Affiliation: | aDepartment of Materials Science and Engineering, University of Virginia, Charlottesville, VA 22904, USA bCharles L. Brown, Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA 22904, USA cDepartment of Materials Science and Engineering, Tsinghua University, Beijing 100084, PR China |
Abstract: | We have successfully synthesized submicron LaCaMnO powder (with a nominal composition of La0.67Ca0.33MnO3) and the LaCaMnO–Al2O3 composite powder by a newly invented precursor sintering technique. It is found that the precursor solution containing polyacrylamide and citric acid can facilitate the formation of LaCaMnO powders at a relatively lower sintering temperature because PAM and citric acid form a polymer network in the solution and the metal ions evenly distribute in the precursor solution. The critical sintering temperature was carefully studied based on X-ray diffraction patterns and scanning electron microscopy images. It turns out that a low-temperature sintering results in nano-sized powders with a particle size of 50–100 nm, but a high-temperature sintering leads to larger clusters of 1–3 μm. For the LaCaMnO–alumina composites system, secondary phases appear if the sintering temperature is relatively high (1200 °C). Magnetoresistance of the LaCaMnO wafer made from the obtained LaCaMnO powder has a maximum of 56.7% at 269 K. More appealing is that LaCaMnO–alumina composite powders have a very high MR, 82.5%, even in the same order of the MR of the epitaxial-grown LaCaMnO thin film. Besides, the advantages of the PST method include simple equipment, common chemical compounds and low-cost. |