Tóm tắt

Based on the formula of BaBi0⋅92Cu0⋅08O3, Cu-modified Ba–Bi–O-based perovskite-like negative temperaturerncoefficient (NTC) thermistor thin films were successfully prepared by radio frequency (RF) magnetron sputteringrnmethod with the various deposition temperatures (25 ◦C, 100 ◦C, 200 ◦C and 250 ◦C). The effects of the substraterntemperatures on the phase structures and electrical properties were respectively characterized and investigatedrnby X-ray diffraction (XRD), resistance-temperature measurement, and complex impedance analysis for thernBa–Bi–O-based thin films. Additionally, the cross-sectional microstructures and grain morphologies of thernBaBi0⋅92Cu0⋅08O3 thin films were analyzed by scanning electron microscope (SEM) and atomic force microscopern(AFM). The XRD patterns results showed that the perovskite monoclinic structure with a small amount ofrnBaBiO2.5 s phase could be obtained for the BaBiO3 thin film deposited at 200 ◦C, and also, the main crystallinernphase was transferred from BaBiO2.82 to BaBiO2.5 when the BaBi0⋅92Cu0⋅08O3 thin films were deposited at 200 ◦Crnand 250 ◦C, respectively. Temperature dependent complex impedance spectroscopy was carried out to makernclear the resistance contribution of grain (Rg), grain boundary (Rgb) and contact (Rs) response for the conductionrnmechanisms in the Ba–Bi–O-based thin film deposited at a given substrate temperature. Compared with thernelectrical properties of the BaBiO3 thin film deposited at 200 ◦C such as the room-temperature resistivity (ρ25 ~rn1548 Ω cm) and the thermistor constant (B25/85–3245 K), the better NTC characteristics of a lower ρ25 value ofrnabout 956 Ω cm and a higher B value of approximately 3480 K were found in the BaBi0⋅92Cu0⋅08O3 thin filmrndeposited at a same temperature (200 ◦C). It is believed that the phase structures and electrical properties of thernBaBiO3 perovskite-type NTC thermistor thin films could be adjusted and optimized by a trace amounts of Cu-ionsrnsubstitutions and depositing at an appropriate substrate temperature, which also showed that such as these novelrnBaBiO3-based thin films are feasible with the extensive of actual applications for the NTC thermistors.