Charge ordering analysis by electrical and dielectric measurements in Ca2-xPrxMnO4 (x=0-0.2) compounds

Ca2-xPrxMnO4 (0 <= x <= 0.2) polycrystalline ceramic powders were synthesized by sol-gel method. The Xray diffraction (XRD) profiles were indexed with a tetragonal and orthorhombic structure for Ca2MnO4 and Pr-doped compounds, respectively. Electrical properties were investigated by dc and ac electrical measurements. The dc measurements have revealed an insulating state for all compounds in 80-350K temperature range. Both dc and ac measurements have highlighted a charge ordering (CO) transition at T-CO = 233 and 245K for x = 0.175 and 0.2, respectively. The CO state was found to be accompanied by a jump of the hopping activation energy and a rapid rise of both dielectric permittivity and imaginary part of ac electrical impedance.(C) 2011 Elsevier B.V. All rights reserved.