Chromium effects on the transport properties in La0.7Sr0.3Mn1−xCrxO3

Transport measurements have been performed on La0.7Sr0.3Mn1−xCrxO3 using impedance spectroscopy technique, in order to study its electrical properties. The results indicate that the electrical properties of the material are strongly dependent on temperature and frequency. Evidences of temperature dependent electrical relaxation phenomena in the material have also been observed. Impedance spectrum analysis shows that the material can be described as a grain and grain boundary medium and permits to estimate the grain boundary contribution. Hopping mechanism dominates at small concentration. Electronic conduction is found to be dominated by thermally activated hopping of small polarons at high temperature and variable range hopping at low temperature. When the concentration of chromium increases, electrical behaviour of the material changes from semi-insulating to metallic behaviour. A regime of percolation appears and a metallic conduction becomes dominant.

► We analyse the variation of conductance with temperature and frequency.
► The material turns from semi-insulating into metallic behaviour with Cr concentration.
► Hopping mechanism dominates at small concentrations.
► When the concentration increases a regime of percolation appears.
► Relaxation and conduction process are attributed to the same defect.