Structural, electrical and magnetic properties of La0.625Ca0.285Sr0.09MnO3 polycrystalline ceramics doped with Ag2O

Abstract

In this study, the doping effects of silver on the structural, electrical and magnetic properties of polycrystalline La0.625Ca0.285Sr0.09MnO3:Agx (LCSMO:Agxx = 0, 0.10, 0.20, 0.25, and 0.30) ceramics were investigated and the results were discussed. The ceramic specimens were prepared by the sol–gel method followed by sintering at 1673 K for 14 h. The optimization of ceramic properties, such relative high temperature coefficient of resistance (TCR) in the vicinity of room temperature was obtained by varying the Ag doping content. X-ray diffraction indicated that all specimens crystallized in typical orthorhombic perovskite phase with Pnma space group. Rietveld refinement data showed that structural parameters, such as Mn–O bond length, Mn–O−Mn bond angles and cell volumes were slightly modified when Ag content increased. Scanning electron microscopy depicted reduced grain boundaries and increased grain size when Ag content rose. Resistivity dependence of temperature curves (R−T) of LCSMO:Agx specimens were investigated by standard four-probe method, and R−T curves indicated decline in resistivity with Ag2O content. The specimen with x = 0.25 illustrated relatively high TCR value reaching 4.60%/K near room temperature (310.06 K). X-ray photoelectron spectroscopy revealed that Ag+ could increase Mn4+ ion concentration since Ag+ ion may replace La3+, Ca2+ and Sr2+ ions at A-sites. The magnetoresistance measured at low magnetic field of 0.8 T suggested enhancement in low field magnetoresistance of LCSMO:Agx ceramics with x. Overall, the prepared ceramics look promising for applications in bolometric infrared detectors.