Role Of Annealing Atmosphere On The Dielectric Properties Of La2NiMnO6

La2NiMnO6 (LNMO) was prepared by gel combustion method from nitrates using glycine as fuel followed by high temperature annealing. The prepared sample was annealed in O-2, air and N-2 and characterized by powder X-ray and neutron diffraction and dielectric measurements. Cation ordered monoclinic (P2(1)/n) and rhombohedral (R-3) phases are observed in the as prepared sample and fraction of monoclinic phase increases on annealing in oxygen atmosphere. On annealing in inert atmosphere decomposition of the sample to manganese rich perovskite, La2NiO4 and NiO is observed. Temperature and frequency dependent permittivity (similar to 10(3)) is observed in the sample annealed in air. The relative permittivity decreases significantly on annealing the sample in oxygen or N-2.atmospher. The formation and annihilation of defects is attributed to the observed large permittivity of La2NiMnO6.