The slope of (λ-λ0/λ0) vs T (Fig. ), where λ and λ0 are the cubic roots of the volume at a particular temperature and room temperature respectively were used to calculate thermal expansion coefficients. The calculated values of the TEC were found to be 13.0 × 10 -6 ˚C-1 for L1P3N3; 13.2 × 10 -6 ˚C-1 for L2P2N3 and 13.4 × 10 -6 ˚C-1 for L3P1N3, of the same order of magnitude as those of the other components of SOFCs, and therefore compatible with commonly used electrolytes such as Y2O3-stabilised ZrO2 (YSZ), Ce0.8Gd0.2O2-δ (CGO) and La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) . These results, however, vary slightly from the value, 10 x 10 -6 ˚C-1 , calculated from XRD measurements and reported by Vaibhav et al. for P4N3 composition . It could possibly of different La:Pr ratio and the fact that they measured the TEC from room temperature to 1000˚C while the results reported here were measured over the temperature range of RT to 800˚C for L1P3N3 and L3P1N3 compositions and RT to 600˚C for L2P2N3 composition.