The effect of K+, Na+ doping on infrared emissivity of lanthanum manganites

摘要

The monovalent-doped lanthanum manganites La(1-x)A(x)MnO(3) (A = K and Na, 0.1 <= x <= 0.4) were prepared by a standard solid-state reaction method. The structure, infrared absorption, electron spin resonance (ESR) and infrared normal emissivity (epsilon(N)) in the 8-14 mu m waveband of the samples were systematically investigated. The samples are distorted rhombohedrals, and the formation of K4MnO4 and Na4MnO4 indicates that the solubility of K+ and Na+ ions in the system is low. Infrared absorption peaks around 927 cm(-1) lead to high emissivity value of the samples in the 8-14 mu m waveband, and the EN of the samples decreases with increasing doping level. K+ doped samples exhibit higher infrared emissivity value, due to higher transition probabilities indicated by the ESR spectra. The EN Of the samples remains constant in the temperature range 293-373 K.