Structural and electrical properties of monovalent K doping in Pr0.6(Sr1-xKx)0.4MnO3 polycrystalline ceramics

Pr_0.6(Sr_1-xK_x)_0.4MnO₃ polycrystalline ceramics (PSKMO, 0 ≤ x ≤ 0.25) were fabricated via using sol–gel method. The structure of PSKMO ceramics was identified to be the orthorhombic structure with Pnma space group. As K-concentration (x) rose, grain sizes increased significantly. The constituent elements of PSKMO ceramics were uniformly distributed on the surface. From the resistivity dependence of temperature (ρ-T) curves, it was clear that resistivity rose with the increase of K-concentration. Notably, the peak temperature coefficient of resistivity (TCR) and temperature (T_k) decreased as x rose in this study. This result was attributed to the disorder of cation size on A-site (\({\sigma }^{2}\)), which induced lattice strain leading to the random displacement of O²⁻ ions. Further, it led to the distortion of MnO₆ octahedron that promoted the localization of electrons, thereby reducing T_k. Moreover, the maximum value of TCR reached 7.60% K⁻¹ at 299.31 K (for x = 0.15). This result suggested that the Pr_0.6(Sr_0.85K_0.15)_0.4MnO₃ ceramic was befitting for application in advanced uncooled infrared bolometers.