Umaru Ahmadu; Abdulwaliyu B. Usman; Auwal M. Muhammad; Oyeleke I. Olarinoye; Moses Agida
Abstract
Co-doped barium calcium stannate titanate (Ba0.88Ca0.12Ti0.975Sn0.025O3) ceramics, synthesized via solid state reaction and sintered at 1100 °C/3 h. The ceramics were irradiated with thermal neutrons of up to 1.4 × 1010 n/cm2 using a5 Ci Am-Be source having an average flux of 2.7 × 104 ...
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Co-doped barium calcium stannate titanate (Ba0.88Ca0.12Ti0.975Sn0.025O3) ceramics, synthesized via solid state reaction and sintered at 1100 °C/3 h. The ceramics were irradiated with thermal neutrons of up to 1.4 × 1010 n/cm2 using a5 Ci Am-Be source having an average flux of 2.7 × 104 n/cm2.s. Structural analysis of the ceramics indicate a majorly polycrystalline material with a minor secondary phase. The 2θ positions were observed to shift slightly to higher angles and the microstrain remained constant with increase in fluence. The average crystallite size is ∼ 38 nm with anisotropy in lattice expansion observed. Rod-like grains, porous regions and agglomerations were observed in all the specimens. There was general increase in grain size with increase in fluence and the average grain size is∼1 μm. Chemical analysis indicates slight deviation from nominal ones for some irradiated samples. It is concluded that the structural and microstructural changes observed would not affect the performance of the devices based on this material when used in radiation environments of neutrons as the maximum fluence has not exceeded the order of magnitude of threshold for radiation damage. Copyright © 2017 VBRI Press.
Rapaka S C Bose; L Rangaraj; Abanti Nag
Abstract
The p-type thermoelectric material Ca3Co4O9 were synthesized by the sol-gel synthesis in the presence of complexing agent of citric acid and dispersant of polyethylene glycol 400, and followed by the uni-axial hot-pressing (HP) technique. Observation by X-ray diffraction revealed that the formation of ...
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The p-type thermoelectric material Ca3Co4O9 were synthesized by the sol-gel synthesis in the presence of complexing agent of citric acid and dispersant of polyethylene glycol 400, and followed by the uni-axial hot-pressing (HP) technique. Observation by X-ray diffraction revealed that the formation of phase pure sample on calcination at 1073 K for 4 h. Scanning electron microscopy indicated that the significant enhancement of the grain growth through HP technique. The density of the sintered pellets increased with an increase of applied pressure. The electrical resistivity was greatly reduced with an increase of the applied pressure, whereas the Seebeck coefficient was little increased with an increase of the applied pressure. As a result, the pellet treated by the HP technique under the condition of 1098 K, 25 MPa and 30 min showed a maximum power factor of about 498 μWm-1K-2 at 950K. Copyright © 2017 VBRI Press.
