• R Jose

      Articles written in Bulletin of Materials Science

    • Combustion synthesis and characterization of Ba2NdSbO6 nanocrystals

      V T Kavitha R Jose S Ramakrishna P R S Wariar J Koshy

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      Nanocrystalline Ba2NdSbO6, a complex cubic perovskite metal oxide, powders were synthesized by a self-sustained combustion method employing citric acid. The product was characterized by X-ray diffraction, differential thermal analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy, transmission electron microscopy and scanning electron microscopy. The as-prepared powders were single phase Ba2NdSbO6 and a mixture of polycrystalline spheroidal particles and single crystalline nanorods. The Ba2NdSbO6 sample sintered at 1500°C for 4 h has high density (∼ 95% of theoretical density). Sintered nanocrystalline Ba2NdSbO6 had a dielectric constant of ∼ 21; and dielectric loss = 8 × 10-3 at 5 MHz.

    • Development, characterization, sintering, dielectric and optical properties of NdBa2ZrO5.5 nanocrystals

      V Ratheesh Kumar P R S Wariar R Pazhani J K Thomas R Jose J Koshy

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      Nanocrystalline NdBa2ZrO5.5 has been successfully synthesized through a single step auto-ignition combustion route for the first time. X-ray diffraction and Fourier transform infrared spectroscopy revealed that the combustion product is phase pure and has an ordered cubic perovskite structure. The phase transitions and thermal stability of the nanopowder were investigated by differential thermal and thermogravimetric analyses. Transmission electron microscopy results indicated that the particle sizes are 20–30 nm. Selected area electron diffraction pattern has shown that as-prepared powder is polycrystalline in nature. The optical absorption spectra analysis confirmed that the material falls to the semiconducting range with a bandgap of ∼3.69 eV and therefore, could be used as transparent wide bandgap semiconductor. The relative density of the sintered sample is ∼96% at 1510 °C for 2 h. The surface morphology of the sintered pellet has been studied by scanning electron microscopy and the average grain size observed is ∼0.7 𝜇m. Dielectric constant (𝜀r) of NdBa2ZrO5.5 at 5 MHz is 29.6 and loss factor (tan 𝛿) is 4 × 10-2 at room temperature.

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