Low-temperature synthesis of perovskite-type (Nd 1− xCa x)MnO 3 (0.0≤ x≤0.5) via polymerized complex route

Abstract

To synthesize perovskite-type (Nd 1− x Ca x )MnO 3 (0.0≤ x≤0.5) at relatively low temperatures as 1273 K, a homogeneous gel has been prepared by adding an equimolar amount of citric acid and ethylene glycol to the mixed aqueous solutions of Nd(NO 3) 3·5H 2O, Ca(NO 3) 2·4H 2O and Mn(NO 3) 2·6H 2O. By heating the gel, we could reduce the synthetic temperature of Ca-doped NdMnO 3. The oxygen content of the sample was slightly higher than 3.00 and independent of x. The crystallite and average particle sizes revealed maximum values, ca. 27.8 and. 56.0 nm, respectively, at x=0.1. The sample was an n-type semiconductor; the electrical conductivity ( σ) and Seebeck coefficient ( α) as a function of temperature ( T) were examined. Since the log σT−1000/ T and the α− T curves varied linearly, it is obvious that the sample exhibits the hopping conduction on the small polaron model.