Heat capacity and thermal conductivity of multiferroics Bi1-xPrxFeO3

The heat capacity and thermal conductivity of multiferroics Bi1–xPrxFeO3 (0 ≤ x ≤ 0.50) has been studied in the temperature range of 130–800 K. A slight substitution of praseodymium for bismuth is found to lead to a noticeable shift of the antiferromagnetic phase transition temperature whilst the heat capacity increases. The temperature dependences of the heat capacity and thermal conductivity exhibit additional anomalies during phase transitions. The experimental results suggest that the excess heat capacity can be attributed to the Schottky effect for three-level states. The basic mechanisms of the heat transfer of phonons are highlighted and the dependence of the mean free path on temper…

Description of Relaxor State in Na1/2Bi1/2TiO3-SrTiO3-PbTiO3 System of Solid Solutions

Vogel-Fulcher law, traditionally applied to describe dispersion of dielectric permittivity in relaxor ferroelectrics, requires introduction of two different relaxation mechanisms above and below freezing temperature correspondingly. Extending distribution function of relaxation times, previously known for low-temperature region, allows creating common description of relaxation in all range, where distribution function of relaxation times can be regarded as wide, without freezing at certain temperature.

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 concent...

Relation of Dielectric Permittivity and Electric Field Dependence of Polarization in Some Relaxors with Perovskite Structure

The dielectric nonlinearity is studied in ferroelectric relaxors 0.92PbMg1/3 Nb2/3O3-0.08PbTiO3, 0.4Na1/2Bi1/2TiO3-0.5SrTiO3-0.1PbTiO3 and Pb0.9075La0.0925 (Zr0.65Ti0.35)0.9775O3. It is shown that above the temperature of dielectric permittivity maximum nonlinearity of dielectric permittivity corresponds to electric field dependence of polarization. The influence of electric field on distribution of relaxation times is studied below the maximum of dielectric permittivity. The role of internal bias field in Pb0.9075La0.0925(Zr0.65Ti0.35)0.9775O3 ceramics is discussed.

Interface Effects in Ferroelectric Thin Films

Dielectric, ferroelectric and piezoelectric characteristics in sol-gel derived and pulsed laser deposited (PLD) lead zirconate titanate (PZT), La modified lead titanate (PLT) and zirconate titanate (PLZT) ferroelectric thin films are investigated focusing on maintenance of thin film ferroelectric (FE) properties in a variety of thin film-electrodesubstrate interfaces. Interferometric studies of piezoelectric response of the heterostructures were performed with respect to a DC electrical bias and AC measurement frequency. The asymmetry of piezoelectric coefficient (d33) hysteresis, diminished values of d33, frequency-displacement and spot size — deformation behaviour in the ferroelectric het…

Dielectric and Polarization Properties of Na0.5Bi0.5TiO3-BaTiO3Solid Solutions with Na and K Niobates

The role of substitution in A- and B-sites of perovskite ABO3 structure in phase transitions is evaluated, comparing (1-y)(0.939Na0.5Bi0.5TiO3-0.061BaTiO3)-yKxNa1-xNbO3 solid solutions with x = 0.0, x = 0.5 and x = 1.0. The influence of deviation from a stoichiometric Na/Bi ratio is also studied. The influence of K0.5Na0.5NbO3, NaNbO3 or KNbO3 reduces mainly to suppressing of ferroelectric properties, like in other perovskite ferroelectrics where Ti is replaced by Nb, and development of the relaxor state. Besides the frequency-dependent dielectric permittivity, the relaxor state in the studied compositions is characterized also by a temperature dependence of critical electric fields, corres…

PHASE TRANSITIONS IN Na1/2Bi1/2TiO3-SrTiO3-PbTiO3 SOLID SOLUTIONS

ABSTRACT Studies of nature of polarization in ternary solid solutions of Na1/2Bi1/2TiO3-SrTiO3-PbTiO3 were done, using measurements of dielectric properties and polarization hysteresis loops. Various stages of relaxor behavior depending on concentration of PbTiO3 were established and compared with other known ferroelectric relaxors.

High Electromechanical Coupling in Relaxor Pb(Sc<sub>1/2</sub>Nb<sub>1/2</sub>) O<sub>3</sub> - PbTiO<sub>3</sub> System Hot-Pressed Piezoelectric Ceramics

Microscopy studies of the surface of high-temperature superconductor films

The surface morphology is studied by use of optical and electron microscopes with respect to production regime (rate and temperature of crystallization) of the 50 - 125 micrometer thick doped YBa 2 Cu 3 O 7 films obtained by Stokes sedimentation on SrTiO 3 ceramic substrate (size 20 mm by 5 mm by 0.5 mm) and firing in air or oxygen following the MTG procedure, performed in the gradient tube furnace. Evolution of thick film structure with regard to temperature and cooling rate is studied.

Modified YBCO superconductor-ferroelectric composites: Bulk materials and thick films

Bulk samples and 50–125 μm thick films of (1-x)YBa2Cu3O7−δ-xBaTiO3 (0⩽x⩽0.12 by weight) composites have been synthesized, the films being obtained by Stokes sedimentation on SrTiO3 ceramic plates and firing in oxygen by Melt Textured Growth techniques. The phase composition and texture have been studied by X-ray diffraction and microstructure. Resistance and magnetic susceptibility of prepared samples have been measured.

Evolution of dielectric permittivity under applied field in PLZT 8.3/70/30 ceramics

Abstract The jump of dielectric permittivity as function of bias field applied after various duration of storage at the measurement temperature is investigated. The influence of storage time on ϵ(E=) depends on the value of bias field and frequency of measuring field. It is found that ϵ(E=) depends on the path of how particular field value is reached.

Structure and Physical Properties of Na1/2Bi1/2TiO3-CdTiO3Solid Solutions

Behaviour of ferroelectric properties in Na1/2Bi1/2TiO3-CdTiO3 solid solutions correlates with dependence of lattice symmetry versus concentration of constituents. However, some overlapping is observed in concentration range close to the morphotropic phase boundary. The properties of dielectric permittivity, characteristic for relaxor ferroelectrics, diminish, if concentration of CdTiO3 increases, but it is not influenced by the change of crystallographic symmetry. The electromechanical properties are mostly pronounced in the range of cubic-tetragonal morphotropic phase boundary.

Study of Tetragonal Phase in 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3Solid 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…

Pulsed laser deposition of relaxor ferroelectric films

Heterostructures of perovskite relaxor ferroelectric (RFE) thin films onto La 0.5 Sr 0.5 CoO bottom electrode layers were grown by pulsed laser deposition on MgO(100) crystal substrates. The films were highly oriented, with (h00) planes parallel to the substrate surface, and demonstrated good dielectric and ferroelectric quality at room temperature. The studies of the dielectric properties of the films over the frequency range of 20 Hz....100 kHz and over the temperature range of 0...350°C revealed relaxor type behavior in the films. A diffuse ferroelectric phase transition and a shift of the maximum dielectric permittivity towards higher temperatures with increasing frequency were observed…

Phase transitions and properties of perovskite ferroelectric ceramics and films for certain applications

Abstract The structure-properties relationships and phase transitions in perovskite ceramics, and films of PLZT, PLZST, PST, PSN, PMNT compounds are discussed with regard to ordering, relaxor behaviour, pronounced ferroelectric, electromechanical and electrocaloric properties. The theoretical approach is extended to the time dependent Ginsburg-Landau model. The evolution of dielectric properties in relaxors after the change of temperature and electric field creating an increase of dielectric permittivity is found to follow a logarithmic law of decay. A strong electromechanical response is observed in a number of thin films of different compositions.

Evolution of dielectric properties in transparent PLZT 8.3/70/30 ceramics at the diffused phase transition

Abstract The time evolution of dielectric properties after a temporary change of temperature and electric field is investigated. It is found, that below the temperature of ˛' maximum Tm the change of temperature and electric field creates an increase of dielectric permittivity followed by logarithmic decay when the change of these parameters is finished. At every temperature the dielectric properties are characterized by a unique ˛'(t) independent on previous thermal history. If the applied electric field is E< Ec, the state of polarization is not affected. The dependence on dielectric constant of storage time under field as well as field intensity is determined.

Improvement of solid state Er:YAG pulse laser performance for use in medicine

The large quadratic electro-optic effect of PLZT ceramics allows to design small size modulators for the solid state infrared Er:YAG laser (lasing at (lambda) equals 2.94 micrometers - the most pronounced absorption band of water), which has found application in medicine for efficient ablation of hard and soft tissues. In the free-running mode, the Er:YAG laser emits spikes that form the pulse envelope with duration of 150 - 800 microsecond(s) . An extracavity PLZT 8.5/65/35 ceramics modulator (aperture of 4 X 6 mm2 and length of 18 mm) was used to obtain (Pi) -shaped segments with the rise and decay times less than 5 microsecond(s) . That allows to reduce considerably the fraction of the p…