Microstructure and variable emittance property of annealed La-Sr-Mn-O films

The La-Sr-Mn-O films were deposited on Si(100) substrates by DC magnetron sputtering and followed by air annealing at 973 K for 1 h. The microstructure and temperature dependence of total hemispherical emittance (epsilon(H)) of the annealed La-Sr-Mn-O films prepared at various processing parameters were investigated. The results indicated the films deposited at lower sputtering pressure and lower O-2/(O-2+Ar) volume proportion (R-O) were present in rhombohedral perovskite structure and the length of Mn-O bond was shorter. The metal-insulator transition temperature (T-MI) was higher. All of the annealed films showed the unique feature of variable emittance based on metal-insulator transition. The films showed low emittance at low temperature but high emittance at high temperature. Moreover, the epsilon(H) significantly changed in the vicinity of T-MI. The variability of total hemispherical emittance (Delta epsilon) and the temperature range with obvious emittance change could be adjusted by changing the processing parameters. The Delta epsilon could be 0.45 and Delta epsilon/epsilon(355) (epsilon(355) is the epsilon(H) at 355K) exceeded 50% for the annealed La-Sr-Mn-O films. Therefore, the annealed La-Sr-Mn-O films showed much potential for thermal control applications as smart thermochromic variable emittance materials.