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This investigation involves the synthesis and study of dielectric, structural and impedance properties of polycrystalline Bi(Ni 2/5 Ti 2/5 Fe 1/5)O 3 (symbolized as BNTF) nano-ceramic. The BNTF polycrystalline sample was fabricated through the use of a conventional solid-state reaction route. X-ray structural examination reveals that the parent compound (i.e., BiFeO 3) crystallizes in the rhombohedral structure (space group-R3c) while that the BNTF compound crystallizes in orthorhombic symmetry. The substitution of NiTiO 3 into BiFeO 3 enhances various properties and reduces electrical leakage current. The average crystallite size is calculated to be 29 nm. The room temperature textures and surface morphologies of the specimen were verified by field-emission scanning electron microscope, and show uniform grains distribution on sample surfaces. Dielectric parameters (constant and tangent-loss) and impedance spectroscopy parameters of NiTiO 3 modified BiFeO 3 compound were investigated over a wide temperature range (25–500 °C) at different frequency (25 kHz-500 kHz), which offers several interesting features of BNTF material suitable for further device applications. [ABSTRACT FROM AUTHOR]

Dielectric studies were carried out on Nd 2 CuTiO 6 samples prepared by high temperature solid-state reaction followed by annealing under different oxygen partial pressures. X-ray diffraction studies revealed that the orthorhombic (Pnma) structure of Nd 2 CuTiO 6 is retained in all the samples. The room temperature permittivity at 100Hz was found to be about 200 in the air-annealed sample, and it increased considerably to about 3000 upon annealing in argon atmosphere. The electrical conductivity in the argon-annealed compound was found to be an order of magnitude higher than that for the air-annealed sample. On annealing in oxygen, both permittivity and electrical conductivity of the sample were found to be significantly reduced. The variation in dielectric properties could be attributed to the induction or annihilation of mixed valence state of copper and oxygen vacancies, which was supported by X-ray photoelectron and diffuse reflectance spectroscopy data. The analysis of temperature and frequency dependent conductivity and dielectric data showed that the overlapping large polaron tunnelling (OLPT) mechanism is responsible for the observed dielectric relaxations and conduction. The observed systematic dependence of properties on the oxygen partial pressure of the annealing environment suggests a simple method to tune the electrical properties of Nd 2 CuTiO 6. • Annealing conditions affect dielectric properties in rare-earth double perovskite. • Crystalline structure remains unchanged. • Changes in mixed valence of copper and oxygen vacancies. • Dielectric properties may be tuned by varying synthesis conditions. • Conduction due to overlapping large polaron tunnelling. [ABSTRACT FROM AUTHOR]