Structural and electrical behavior of Ba-doped LaGaO₃ composite electrolyte

In the present work, Ba-doped lanthanum gallate (La_1-xBa_xGaO_3-δ with x = 0, 0.05, 0.10, 0.15, 0.20) have been prepared by solid-state reaction method. X-ray diffraction confirms the formation of perovskite structure with orthorhombic symmetry. Furthermore, Ba doping leads to partial stabilization of rhombohedral phase at room temperature. In addition, the grain size of perovskite phase (LaGaO₃) decreased with Ba-dopant. La_0.85Ba_0.15GaO_3-δ exhibits the highest conductivity of the order of 6 × 10^-3 Scm^-1 at 800°C. The rhombohedral phase formation also enhances the ionic conductivity of the composite system. The calculated activation energy for all the doped samples varied from 0.62 to 0.66 eV in the temperature range of 600 to 800°C, which indicates that the conduction behavior is mainly ionic. Coefficient of thermal expansion for La_0.85Ba_0.15GaO_3-δ is 10.8 × 10^-6°C^-1 from 600 to 800°C, which is in the range required for solid oxide fuel cell applications.