Structural and electrical properties of thick film thermistors based on perovskite La–Mn–Al–O

LaMnO3 thick films doped with Al were fabricated on Al2O3 substrates by screen printing technique. Significantly composition-dependent structural phase transformation and grain size were observed in Al-doped LMO thick films by X-ray diffraction and scanning electron microscopy. The resistivity of all the thick films decreased with the increase of temperature, indicating a negative temperature coefficient effect. Al doping resulted in a sharp rise in room resistivity (ρ0) and thermal constant (B) as compared with non-doped films. Among the films investigated, the film with composition x=0.4 showed a unique electrical property and was further examined in detail using the complex impedance analysis, in order to unveil the structure–property relationship.