• P R S Warriar

      Articles written in Bulletin of Materials Science

    • Superconducting YBa2Cu3O7–𝛿 thick film (𝑇c (0)$ = 92 K) on a newly developed perovskite ceramic substrate

      S U K Nair P R S Warriar J Koshy

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      A complex perovskite oxide, YbBa2NbO6, as a non-reacting substrate for YBa2Cu3O7–𝛿 superconducting film has been developed. The dielectric constant and loss factor values of the material are in the range suitable for its use as substrate for microwave application. A YBa2Cu3O7–𝛿 superconducting thick film dip coated on YbBa2NbO6 substrate gave a 𝑇c (0) of 92 K and current density of ∼ 1.3 × 104 A cm-2.

    • Ba2ErNbO6: A new perovskite ceramic substrate for Bi(2223) superconducting thick films (𝑇c(0) = 110 K)

      S U K Nair P R S Warriar J Koshy

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      Barium erbium niobate (Ba2ErNbO6) has been developed as a new substrate for (Bi,Pb)2Sr2Ca2Cu3O𝑥 [Bi(2223)] superconductor film. Ba2ErNbO6 (BENO) has a cubic perovskite structure with lattice constant, 𝑎 = 8.318 Å. The Bi(2223) superconductor does not show any detectable chemical reaction with BENO even under extreme processing conditions. Dip coated Bi (2223) thick film, Ba2ErNbO6 substrate, gave a 𝑇c (0) of 110 K and current density of ∼ 4 × 103 A cm-2 at 77 K and zero magnetic field.

    • Synthesis, characterization, sintering and dielectric properties of nanostructured perovskite-type oxide, Ba2GdSbO6

      C Vijayakumar H Padma Kumar Sam Solomon J K Thomas P R S Warriar J Koshy

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      Nanoparticles of barium gadolinium antimonate (Ba2GdSbO6), a complex perovskite-type oxide, has been synthesized using an auto ignition combustion process for the first time. The nanoparticles thus obtained have been characterized by powder X-ray diffraction, thermogravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy and transmission electron microscopy. The XRD studies have shown that the as-prepared powder is phase pure Ba2GdSbO6 and has a complex cubic perovskite (A2BB′O6) crystalline structure with lattice constant, 𝑎 = 8.449 Å. The TEM image reveals that the particle size of the as-prepared nano powder was in the range 30–60 nm. The nanocrystals of Ba2GdSbO6 synthesized by the combustion technique could be sintered to 96% of the theoretical density by heating at a temperature of 1560°C for a short duration of 3 h. The surface morphology of the sintered pellet has been studied by scanning electron microscope (SEM). The dielectric constant ($\varepsilon_{r}$) was 20 and the loss factor (tan𝛿) was 0.03 at 3 MHz. By the present combustion technique a phase pure nanopowder of Ba2GdSbO6 could be obtained by a single step process without the need of any calcination step.

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