Narrow Results

A number of compounds in the ${\mathrm{\text{Ca}}}_{4+x}{\mathrm{\text{La}}}_{2-x}{\mathrm{\text{Ti}}}_{5-x}{\mathrm{\text{Nb}}}_x{\mathrm{\text{O}}}_{17}$ (x = 0–2) series were prepared through a mixed oxide solid-state sintering route. These compounds crystallized into orthorhombic (Pbnm) structure. The relative permittivity $({𝜀}_r)$ and temperature coefficient of resonance frequency $({\tau }_f)$ depended on the polarizability of constituent cations while the quality factor $(Q\times f_o)$ was affected by ordering of cations. These compounds exhibited promising ${𝜀}_r$ (74–90) and $Q\times f_o$ (10208–14116 GHz); however, the observed high ${\tau }_f$ (157–542 ppm/${}^{\circ }$C) requires further investigations to tune it through zero.

The complex perovskite Ba₂YbZrO_5.5 has been successfully synthesized as nanoparticles through a single step combustion process for the first time. The X-ray diffraction analysis revealed that the combustion product is phase-pure and has an ordered cubic perovskite structure. Transmission electron microscopy results indicated that the particle sizes are 10–20 nm. The selected area electron diffraction pattern has shown that as-prepared powder is polycrystalline in nature. The UV–visible spectrum analysis confirmed that the optical absorption edge of Ba₂YbZrO_5.5 is around 340 nm, corresponding to a band gap of ~ 3.65 eV. Photocatalytic activity of Ba₂YbZrO_5.5 nanoparticles is investigated for the degradation of methyl orange under solar irradiation.

This paper describes a detailed analysis of the dependence of Raman scattering intensity on the polarization of the incident and inelastically scattered light in PbSc_0.5Nb_0.5O₃ (PSN) single crystals and epitaxially compressed thin films grown on (100)-oriented MgO substrates. It is found that there are significant differences between the properties of the crystals and films, and that these differences can be attributed to the anticipated structural differences between these two forms of the same material. In particular, the scattering characteristics of the oxygen octahedra breathing mode near 810 cm^-1 indicate a ferroelectric state for the crystals and a relaxor state for the films, which is consistent with the dielectric behaviors of these materials.