Hydrothermal synthesis of Zn-doped Ni-Mn-AI-O thin films toward high-performance negative temperature coefficient thermistor

摘要

In this study, Zn-doped Ni–Mn–Al–O negative temperature coefficient thermistor (NTC) film with high electrical performance has been demonstrated. XRD, XPS, SEM and electrical measurements were carried out to explore the impact of Zn-doping. The XRD analysis of NiMn~(1.8−x)Al~(0.2)Zn~(x)O~(4)films confirmed the cubic spinel crystal phase regardless of x. The SEM image illustrated that the morphology of NiMn~(1.8−x)Al~(0.2)Zn~(x)O~(4)is closely related to the Zn doping amount. The XPS showed that the relative molar content of Mn_(3+)and Mn_(4+)increased with the increase of Zn doping concentration. Remarkably, the Zn-doped Ni–Mn–Al–O film presented the typical NTC characteristics, and the room temperature resistance (R~(25)) increased with the improvement in Zn doping concentration. Moreover, the thermistor constant B~(25/50)remained reasonably high from 4088 to 4272 K. Meanwhile, the aging test showed that the Zn-doped films were more stable, even aging at 150 °C for 500 h.