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A modified chemical route was utilized to prepare a series of compounds, Ca[Bi.sub.4][Ti.sub.4][O.sub.15] (CBT), Sr[Bi.sub.4][Ti,sub.4][O.sub.15] (SBT), and Ba[Bi.sub.4][Ti.sub.4][O.sub.15] (BBT), belonging to the Aurivillus-type structure with four layers. Detailed studies conducted provide insight into the orthorhombic symmetry, a significant deformation of the perovskite block and the relaxorlike phase transition.

Abstract: We investigated the magnetic and structural properties of TiO2 rutile single- and codoped with Fe and Co prepared by a solid state reaction method. The concentrations of each dopant was varied from 0 to 5%. Most of the samples were ferromagnetic at room temperature. When Co or Fe was single-doped to 3%, only weak room temperature ferromagnetism was observed. But when 1% of Fe or Co was additionally co-doped, magnetic moment per magnetic ion, remnant magnetization, and coercivity were significantly enhanced compared to the single-doped case, and this behavior was observed up to 5% co-doping. The structural study showed the TiO2 rutile phase for all of the samples with second phases of Fe2TiO5 and/or CoTiO3 depending on the contents of Co and Fe, but no indication of Co or Fe metallic cluster was found. The micro composition analysis showed the linear correlation between Co and Fe concentrations, which is a result of enhanced incorporation of magnetic ions into TiO2 host when co-doped. The Mösbauer spectrum showed that the value of the hyperfine field is about 1.5 times as large as that of α-Fe indicating that the Fe impurities substituted into Ti atoms instead of forming iron clusters. [Copyright &y& Elsevier]

Abstract: In this work, we have synthesized polycrystalline SrBi4Ti4O15 (SBiT) ceramics by soft chemical method. These ceramics were structurally characterized by analysis of X-ray diffraction (XRD) patterns, indicates that SBiT ceramics present an orthorhombic structure. Scanning electron micrograph shows that the grains exhibit a plate like morphology. Dielectric relaxations of the SBiT ceramics were investigated in the temperature range 100–700°C. Using the Cole–Cole model, an analysis of the dielectric loss with frequency was performed, assuming a distribution of relaxation time. The presence of the peaks in temperature dependent dielectric loss indicates that the hoping of charge carriers is responsible for the relaxation. Impedance studies shows a non-Debye type relaxation, and relaxation frequency shift to higher side with increase in temperature. A significant shift in impedance loss peaks towards higher frequency side indicates conduction in material and favoring the long range motion of mobile charge carriers. The Nyquist plot shows overlapping semicircles, for grain and grain boundary of SBiT ceramics. The frequency dependent ac conductivity at different temperatures indicates that the conduction process is thermally activated process and the spectra follow the universal power law. The hopping frequency shifts towards higher frequency side with increase of temperature, below which the conductivity is frequency independent. The variation of dc conductivity confirms that the SBiT ceramics exhibits negative temperature coefficient of resistance behavior in high temperature. [Copyright &y& Elsevier]

Abstract: Cerium-substituted bismuth titanate (Bi3.25Ce0.75Ti3O12 (BCT)) films were deposited on the Pt(111)/SiO2/Si(100) substrates by a liquid source misted chemical deposition technique. This film showed X-ray diffraction patterns that crystallization along the (006) direction was suppressed and did not contain any other oxides. The remnant polarization of this film increased with increase in annealing temperature. The 2P r and 2E c values of the BCT film annealed at 700 °C were 19.72 μC/cm2 and 357 kV/cm, respectively. 2P r value of this film decreased by less than 5% of the initial value after 7×109 read/write switching cycles at a frequency of 1 MHz. [Copyright &y& Elsevier]