Structure,Ferroelectric, and Magnetoelectric Properties of Bulk PZT–NiFe<Subscript>1.9</Subscript>Co<Subscript>0.02</Subscript>О<Subscript>4 – δ</Subscript> Composites

The phase composition, microstructure, and dielectric, ferroelectric, magnetic, and magnetoelectric properties of bulk ceramic (1 – x)PZT–xNiFe_1.9Co_0.02О_{4 – δ} composites with 3–0 connectivity have been studied. Using X-ray diffraction and electron microscopy, it has been established that the ferrimagnetic (spinel- like) and ferroelectric (tetragonal perovskite-like) phases separately exist in the composites of all compositions. The simultaneous existence of ferroelectric and ferrimagnetic properties in the composites is confirmed by measuring their P(E) and σ(B) hysteresis loops and studying the temperature dependences of dielectric and magnetic properties. The synthesized composites have high magnetoelectric characteristics: their voltage coefficient at x = 0.4 is 215 mV/A at a frequency of 1 kHz and 130 V/A at an electromechanical resonance frequency of 380 kHz.     

Influence of Uncertainty of Probabilities of Spontaneous Emission on the Temperature Behavior of the Collisional Self-Broadening Coefficients of Spectral Lines of CO2 Molecules

Optics and Spectroscopy - The influence of deviation of the values of spontaneous emission probability A on the temperature behavior of collisional self-broadening coefficients γ(T) of...     

Thermal stresses in layered barium titanate-based semiconductor ceramics

Thermal stresses emerging in a barium titanate-based semiconducting ceramic during heating by electric current are studied using numerical methods. It is shown that the highest tensile stresses are formed in the plane equidistant from the electrodes. The values of these stresses can be as high as 70 MPa, which is commensurate with the critical stresses. A method is proposed for reducing stresses by developing thermistors with a layered structure.     

Effect of a positive temperature coefficient of resistance in thin films of doped strontium-barium titanate

Thin films of doped semiconducting barium-strontium titanate (Ba,Sr)TiO₃ are prepared by pulsed laser ablation. It is shown that the crystal structure, morphology, and electrical properties of (Ba,Sr)TiO₃ thin films are determined primarily by the actual ablation conditions. The ablation regimes of deposition permitting preparation of uniform polycrystalline thin films with a composition close to that of the target and with grain sizes larger than 0.1 μm are established. These samples have a positive temperature coefficient of resistance in the phase transition region. The change in the resistivity can be as much as 100%.     

Application of Scanning Capacitance Force Microscopy for Detecting Impurity Phases in Ferroelectric Triglycine Sulfate

Technical Physics - An inhomogeneous ferroelectric (triglycine-sulfate (TGS) single crystal with a TGS–TGS+Cr periodic growth impurity structure) has been investigated by scanning capacitance...     

Structure and Magnetic Properties of (Ni1 – xZnx)Fe2O4 Ceramics with a Spatial Change in the Composition

Physics of the Solid State - Samples of homogeneous (x = 0, 0.1, and 0.2) and multilayer ceramics based on solid solutions of nickel–zinc ferrites (Ni1&nbsp;–&nbsp;xZnx)Fe2O4...     

Polarization characteristics of graded thick Ba<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>TiO<Subscript>3</Subscript> films

The barium strontium titanate ceramics Ba_{1 − x} Sr _x TiO₃ with a spatially variable composition has been prepared according to the thick film technology (tape casting). The strontium content over the film thickness is varied from 0 to 30 mol %. The structure and polarization characteristics of the samples prepared have been investigated. It has been found that the polarization characteristics of multilayer structures are determined by the ratio between the thicknesses of layers with different compositions and by their properties. No shift of the hysteresis loops in the graded thick Ba_{1 − x} Sr _x TiO₃ ( _x = 0–0.3) films has been revealed. The results obtained have been analyzed in the framework of modern theoretical approaches.     

Water-soluble ferroelectric crystals with inhomogeneous impurity distribution

Stabilization of the unipolar state via the formation of inhomogeneous impurity distribution in crystal bulk is considered. Possible growth of crystals with stable characteristics is demonstrated on triglycine sulfate (TGS) crystals with a regular inhomogeneous impurity distribution. The properties of TGS crystals with an inhomogeneous distribution of chromium ions grown above and below the Curie temperature T_C are studied. Inhomogeneous TGS crystals of three types are obtained: type-I crystals with a smooth variation of the concentration gradient along the growth direction, type-II crystals with a periodic layer variation of the impurity concentration, and type-III crystals with a sawtooth-like variation of the impurity concentration along the sample length. The TGS crystals with the regular inhomogeneous impurity distribution in the ferroelectric phase are characterized by higher values of the internal bias field E _b , unipolarity coefficient k, and pyroelectric coefficient γ than the inhomogeneous crystals in the paraelectric phase and the crystals with the statistic impurity distribution grown by the conventional method.     

Scanning Capacitance Microscopy of Triglycine Sulfate Crystals with the Profile Chromium Distribution

The spatial capacitance distribution, domain wall configuration, and impurity composition of triglycine sulfate TGS–TGS + Cr crystals with a growth periodic impurity structure have been investigated using scanning capacitance microscopy and X-ray fluorescence and topography. The chromium ion concentration in the strips emerging to the surface has been determined, and the periodic impurity distribution has been established. The difference between the chromium concentrations in nominally pure and impurity strips was found to be ~0.08 wt %, which is reflected in a variation in the capacitance image contrast by 0.17%. It is shown that capacitance images carry information about localization of the impurity gradient regions and domain walls and make it possible to establish a correlation between the defect and domain structures of a ferroelectric crystal.     

Ferroelectric properties of compositionally graded BST ceramics

Homogeneous and graded Ba_{1? x} Sr _x TiO₃ ceramics were produced by thick-film technique (tape casting). In the graded materials, the content of strontium was changed from 0 to 30 mol% in the direction normal to the surface. The microstructure, Ba/Sr spatial distribution, polarization characteristics, and dielectric properties of the samples were investigated. No hysteresis loop offset (neither along E- nor P-axis) in the graded Ba_{1? x} Sr _x TiO₃ structures (x = 0–0.3) was observed. This fact was analyzed on the basis of phenomenological models for graded ferroelectrics. The materials with spatially changing composition were characterized by high-temperature stability of dielectric properties and low temperature coefficient of capacitance.