Temperature dependence of total hemispherical emittance in perovskite-type manganese oxides, La_1-xSr_xMnO₃

La_1-xSr_xMnO₃ is a manganese oxide with a perovskite-type structure, LaMnO₃, by substitution of La³⁺ sites with Sr²⁺, which shows a variety of phenomena with changing hole concentration (x). The total hemispherical emittance, ε_H, of La_1-xSr_xMnO₃ (x = 0, 0.175, and 0.3) in the vicinity of the metal-insulator transition temperature was measured by the calorimetric method in the temperature range 173-373 K. Remarkable differences in ε_H resulted with changing hole concentration (x). It was observed that ε_H of La_0.825Sr_0.175MnO₃ changed notably at about 280 K accompanied by the metal-insulator transition and the maximum amount of variation in ε_H was 0.42. The effects of surface conditions and thicknesses of samples were also observed. The uncertainty in the measurement of ε_H was estimated to be at most ±2.2% from 173.15 to 373.15 K.