Investigation of 1~10 mol% SnO2-doped Bi2O3 as Solid Electrolyte

Various Bi2O3 materials (BSO) doped with SnO2 up to 10 mol% have been synthesized by colloidal process and solid state reactions. The objectives are to study the effect of SnO2 dopant on the electrical conductivity and the stability of the BSO materials in reducing atmosphere. The discrepancies existing between the reported Bi2O3-SnO2 phase diagrams are also investigated. X-ray diffraction (XRD) and differential thermal analyzer (DTA) are used to investigate the phase transition behaviors of the BSO samples. Archimedes’ method, XRD, scanning electron microscope (SEM) observation, 2-probe conductivity measurement and mass loss test are used to study the properties of the samples. A revised Bi2O3-SnO2 phase diagram of 0~10 mol% SnO2 region is proposed. Most of sintered BSO samples consist of α-Bi2O3 and Bi2Sn2O7 phases. While the sintered 1 mol% SnO2-doped Bi2O3 (1BSO) is dense and shows single phase α-Bi2O3. The highest electrical conductivity at the range of 450~700oC were obtained by 1BSO sample, which was 7.74×10-5 S/cm at 600oC and 1.78×10-4 S/cm at 650oC. The most noteworthy advantage of SnO2-dopant is that it stabilizes the Bi2O3 matrix in reducing atmosphere in which the oxygen partial pressure is 10-16 atm (controlled by CO/CO2) at 650oC.