Metal−Insulator Transition Induced by Ce Doping in CaMnO₃

Abstract

Study of the perovskite-type manganites Ca1 - x Ce x MnO3 (0.00 ≤ x ≤ 0.25) has been carried out. The electrical resistivity values for these samples were measured in the temperature range from 300 up to 900 K and show that the doping of the phase CaMnO3 with cerium induces simultaneously a marked decrease in the electrical resistivity and a metal-to-insulator transition. This behavior is exceptional since such a transition has not been observed to date in these compounds for these experimental conditions and can be attributed to the formation of Mn3+ ions as a result of charge compensation. The values of metal-to-insulator transition temperature, T MI, change with Mn3+ amount. Further the carrier doping tends to suppress the semiconductor behavior of CaMnO3 and the T MI is attributed to charge ordering observed in these compounds around 255 K.

Electron transport in CaMnO3 − δ at elevated temperatures: a mobility analysis

“…Notice additionally that thermodynamic equilibrium data result in ΔH°v alues equal 0.8 and 0.35 eV in orthorhombic and cubic polymorphs of CaMnO 3−δ , respectively [30], which coincide fairly well with the calculated band gap values 0.7 and 0.46 eV [31]. Considering the known relation E σ =ΔH°/2+ E μ and neglecting the relatively small contribution of the mobility activation energy, we arrive at the estimation E σ ≈ 0.4 eV that is in a good match with the activation energy for conductivity in orthorhombic CaMnO 3−δ at 400-600°C [7,21].…”

“…Conductivity of n-type in CaMnO 3−δ with different stoichiometry is characterized with small values 0.02-0.16 eV of the activation energy E σ at 150-600 K [1,7,13,[20][21][22]. Heating in air at 400-600°C is accompanied with the increase of conductivity and with the increase of the activation energy E σ to about 0.4 eV [7,21].…”

“…Heating in air at 400-600°C is accompanied with the increase of conductivity and with the increase of the activation energy E σ to about 0.4 eV [7,21]. At first glance, this behavior might be related to oxygen depletion at heating.…”

Determination of three estrogens and bisphenol A by functional ionic liquid dispersive liquid-phase microextraction coupled with ultra-high performance liquid chromatography and ultraviolet detection

“…Dispersive liquid-phase microextraction (DLPME) is a popular technique for sample pretreatment. In DLPME, water immiscible extraction solvent is dispersed as fine droplets in sample solution with the existence of dispersive solvent, which make DPLME a rapid enrichment technique with low cost and high enrichment factors [18].…”

Metal-Insulator Phase Transition and Structural Stability in ‘Sb’ Doped CaMnO3 Perovskite

“…Thus the synthesis at a temperature less than the eutectic temperature of a mixture enhances the phase formation and control of particle size [11].High reaction temperature for phase formation, nonhomogeneous mixing and agglomeration are commonly found in synthesis of oxide materials by solid state reaction [12]. Hence, the decreased reaction temperature is one of the reasons for increased Metal -Insulator transition temperature to 431 K compared to literature value 420 K [13].…”