Effect of high temperature sintering on the structural and the magnetic properties of La_1.4Ca_1.6Mn₂O₇

We investigate the effect of sintering temperature on the structural and magnetic properties of La_1.4Ca_1.6Mn₂O ₇ double perovskite manganite compound prepared by the sol-gel route. Three sintering temperatures (1273, 1473 and 1673 K) are utilized for the heat treatment. Regardless of the sintering temperature, the tetragonal crystal structure with the I4/mmm space group is stable. However, a reduction in a and an increase in c lattice parameters along with a significant increase in crystallite-size occur on increasing the sintering temperature. This is also accompanied by the growth of grains. Grain-growth and changing crystallite-sizes account for the changes in magnetization, Curie temperature and magnetic entropy-change values. As the sintering temperature increases from 1273 to 1673 K the Curie temperature increases from 225 to 268 K and the magnetic entropy-change increases from 0.58 to 3.1 J kg^-1 K^-1 respectively.