Improved temperature coefficient of resistance in La1-xCaxMnO3:Ag0.2 (0.25 ≤ x≤ 0.33) ceramics prepared by sol–gel method

Abstract

A series of La1−xCaxMnO3:Ag0.2 (0.25 ≤ x ≤ 0.33) polycrystalline ceramic materials were prepared by sol–gel method using methanol as solvent. X-ray diffraction analysis showed that all samples consisted of pure perovskite structurewith no second phase. The grain size and morphology of the samples were studied by scanning electron microscopy. The results showed the samples with good crystallinity, large grain size, and high density. X-ray photoelectron spectroscopy measurement results shows that Ag exists in manganese oxides in two forms (Ag and Ag+). The resistivity temperature curves showed that all samples exhibited a sharp metal–insulator transition. At x = 0.28, the temperature coefficient of resistance was 78.8%·K−1. The magnetization-temperature curves also showed a sharp ferromagnetism–paramagnetism transition, and the Curie temperature increased gradually. These ceramics act as promising candidates for application in infrared and bolometric detectors.