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An analytical model based on an equivalent capacitance circuit for expressing a static effective permittivity of a composite dielectric with complex-shaped inclusions is presented. The dielectric constant of 0–3 composites is investigated using this model. The geometry of the capacitor containing a composite dielectric is discretized into partial parallel-plate capacitor elements, and the effective permittivity of the composite is obtained from the equivalent capacitance of the structure. First, an individual cell diphasic dielectric (a high-permittivity spherical inclusion enclosed in a lower permittivity parallelepiped) is considered. The capacitance of this cell is modeled as a function of an inclusion radius/volume fraction. The proposed approach is extended over a periodic three-dimensional structure comprised of multiple individual cells. The results of modeling are compared with results obtained using different effective medium theories, including Maxwell Garnett, logarithmic, Bruggeman, series, and parallel mixing rules. It is found that the model predictions are in good agreement with the experimental data. The equivalent capacitance model may be applied to composites containing inclusions of any geometry and size. Although the method presented is at static electric field, it can be easily generalized for prediction of frequency-dependent effective permittivity. [ABSTRACT FROM AUTHOR]

La[sub 0.5]Sr[sub 0.5]Co[sub 1-x]Ni[sub x]O[sub 3-δ] (0≤x≤0.6) ceramics were prepared using a conventional solid-state ceramic route. The thermal properties—thermal conductivity and heat capacity—of these ceramics were measured by the photopyroelectric technique. The thermal conductivity was found to increase with increasing Ni content. These materials were also found to exhibit a metallic-type variation of thermal conductivity with temperature, and no metal-insulator (M-I) transition was found to occur in any of the samples prepared by this route. However, a M-I transition was found to occur in La[sub 0.5]Sr[sub 0.5]CoO[sub 3-δ] samples prepared by hot pressing. The difference is attributed to variations in oxygen content in the samples. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The effect of Nickel doping on La0.5Sr0.5CoO3-delta has been analyzed by measuring the composition dependence of alpha, epsilon, kappa and c (sub p). The thermal conductivity and heat capacity are found to increase with Nickel content.

Optical absorption and emission measurements are reported for the Cs2NaSmCl6 and Cs2NaYCl6:Sm3+ (1 or 30 mol %) systems under variable-temperature (10–298 K) conditions. Twenty-six crystal-field levels spanning 13 multiplets of the Sm3+ 4f 5 electronic configuration are located and assigned on the basis of the experimental data, and these energy level results are rationalized in terms of a nine-parameter 4f-electron Hamiltonian. The most intense electric-dipole vibronic lines observed in the spectra are assigned to one-phonon vibronic transitions associated with the three odd-parity ‘‘moiety’’ modes of the SmCl3-6 octahedral clusters ν3(t1u), ν4(t1u), and ν6(t2u). Intensity calculations are reported for both the no-phonon magnetic-dipole (origin) transitions and the one-phonon (ν3, ν4, and ν6) electric-dipole vibronic transitions. [ABSTRACT FROM AUTHOR]

Optical absorption and emission measurements are reported for the Cs2NaYCl6:Nd3+ (∼5 mol %) system under variable-temperature (4.2–296 K) conditions. The absorption measurements span the 12 000–24 000 cm-1 spectral region, and emission spectra are presented throughout the 13 300–18 860 cm-1 region. All the spectra are consistent with the retention of octahedral (Oh) site symmetry for the Nd3+ ions down to 4.2 K. Thirty-four crystal-field levels spanning 14 multiplets of the Nd3+ 4f3 electronic configuration are located and assigned on the basis of the experimental data. The most intense lines observed in each of the multiplet-to-multiplet transition regions are assigned to one-phonon (electric-dipole) vibronic transitions associated with the three odd-parity moiety modes of the NdCl3-6 cluster, ν3(tlu), ν4(tlu), and ν6(t2u). The ν3 lines generally appear as doublets (split by ∼10–15 cm-1) and are displaced from magnetic-dipole origins by ∼245–260 cm-1; the ν4 lines are displaced from origins by ∼100 cm-1, and are generally sharp and symmetric; and the ν6 lines are generally asymmetric in shape (or appear as doublets split by ∼2–6 cm-1), and are displaced from origins by 70–75 cm-1. Additional vibronic lines are observed persistently at displacement energies of ∼40–45 and ∼55–60 cm-1, but these lines are considerably less intense than those assigned to the ν3, ν4, and ν6 moiety-mode vibrations. The energy level data obtained from experiment is rationalized in terms of a 9-parameter model which includes the radial spin-orbit interaction parameter (ζso), the Slater–Condon one-particle electrostatic interaction parameters (F2, F4, and F6), the two-particle electrostatic configuration-interaction parameters (α, β, and γ), and the octahedral (Oh) crystal-field interaction parameters... [ABSTRACT FROM AUTHOR]

Presents a study which focused on polarization suppression in lead(zirconium, titanium)oxygen[sub3] thin films. Occurrence of optical suppression effect; Methods; Results and discussion.

Focuses on a study which examined photoinduced hysteresis changes and optical storage in (Pb,La)(Zr,Ti))[sub3] thin films and ceramics. Types that thin films and bulk ceramics exhibit in their hystreresis behavior; Cause of the voltage-shift effect; Implication of the thickness dependence of the voltage shift.