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Polycrystalline La 0.8 (Ca 0.12 Sr 0.08 )MnO 3 :mol%Ag  x  (LCSMO:Ag  x  , x = 0, 0.1, 0.2, 0.3 and 0.4) ceramics were synthesized by the sol-gel technique. Structural, electrical and magnetic properties of the LCSMO:Ag  x  ceramics were investigated in detail. X-ray diffraction (XRD) data analyses revealed that all the samples were crystalized in the orthorhombic structure with space group of Pnma . With the increase in Ag doping ( x ), the grain sizes of the LCSMO:Ag  x  samples increased and the amount of grain boundaries (GBs) decreased accordingly. At the same time, the Mn-O bond distance and the Mn-O-Mn bond angles changed correspondingly, leading to the slight increase in the lattice constants ( a , b and c ) and slight expansion of cell volume ( V ). For the LCSMO:Ag  x  sample with x = 0.3, the optimal values of temperature coefficient of resistivity (TCR) and magnetoresistance (MR) reached 16.22% K -1 (265.1 K) and 42.07% K -1 (270.48 K), respectively. In addition, the fitting analysis of ρ - T curves showed that the experimental data were consistent with the theoretical calculation data. In the T &lt; T  MI (metal-insulator transition temperature) region, the electrical conduction mechanism of LCSMO:Ag  x  was clarified by electron-magnon, electron-electron and electron-phonon scattering. In the T &gt; T  MI region, the resistivity data were interpreted by using the adiabatic small-polaron hopping model. Furthermore, in the entire temperature range, the phenomenological equation called the percolation model was used to explain the resistivity data and the phase-separation mechanism of ferromagnetic metallic (FM) and paramagnetic insulating (PI) phases. All the obtained results indicated that the improvement in the electrical properties of the LCSMO:Ag  x  samples was attributed to the doping of Ag, which changed the A-site (La, Ca and Sr ions) average ion radius, the Mn-O-Mn bond angles and the Mn-O bond distance. In addition, the grain size increased, which led to improvement in the Mn 4+ ion concentration and the GBs connectivity in the LCSMO:Ag  x  polycrystalline ceramics.

rsc advances

Improved electrical transport properties of polycrystalline La0.8(Ca0.12Sr0.08)MnO3 ceramics by Ag2O doping