Electrical conductivity studies on LAMOX based electrolyte materials for solid oxide fuel cells

In this study, the electrical conductivity of the LAMOX based electrolytes (La1.8Dy0.2Mo2-xWxO9 (x = 0, 0.1, 0.2, 0.5, and 1), and La1.8Dy0.2Mo2-xGaxO9 (x = 0.1)) synthesized by the citrate complexion method has been studied using DC four-probe method. The electrical conductivity of the electrolytes is measured in the temperature range of 800-400 degrees C in the air (similar to 100 ml min(-1)). The effect of W and Ga substitution at the Mo site on the electrical conductivity is evaluated. The long-term electrical conductivity stability test (time on stream) (5 h) is conducted at 650, 580, and 520 degrees C to study the effect of possible phase transition on electrical conductivity. A high-temperature XRD study is also conducted in the temperature range of 500-650 degrees C (during heating and cooling) on selected electrolyte materials (La1.8Dy0.2Mo2-xWxO9 (x = 0 and 0.1) and La(1.8)Dy(0.2)Mo(2-x)G(ax)O(9) (x = 0.1)) to study the alpha <->beta phase transition. The electrical conductivity of these electrolytes in the air at 800 degrees C is in the range of 5.3 x 10(-2) - 14 x 10(-2) S cm(-1). The activation energy (E-A) of these electrolytes is in the range of 1.11-1.62 eV. The VTF parameters sigma(o), B, and T-o are in the range of 67.46-395.88 S cm(-1) K-0.5, 0.122-0.254 eV, and 247-347 degrees C, respectively. The La1.8Dy0.2Mo2-xWxO9 (x = 0.1) shows highest electrical conductivity (14 x 10(-2) S cm(-1), E-A = 1.54 eV) among all electrolytes in air at 800 degrees C and for this material the VTF parameters sigma(o), B, and T-o are 170.32 S cm(-1) K-0.5, 0.153 eV, and 302 degrees C, respectively.