Size-Manipulable Synthesis of Single-Crystalline BaMnO₃ and BaTi_1/2Mn_1/2O₃ Nanorods/Nanowires

Abstract

We report a size-manipulable synthesis of single-crystalline nanorods/nanowires of barium manganite (BaMnO 3 ) and barium titanium manganite (BaTi 1/2 Mn 1/2 O 3 ) by using the composite-hydroxide-mediated approach. The synthesis cleanly yields nanorods with a hexagonal perovskite structure. Typical nanorods have widths ranging between 50 and 100 nm, and the lengths can be easily controlled by time and temperature or by adding a small amount of water during the synthesis process. Resistance measurement shows that a phase transition happened at 58 K on BaMnO 3 . The photoluminescence spectrum of BaTi 1/2 Mn 1/2 O 3 presents two emission peaks at wavelengths of 465 and 593 nm, corresponding to blue and green fluorescence. The ability to synthesize nanorod manganites of a desired length should enable detailed investigations of the size-dependent evolution of magnetism, magnetoresistance, nanoscale phase separation, and realization of a nanodevice of magnetic sensors.

Functional Nanowires

“…Liu et al 41 have demonstrated a generic approach for the synthesis of single -crystal complex oxide nanostructures of perovskites, spinels, and various hydroxides, including monoclinic, corundum, CaF 2 -struc tured, tetragonal, and metal hydroxides. 42,43 The method is based on a reaction between a metallic salt and a metallic oxide in a solution of composite hydroxide eutectic at ϳ200ЊC and 1 atm without using an organic dispersant or capping agent. This one -step synthesis technique is cost -effective, easy to control, and can be conducted at low temperature and normal atmospheric pressure.…”

Synthesis of Ba-doped CeO2nanowires and their application as humidity sensors

“…The Ba-doped CeO 2 is synthesized through the newly invented nanomaterial fabrication route of the CHM method [11][12][13][14][15]. In a typical reaction, a 9 g amount of mixed NaOH and KOH with a Na/K ratio of 51.5:48.5 is placed in a 25 ml covered Teflon vessel.…”

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

“…Normally carrier localization at the grain boundary changes the conductivity to semiconducting or insulating and carrier delocalization leads to metal like behaviour.The hopping is characterized by the parameter T 0 which is related to electronic density of states N(E f ) and radius of localization length(a) by T o = 18/k B N(E F )a 3 . High T 0 value indicates multiphonon hopping with a large increase in the localization length and increase in barrier height at the grain boundaries leads to insulating and if T 0 decreases, based on hopping range and energy, the material remains in the metallic state of mott's transition [8,19]. Size of the grain and width of grain boundary inthe order of ρ ρ nanometers (or the localization length 'a' (1/ )) will correspond to 100% spin polarization by tunneling mechanism [28,29].…”

“…Sb 2 O 3 during the synthesis acts not only as reactant but also as an additive for decreasing the reaction temperature for phase formation from 1200 0 C to 900 0 C. The decreased reaction temperature for phase formation is due to the change in the eutectic point [8] of the mixture of all the reactants since additives provide liquid -phase grain growth at low temperature [9,10]. 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].…”