Thesis (M.Sc.)--Chulalongkorn University, 2009

(BYZ) pellets with x=0.06-0.4 were fabricated by solid state reactions with a relative density higher than 95\%. The microstructures of the BYZ pellets reveal that BYZ surface has higher porosity than that of bulk, which may arise from the BaO evaporation during sintering process. The impedance analysis shows that the higher values of the bulk conductivity than those of the grain boundary. The highest bulk proton conductivity is obtained at x=0.1, while the highest grain boundary and total proton conductivity is at x=0.2. The activation energies of the proton conductivity are between 0.42-0.47 eV and 0.68-0.82 eV in the bulk and grain boundary, respectively. The dense and uniform BYZ thin films of 140-200 nm in thickness were obtained by co-sputtering (M1) and 2-step sputtering (M2) techniques. The XRD patterns of M1-BYZ thin films show that the concentration of Y is increased with the increasing DC power of the Y target. phase segregation is observed in the M1-BYZ files, while the YSZ phase segregation appears in the M2-BYZ thin films. The conductivities of the BYZ thin films are about 100 times than those of the pellet samples. This high conductivity may be caused by microstructure, grain size, impedance measurement, impurities, and ionic conduction mechanism.