Abstract
Two phase samples containing ∼70 vol.% Ga2O3 and ∼30 vol.% yttria-stabilized zirconia (YSZ) were fabricated by sintering powder compacts in air at 1500°C for 1 h and at 1600°C for 1 h and 3 h. Single phase samples of Ga2O3 were fabricated by sintering at 1500°C for 1 h. Sintered samples were packed in Na-β″-alumina powder of composition ∼8.85 wt% Na2O, 0.75 wt% Li2O and 90.4 wt% Al2O3, and were heat treated at 1250°C for up to 20 h. The two phase Ga2O3 + YSZ samples converted into a sodium zirconium gallate of composition Na0.7Ga4.7Zr0.3O8 and balance yttria-stabilized zirconia. The reaction of single phase Ga2O3 was limited to a thin surface layer in which Na-β″-gallate formed. Rapid conversion of Ga2O3 + YSZ samples into Na0.7Ga4.7Zr0.3O8 + YSZ occurred by coupled diffusion of O2− ions through YSZ and of Na+ ions through the formed Na0.7Ga4.7Zr0.3O8, similar to the conversion of α-Al2O3 + YSZ into Na-β″-alumina + YSZ. The phase Na0.7Ga4.7Zr0.3O8 is isostructural with Na0.7Ga4.7Ti0.3O8 which is a one dimensional sodium ion conductor. The conductivity of two phase Na0.7Ga4.7Zr0.3O8 + YSZ composite was measured by Electrochemical Impedance Spectroscopy.
Published Version
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