High temperature Seebeck coefficient, small-polaron conduction and work function of LiMn1.5Ni0.5O4 thin films

Abstract

We report on the high temperature Seebeck coefficient, conduction mechanism and room temperature work function of LiMn1.5Ni0.5O4 thin film prepared using the radio frequency sputtering technique. Cubic spinel LiMn1.5Ni0.5O4 thin film exhibits a room temperature average work function value of 4.94 eV. DC electrical conductivity exhibits a small-polaron hopping mechanism with the activation energy of 0.47 eV. The polaron radius, inverse localization length and the Debye temperature values of LiMn1.5Ni0.5O4 thin films are predicted using the variable range hopping model and Raman studies. The Seebeck coefficient and the power factor values for the LiMn1.5Ni0.5O4 thin film is seen to vary from −1000 to −600 μV K−1 and 0.09 to 0.5 μW mK−2, respectively, in the temperature range of 420 to 560 K. Electrical transport studies reveal the fact that the LiMn1.5Ni0.5O4 thin film posseses n type charge carriers with a high Seebeck coefficient, high power factor and small-polaron hopping conduction mechanism in the temperature range of 420–560 K.