A-site Na-doping to enhance room-temperature TCR of La1-xNaxMnO3 polycrystalline ceramics

Abstract

During the exploration on the temperature coefficient of resistance (TCR) of A-site cation-doped perovskites, divalent cation-doped material systems have received increasing attention; however, the TCR performance of monovalent cation-doped perovskites has been less studied. In order to investigate the effect of monovalent Na cation doping on the TCR of La1-xNaxMnO3 (LNMO, x = 0.1, 0.2, 0.3, 0.4, and 0.5) and obtain LNMO materials possessing high TCR values at room temperature, the LNMO perovskite ceramics were synthesized by the Pechini sol–gel method. The effect of sodium cation doping on their structural and electrical properties was investigated by various characterization methods. An increase in Na content affected the grain size and Mn4+ ion concentration in the LNMO ceramics. Furthermore, increasing quantity of Na significantly increased the TCR from 5.89 % K−1 at x = 0.1 to 8.56 % K−1 at x = 0.4. For a Na-doping level x = 0.4, the peak TCR temperature (Tk) at room temperature reached 299.42 K. Among the feasible reasons that could improve the above electrical parameters are the weakened grain boundary scattering, the increase in A-site vacancy, the enhanced double-exchange effects, and the generation of Jahn–Teller distortions. According to the results of this study, the obtained LNMO ceramics seem to be promising for the application in uncooled infrared bolometer technology.