Extremely small amounts of La and Al doping on the A and B site of BaTiO 3 , respectively, resulting in a solid solution of the type Ba 1-3x La 2x Ti 1-3x Al 4x O 3 have been investigated. The compositions have been prepared by the Pechini process. The x-ray diffraction ͑XRD͒ reveals the presence of tetragonal ͑P4/mmm͒ phase. The XRD data has been analyzed using FULLPROF, a Rietveld refinement package. The compositions have been characterized by dielectric spectroscopy between room temperature and 200°C. The resulting compounds ͑0 ഛ x ഛ 0.008͒ exhibit a remarkable decrease in the Curie temperature as well as a significant enhancement of the dielectric constant.

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Extremely small amounts of codoping La and Ga on the A and B sites of BaTiO 3 , respectively, resulting in a solid solution of the type Ba 1−3x La 2x Ga 4x Ti 1−3x O 3 , have been investigated. The compounds have been prepared by conventional solid-state reaction. The x-ray diffraction ͑XRD͒ shows the presence of the tetragonal ͑P4/mmm͒ phase only. The XRD data have been analyzed using the FULLPROF Rietveld refinement package. The compositions have been characterized by dielectric spectroscopy between room temperature and 200°C. The resulting compounds ͑0 ഛ x ഛ 0.008͒ exhibit a remarkable decrease in Curie temperature as well as a significant enhancement in the dielectric constant.

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In ceria-salt composite systems, the reasons for a two-order enhancement in conductivity relative to that for doped ceria are still unclear. In our attempt to gain further insight in the phenomenon of conduction, we have investigated two different sets of composites: alumina-salt and ceria-salt. Various compositions in the two-phase composite system involving gadolinium-doped ceria (GDC) and alkali carbonates were prepared and characterized. Later, GDC was replaced with alumina, and similar compositions were prepared and characterized to examine the contribution of the GDC phase to the overall conductivity. The conductivity curves, in spite of variations in composition, exhibited a transition at about 500°C, which also corresponds to the melting temperature of the salt phase. From an analysis of the conductivity data, it is observed that at high temperatures, the salt phase plays a significant role in the conduction enhancement. However, at lower temperatures, GDC primarily appears to contribute significantly to the conductivity.