Effect of ageing on magnetic and electrical properties of Ti–substituted La-Sr manganites

The changes of structural, magnetic and electrical parameters of ceramic La0.8-xSr0.2+xMn1-xTixO3+γ (0.025 ≤ x ≤ 0.150) manganites during long-term storage at room temperature and after thermal cycling were investigated. The unit cell volume (V) of all manganites decreased over time. Most considerable decrease of V and broadening of X-ray diffraction lines width were observed in the samples with high quantity of titanium. During the storage period magnetization (σ) and Curie point (Tc) of manganites with relatively low Ti content decreased, while the compositions with high values of “x” exhibited some trend of σ and Tc increase. The resistance of the samples with x < 0.100 increased over time. Fluctuations of magnetization of all thermal-aged samples were within the error of measurement, and Curie point of manganites with x = 0.150 showed the rise. From the data obtained it might be inferred that ageing phenomena in Ti-substituted manganites can be associated with oxidation processes, the transfer of Ti4+ to vacant sites in rare-earth sublattice and formation of microinhomogeneities