High temperature coefficient of resistivity (TCR) of Nd0.67Sr0.33MnO3 films by optimizing sintering temperature

Abstract

In this study, Nd0.67Sr0.33MnO3 (NSMO) films are deposited on La0.3Sr0.7Al0.65Ta0.35O3 (LSAT) substrates using sol–gel spin coating method and sintered at different temperatures (Ts = 1250, 1300, 1350, 1400 and 1450 °C). Consolidated analysis of their crystal structure, surface morphology and valence states enables one to conclude that increased Ts facilitates grain growth and enhances crystallinity of films. Moreover, enhancing Ts from 1250 to 1350 °C leads to a decrease in Mn-O bond length (d(Mn-O)) and an increase in Mn-O-Mn bond angle (θ(Mn-O-Mn)). In the XPS analysis, the Mn4+ and O2– content kept increasing with the rise of Ts. When Mn4+ concentration ≤ 33%, the double exchange (DE) interactions was undoubtedly facilitated, which was beneficial for the electrical properties of the NSMO films. These changes eventually result in large temperature coefficient of resistivity (TCR). According to these results, Nd0.67Sr0.33MnO3 film, with a maximum TCR value of 21.85% K−1 at Ts = 1350 °C, are promising materials for the manufacturing of sensitivity switches and infrared bolometers.