Influence of sintering temperature and oxygen annealing on transport properties of La0.67Ca0.33MnO3

We investigate the influence of sintering temperature and annealing conditions on the transport properties of La0.67Ca0.33MnO3 (LCMO) samples prepared by the solid-state reaction method. In the plot of resistance as a function of temperature, R(T), we observe two peaks for air-annealed samples, which is attributed to the inhomogeneous distribution of oxygen-whereas the sample annealed in oxygen shows only a single peak, which is explained on the basis of homogeneous distribution of oxygen and grain connectivity. The sharpness in the transition peak is described in terms of the temperature coefficient of resistance, which is calculated using R(T) data. We present and compare here the results of structural, transport and magnetic measurements of LCMO prepared at different sintering temperatures as well as under different annealing conditions. The results of the compound are mainly discussed in terms of grain growth and the grain boundaries.