielectric, polarization and pyroelectric properties of TlInS2 〈Mn〉 composites are presented. It was shown that TlInS2 〈Mn〉 composites display all peculiarities that are typical for relaxor ferroelectrics. [ABSTRACT FROM AUTHOR]

In this paper a variety of architectures of self-assembled halo-coordinated MX 6 octahedra in ferroelectric halogenoantimonates(III) and halogenobismuthates(III) is illustrated. The dielectric properties of a new ferroelectric [4-NH 2 C 5 H 4 NH][SbCl 4 ] are presented. The para-ferroelectric phase transitions mechanism (C2/c → Cc) at T c = 270.5 K is discussed. The phase situation in the [4-NH 2 C 5 H 4 NH][MX 4 ] (where M = Sb, Bi and X = Cl, Br) family is compared. [ABSTRACT FROM AUTHOR]

The paper deals with phenomenological treatment of Lead Zinc Niobate--Lead Titanate (PZN:PT) crystals. Polarization and weak field permittivity as functions of temperature and bias electric field throughout the whole phase transitions range are of particular importance for the PZN-PT composition's behaviour close to the morphotropic phase boundary (MPB). The effect of DC bias field on phase transitions in PZN:PT solid solutions near the MPB was studied. A phase transition induced by electric field and associated changes in dielectric properties of PZN:PT were observed for different compositions of 4.5% and 8% PT. Relaxation behaviour was observed, too. [ABSTRACT FROM AUTHOR]

This paper presents studies of lattice dynamics of a crystal of Cs 5 H 3 (SO 4 ) 4 · x H 2 O (PCHS) and its deuterated analog Cs 5 D 3 (SO 4 ) 4 · x D 2 O (DPCHS) in wide temperature and frequency ranges by dielectric spectroscopy and modulated temperature differential scanning calorimetry. It is shown that deuteration of PCHS gives rise to an additional structural phase transition at T c3 ≈ 250 K. The temperature of the isostrctural phase transition T c2 (372 K for PCHS and 370 K for DPCHS) has been determined more accurately. It has been found that deuteration does not suppress phase transition at T c2 . The temperature dependence of dielectric response is analyzed. [ABSTRACT FROM AUTHOR]