Effect of Ni substitution on the crystal structure and thermal expansion behaviour of (La0.8Sr0.2)0.95MnO3

The effect of Ni doping on (La0.8Sr0.2)0.95MnO3 (LSM) has been studied. Ni substituted lanthanum strontium manganite, (La0.8Sr0.2)0.95Mn1−xNixO3−δ (x = 0 – 1.0) (LSMNix) were synthesized by ceramic route and characterized. Their crystal structure and thermal expansion behaviour have been investigated. It has been shown that the particle size of LSMNix drastically reduces with Ni substitution. The samples calcined at 900 °C indicated orthorhombic symmetry where as those calcined at 1400 °C were shown to be rhombohedral. Compositions up to x = 0.4 indicated single phase while the samples with higher Ni substitution (x ≥ 0.5) showed formation of secondary phases such as La2NiO4 and NiO. The thermal expansion coefficient (TEC) of these samples increased significantly with Ni substitution. The TEC values for LSM and (La0.8Sr0.2)0.95Mn0.5Ni0.5O3−δ were 10.08 × 10− 6 and 14.75 × 10− 6 °C− 1 respectively in the temperature range 25–850 °C.