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Emission of greenhouse gases in the process of combustion of fossil fuel to generate energy is a major threat to the planet earth due to global warming. The combustion processes also result in a sizeable amount of heat that gets wasted. Our energy demand will continue to increase by 30- 40% by the next 20 years. An eco-friendly technology is the need of the hour to tackle the waste heat expelled into the atmosphere and to keep greenhouse gases under check. Thermoelectricity deals with the conversion of heat into electricity. Being an eco-friendly technique, numerous researches are ongoing in the field of thermoelectric generation to convert the wasted heat into useful electricity. Among wide varieties of thermoelectric materials, oxide thermoelectric materials are advantageous due to its structural and chemical stability at high-temperature region. The current study is based on the enhancement of the electrical conductivity of CaMnO3 perovskite by the trivalent substitution of Sm3+ at the Ca2+ site. A higher valent substitution at the A site of a CaMnO3 will induce Mn3+ ions in the Mn4+ matrix that will lead to a Jahn-Teller distortion and thereby increase the conductivity. A two order increase in the electrical conductivity was observed for Sm0.1Ca0.9MnO3 at 573 K than that of pure CaMnO3. A maximum value of ZT obtained is 0.095 at 1073 K for Sm0.05Ca0.95MnO3, which is higher than the reported values of Lanthanum and Yttrium doped Calcium Manganate. [ABSTRACT FROM AUTHOR]

(K0.5Na0.5)(Nb0.7Ta0.3)O3 (KNNT) thick films were prepared by electrophoretic deposition method on copper plates (substrates). Prior to the deposition, stable suspensions of KNNT powder were prepared in isopropyl alcohol medium with and without adding triethanolamine (TEA) as dispersant. The optical transmittance spectra with time for both the suspensions were recorded and compared. Suspensions with dispersant has shown low transmittance, which indicate that the particles were dispersed very well in isopropyl alcohol. Fourier Transform Infrared (FTIR) spectroscopy was used to analyze the adsorption of TEA on KNNT particles. Suspension with dispersant was used for electrophoretic deposition. The depositions were carried out at various d.c voltages, keeping the deposition duration and inter electrode distance constant. X-Ray diffraction was used for the phase analysis of the films. [ABSTRACT FROM AUTHOR]

The four layered SrBi4Ti4O15 ceramics which belong to the aurivillius family of oxide was prepared by conventional solid state reaction technique. Analysis of the dielectric data as a function of temperature and frequency revealed normal phase transition. The frequency dependent ac conductivity follows Jonscher’s universal power law. Frequency exponent (n), pre-exponential factor (A), bulk dc conductivity (σdc), and hopping frequency (ωp) were determined from the fitting curves. The variation of frequency exponent with temperature indicates that large polaron hopping mechanism up to curie-temperature, then its changes to small polaron hopping. The activation energies were calculated from ac conductivity, bulk dc conductivity and hopping frequency. The activation energies revealed that conductivity had contributions from migrations of oxygen vacancies, bismuth ion vacancies and strontium ion vacancies. [ABSTRACT FROM AUTHOR]

The four layered SrBi4Ti4O15 ceramics which belong to the aurivillius family of oxide was prepared by conventional solid state reaction technique. Analysis of the dielectric data as a function of temperature and frequency revealed normal phase transition. The frequency dependent ac conductivity follows Jonscher’s universal power law. Frequency exponent (n), pre-exponential factor (A), bulk dc conductivity (σdc), and hopping frequency (ωp) were determined from the fitting curves. The variation of frequency exponent with temperature indicates that large polaron hopping mechanism up to curie-temperature, then its changes to small polaron hopping. The activation energies were calculated from ac conductivity, bulk dc conductivity and hopping frequency. The activation energies revealed that conductivity had contributions from migrations of oxygen vacancies, bismuth ion vacancies and strontium ion vacancies. [ABSTRACT FROM AUTHOR]