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    Fabrication and characterisation of boron doped barium stabilised bismuth cobalt oxide nanocrystalline ceramic composite
    (TAYLOR & FRANCIS LTD, 2013) Uslu, İbrahim; Çınar, Emre; Koçyiğit, Serhat; Aytimur, Arda; Akdemir, Ahmet
    In this paper, the fabrication and characterisation processes of both boron doped and undoped barium stabilised bismuth cobalt oxide nanocrystalline ceramic powders using polymeric precursor were reported. Obtained boron doped barium stabilised bismuth cobalt oxide nanocrystalline ceramic powders, which have been synthesised by polymeric precursor technique at temperatures below 900 degrees C and at atmospheric condition, were characterised by X-ray diffraction, Fourier transform infrared and scanning electron microscopy techniques. According to X-ray results, fcc and bcc phases coexist in the samples of the nanocrystalline ceramic powders. Crystallite sizes for body centred cubic structure were calculated using Scherrer equation for both boron doped and undoped samples. In addition, lattice parameters were calculated for all samples.
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    Thermoelectric Properties of Nickel and Boron Co-Substituted NaCo2O4 Prepared by Electrospinning Technique
    (TRANS TECH PUBLICATIONS LTD, 2018) Erdal, Mehmet Okan; Koyuncu, Mustafa; Aksu, Mehmet Levent; Uslu, Ibrahim; Koçyiğit, Serhat
    In this study nickel and boron doped sodium cobalt oxide NaCo2-xNixByO4 (0 <= x <= 0.3, 0 <= y <= 0.1) nanocrystalline thermoelectric ceramic powders were synthesized using electrospinning techniques and then consolidated into bulk ceramics. The differences in the microstructure and thermoelectric properties of the samples as a result of doping effect have been investigated. The crystalline structures of the powders and nanofibers were characterized using Xray diffraction and scanning electron microscopy and BET Analysis before and after the calcination process at different temperatures. Nanofibers prepared by the use of electrospinning technique, have a diameter of approximately 300 nm, and the diameter of the grains of calcined powders was observed to range between 150 to 500 nanometers. Thermoelectric properties of the bulk ceramics were measured by physical properties measurement system (Lot-Oriel PPMS) in a temperature range of 15-300 K. The calculated values of dimensionless figure of merit at 300 K are 4.25 x 10(-5), 5.3 x 10(-6), 8.6 x 10(-5) and 9 x 10(-6) for sintered powders from undoped, Ni and B doped powders, respectively.