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Dielectric properties of 0.945([Bi.sub.0.5][Na.sub.0.5])Ti[O.sub.3]-0.055BaTi[O.sub.3] (BNBT5.5) ceramics are analyzed. The studies have shown that BNBT5.5 is a relaxor with a characteristic relaxation time that follows Vogel-Fulcher's law and the Vogel-Fulcher parameters of the relaxation time are calculated.

A freezing casting technique is used for constructing ceramic-polymer composites in which the 2 phases are arranged in an electrically parallel configuration. The finished barium-titanate-polymer composites have displayed the high dielectric constant (1000) of ferroelectric ceramics while maintaining the unique properties of polymer materials such as graceful failure, low dielectric loss and high dielectric breakdown.

The strain coupling, microstructural evolution, and functional properties of a series of BaTi[O.sub.3] (BTO) films with different second-phase oxide additions, Ti[O.sub.2], MgO, Zr[O.sub.2], [Sm.sub.2][O.sub.3] and [Y.sub.2][O.sub.3] (YO), is studied. The studies have shown that the strain state in BTO is tuned by different additions and compared with BFO, which is switched from tensile for a pure film on STO to compressive by the presence of the second phase (SmO).

The synthesis, as well as the electrical properties of Mn[Co.sub.3]-added 74([Bi.sub.1/2][Na.sub.1/2])Ti[O.sub.3]-20.8([Bi.sub.1/2][K.sub.1/2])Ti[O.sub.3]-5.2BaTi[O.sub.3] lead-free piezoelectric ceramics are discussed. The impact of Mn doping on the different electrical properties of the ceramics is also analyzed.

The precipitation of barium or strontium carbonates in alkaline silica-rich environments leads to crystalline aggregates that have been named silica/carbonate biomorphs because their morphology resembles that of primitive organisms. These aggregates are self-assembled materials of purely inorganic origin, with an amorphous phase of silica intimately intertwined with a carbonate nanocrystalline phase. We propose a mechanism that explains all the morphologies described for biomorphs. Chemically coupled coprecipitation of carbonate and silica leads to fibrillation of the growing front and to laminar structures that experience curling at their growing rim. These curls propagate in a surflike way along the rim of the laminae. We show that all observed morphologies with smoothly varying positive or negative Gaussian curvatures can be explained by the combined growth of counterpropagating cuds and growing laminae.

Series of polycrystalline samples of Z[n.sub.2-x] C[u.sub.x] Ba F[e.sub.16] [O.sub.27] were prepared by usual ceramic methods, where (x=0.0, 0.4, 0.6, 0.8, 1.0, 1.4). X-ray analysis were obtained at room temperature using Co[[k.sub.[alpha]] with [lambda] = 1.790[A.sup.0] confirmed the presence of W-type hexaferrite phase structure . Saturation magnetization and hysteresis loops curves measurements at room temperature were studied as a function of C[u.sup.2+] substitution. It can be seen that the C[u.sup.2+] content slightly decreases the saturation magnetization from 25 to 20 (emu[g.sup.-1]), all hysterysis loops are closed which indicates low anisotropy field and low saturation magnetization field. The dc conductivity and thermoelectric power was measured in range from room temperature up to T = 750 K for all samples. The thermoelectric power decreases by increasing C[u.sup.2+] content and the conductivity increases with temperature. The value of the charge carrier concentration increases by increasing temperature and C[u.sup.2+] content . Magnetic properties, Electrical properties, charge carrier concentration X-ray analysis, Hexagonal ferrite, INTRODUCTION Hexaferrite powder with a narrow size distribution are promising materials for industrial applications due to their high coercivities and their moderate saturation magnetization (1), (4). Polycrystalline hexaferrite are very [...]

A specific polarized Raman procedure is developed for the quantitative characterization of local biaxial domain texture in polycrystalline BaTi[O.sub.3] (BT) by considering the angular distribution. The angular dependence of Raman intensity measured in polycrystalline BT has depended on the statistical distribution of domain angles in the laser microprobe.

The preparation of hierarchical dendrites of BaMo[O.sub.4] by a similar method at room temperature in an ultrashort reaction time, as well as the observation of shape evolution from dendrites to rods and further to particles with different aging times is described. The findings revealed that the formation of the 3-D structures was strongly dependent on the composition of the microemulsion and at prolonged aging time, the dendrites evolved into rods and further into particles, driven by the lattice distortion energy required to evolve the crystal from a metastable to a stable state.

Using quantum mechanics (QM, Density Functional Theory) we show that all four phases of barium titanate (BaTi[O.sub.3]) have local Ti distortions toward (an octahedral face). The stable rhombohedral phase has all distortions in phase (ferroelectric, FE), whereas higher temperature phases have antiferroelectric coupling (AFE) in one, two, or three dimensions (orthorhombic, tetragonal, cubic). This FE--AFE model from QM explains such puzzling aspects of these systems as the allowed Raman excitation observed for the cubic phase, the distortions toward observed in the cubic phase using x-ray fine structure, the small transition entropies, the heavily damped soft phonon modes, and the strong diffuse x-ray scattering in all but the rhombohedral phase. In addition, we expect to see additional weak Bragg peaks at the face centers of the reciprocal lattice for the cubic phase. Similar FE--AFE descriptions are expected to occur for other FE materials. Accounting for this FE--AFE nature of these phases is expected to be important in accurately simulating the domain wall structures, energetics, and dynamics, which in turn may lead to the design of improved materials. barium titanate | phase transition

The structural and morphological features of Ba{[NO.sub.3]}[.sub.2] as well as the formation of BaO from Ba{[NO.sub.3]}[.sub.2] during the thermal release of [NO.sub.x] was investigated by choosing a model system of Ba{[NO.sub.3]}[.sub.2] supported on [alpha]-[Al.sub.2][O.sub.3]. At high temperature annealing, the single crystal Ba{[NO.sub.3]}[.sub.2] particles decompose to form multiple BaO particles, clustered together to maintain morphology of the parent Ba{[NO.sub.3]}[.sub.2].

Ba(sub 8)Ga(sub 16)Si(sub x)Ge(30-x) were synthesized and their structural and electrical properties compared to those of similar type-I clathrates (Ba(sub 8)Ga(sub 16)Si(sub x)Ge(30-x)and Sr(sub 8)Ga(sub 16)Si(sub x)Ge(30-x)). The increasing Si content is accompanied by a slight increase in the absolute Seeback coefficient even as the carrier concentration increases and the resistivity decreases.

The effect of Ti and Mg dopants on the structural properties and band-gap energies of Ba(sub 0.5)Sr(sub 0.5)TiO3 (BST) thin films grown on LaAlO3 substrates are investigated. The transmission spectra of these BST thin films measured by ultraviolet-visible spectrophotometer show that the band-gap energies are strongly dependent on the dopant concentration.

The synthesis of iminobis(methylphosphonic acid) (H(sub 2)O(sub 3)PCH(sub 2))(sub 2)NH as a starting materialwas made to obtain barium bisphosphonate [Ba(sub 3)(C(sub 3)PCH(sub 2)NH(sub 2)CH(sub 2)PO(sub 3) as a pure metal. The barium bisphosphonate is an example of microporus inorganic-organic hybrid materials built up from flexible linkers.

Raman spectroscopy of the two phases that is Ba(Sub7.5)Al(sub 13)Si(sub29) and Eu(sub 0.27)Ba(sub 7.22)Al(sub 13)Si(Sub 29) and the magnetic properties of the phases are presented. It is found that Raman spectra are consistent with both the phases having minimal guest-host interactions and susceptibility data for Eu(sub 0.27)Ba(sub 7.22)Al(sub 13)Si(Sub 29) imply weak magnetic ordering and indicate a 2+ oxidation state for the Eu ion

The crystal chemistry and magnetic properties of polycrystalline Ba(Sub 3)MRuIrO(sub 9) (M(super 1+) = Li, Na; M(super 2+) = Mg, Ni, Zn; M(super 3+) = Bi, In) are investigated. It is found that there are antiferromagnetic interactions within the phase sharing octahedra that contain a disordered mixure of Ru and Ir on a single crystallographic site.

The crystal chemistry and magnetic properties of mixed ruthenium-iridium triple-perovskite series Ba(sub 3)MRuIrO(sub 9) (M = Y, lanthanides) is described. It is found that Ba(sub 3)Ln(super 3+)RuIrO(sub 9) compounds have less weiss constants, low effective magnetic moments at low temperatures, consistent with antiferromagnetic correlation.

BaZnOS exhibits a structure composed of corner-linked ZnO2S2 tetrahedra, which represents a new coordination environment for zinc in the solid state. Measurement and calculation of the electronic structure shows a band gap of 3.9(3) eV, larger than the corresponding values in ZnS and ZnO and consistent with the more ionic nature of BaZnOS.

A study is conducted on a 160-nm-thick (Hg0.9Re0.1)Ba2CaCu2Oy [(Hg,Re0-1212] epitaxial thin films that were fabricated on 2degree-18.4degree -tilt SrTiO3 vicinal substrates with thin buffer layers. The studies indicate that the vicinal films had superior crystallinity and superconducting properties comparable to those for conventional films with no tilt.

Metal nanocomposite thin films formed by nanometer-sized gold particles embedded in BaTiO3 matrices (Au:BaTiO3) were fabricated on MgO (100) and glass substrates using a pulsed-laser deposition technique. A sign reversal was demonstrated in the nonlinear absorption coefficient (beta) and nonlinear refractive index (n2) of Au:BaTiO3 films with same Au concentration but a different nanostructure.

The microstructure and electrical properties of ultrathin BaTiO3 films (2-7 nm thick) have been discussed. The leakage current, switching time, and fatigue characteristics of the films are also discussed.

In the study conducted, YBCO films of 0.2 micrometre and 0.8 micrometer thickness are prepared by post-annealing of the precursor films deposited from Y, BaF2 and Cu sources at room temperature is discussed. However according to the TEM observation of several films prepared using different annealing conditions, it is found that the oxygen flow rate appears to affect the thickness of the epitaxial YBCO layer.

The electrical and magnetic tunabilities of high quality bilayer films of Ba[Fe.sub.12][O.sub.19] (BaM)/[Ba.sub.0.5][Sr.sub.0.5]Ti[O.sub.3] (BST), which is grown on a A-oriented sapphire substrates by using pulsed laser deposition (PLD), are examined. Magnetic hysteresis loops have indicated that large magnetic anisotropy between the in-plane and out-of-plane field orientations and the M-H characteristics of BaM are affected by the presence of the BST layer.

The effects of postannealing temperature and dopant concentration on microstructure and electrical properties of the holmium-doped 200-nm-thick BaTiO3 (BT) thin films prepared by rf magnetron sputtering are investigated. The results show that adding Ho2O3 as the acceptor dopant increases the dielectric constant and reduces the leakage current density of BaTiO3 films.

The article presents a newly devised approach, which can be used for the selective pure-phase synthesis of the multiferroic Ba[MF.sub.4] (M = Mg, Mn, Co, Ni, and Zn) family. The approach is shown to be extremely beneficial for the production of pure and polycrystalline Ba[F.sub.4]

The article presents a new surface-layer model, which is employed to explain the properties and axial polarization distributions taking place in the ferroelectric nanowires with different surface compositions. The various effects of the different surface compositions on the properties of the nanowires are also described.

Positron annihilation and Raman spectroscopies are used for studying the defect properties of perovskite type materials ([Ba.sub.3]B' [Nb.sub.2][O.sub.9] (where B' = Mg, Zn, or Co)) with near-stichiometric compositions. The existence of an internal electric field between charged 1:1 nanoregions and the rest of material has created conditions for preferential positron annihilation that affect the obtained positron lifetime values.

Combinatorial pulsed deposition (PLD) is used for the epitaxial growth of [Ba.sub.0.6][Sr.sub.0.4][Ti.sub.1-x][Zr.sub.x][O.sub.3] composition spread thin film library on SrRu[O.sub.3]/SrTi[O.sub.3] layer by combinatorial pulsed deposition (PLD). Statistical and temperature-related capacitive measurements across the library have displayed variations in the dielectric properties and have identified doping windows with enhanced permittivity and tunability.

A modified eight-order Landau potential is described for the BaTi[O.sub.3] single crystal by considering the quantum mechanical effects at low temperature. The new Landau potential is used for calculating the dielectric coefficients, spontaneous polarizations, temperature-electric field phase diagram and piezoelectric coefficients.

Pb[([Zr.sub.0.52][Ti.sub.0.48]).sub.0.96][Nb.sub.0.04][O.sub.3] (PZTN) thin films are deposited on BaPb[O.sub.3] (BPO) electrodes of different thicknesses by rf-magnetron sputtering. The studies have shown that the tensile stress in the films have originated from the phase transformation stresses and the ferroelectric and dielectrics properties are improved with the raise of tensile stresses.

The thickness dependence of critical current density ([J.sub.c]) is examined in Y[Ba.sub.2][Cu.sub.3][O.sub.7-x] films with BaZr[O.sub.3] (BZO) nanorods (YBCO/BZO) aligned along the film normal. The results have shown that the thickness dependence of [J.sub.c] is dictated by the microstructure and hence pinning mechanism in YBCO films.

Several studies are conducted to analyzed the impact of the size and number of the BaZr[O.sub.3] nanorods on the flux pinning properties and microstructure of the Sm[Ba.sub.2][Cu.sub.3][O.sub.y] thin films. The diameter of the BZO nanorods is shown to decrease with a decrease in the substrate temperature.

Barium titanate (BT) and montmorillonite (MMT) nanoparticle are covalently-bonded by organically modifying the particle surfaces and by chemically reacting them in solution. The thermodynamic properties of the glass transition process, the macroscopic mechanical properties of the nanocomposites and the dynamics of the polymer segments at the inorganic interfaces have shown that the filler configuration has increased the polymer-ceramic interfaces.

Epoxy resin composites based on organically modified montmorillonite (oMMT) or barium titanate (BT) (BaTi[O.sub.3]) nanoparticles are examined in order to delineate the effects of the high aspect ratio of the MMT and the high permittivity of the BT particles. The effect of the decreased glass transition, interfacial area, polymer-phase at the organic-inorganic interface and of the dielectric breakdown on the electrical energy storage capabilities of these composites is examined.

The temperature and field dependence of the I-V characteristics of [Ba.sub.0.8][Sr.sub.0.2]Ti[O.sub.3] thin films and [Ba.sub.0.8][Sr.sub.0.2]Ti[O.sub.3]/Zr[O.sub.2] multilayer thin films on Pt/Ti/Si[O.sub.2]/Si substrates are analyzed. Leakage current behaviors of the film are studied and the bulk limited Poole-Frenkel mechanism has dominated the leakage current in the high field region.

Impedance spectroscopy methods are used for analyzing the physical model in a two-phase system toward determining of dielectric constant of dielectric particles suspended in liquids at various solids loading levels. The parameters obtained from fitting are compared with the data obtained from simulations of brick layer models and Maxwell-Wagner effective media model.

[Ba.sub.0.6][Sr.sub.0.4]Ti[O.sub.3]/[Ni.sub.0.8][Zn.sub.0.2][Fe.sub.2][O.sub.4] (BST/NZO) composites are prepared by the conventional solid-state reaction method. The giant dielectric behavior of the BST/NZO composites is ascribed to the Maxwell-Wagner polarization.