Synthesis and evaluation of effective parameters in thermal expansion coefficient of Ln(0.6)Sr(0.4)Co(0.2)M(0.8)O(3-delta) (Ln = La,Nd and M = Mn,Fe) perovskite oxide

摘要

In this study, oxides Ln(0.6)Sr(0.4)Co(0.2)M(0.8)O(3-delta) (Ln = La,Nd and M = Mn,Fe) have been prepared and characterized to study the influence of the different cations on thermal expansion coefficient (TEC). TEC decreases favourably with replacement of Nd3+ and Mn3+ ions in the lattice. Nd3+ leads to decreasing ionicity of the Ln-O bond and phase transition from rhombohedral to orthorhombic. Structural parameters of compounds have been determined by X-ray diffraction (XRD). FT-IR analysis has been used to compare the bond strength of different cations in the lattice. Variations of lattice parameters of compounds have been monitored by in-situ XRD at different temperatures in order to study the thermo-chemical expansivity. Concentration of oxide ion vacancy has been determined by high temperature gravimetry. The results show more stability of Mn4+ ions in high temperature in comparison with Fe4+ ions, which suppreses the tendency to lose oxygen from the lattice with the increase in temperature.