Effect of addition of 5 wt% of PbO on the microstructure and electrical transport properties of La0.7Ca0.3MnO3

This paper is a report of a study of the effect of addition of 5 wt% PbO on the microstructure and electrical transport properties of La0.7Ca0.3MnO3 (LCMO). LCMO showed a two order decrease in resistivity (rho) over the temperature range (300 K - 40 K) while the peak temperature coefficient of resistance (TCR) value of LCMO increased from 3.5 % K-1 to 9% K-1 with 5 wt% PbO addition. Scanning electron microscope (SEM) pictures showed significant difference in the microstructure of LCMO after the addition of 5 wt% PbO. PbO added LCMO was found to have an average grain size (similar to15 mm) larger than that of pure LCMO (similar to5 mm). This is due to the presence of a liquid phase of PbO during sintering. These studies illustrate the effect of the grain boundaries on p and TCR. It also shows that 1) resistivity and TCR can be tuned by addition of PbO and 2) optimum concentration and preparative conditions are necessary to produce compounds suitable for device applications.