Synthesis and luminescence properties of dark - red - emitting Mn4+ doped α-Al2O3 for professional LED grow light

Abstract

Red-emitting α-Al₂O₃:Mn⁴⁺ fluorescent powders were prepared by co-precipitation method and sintered at 1000 to 1500^oC in the air. Effects of sintering temperature and Mn⁴⁺ concentration on the optical properties of the materials were investigated. The X-ray diffraction (XRD) showed that the crystallinity of Al₂O₃ belonged to hexagonal with R₃C space group. The excitation spectrum consisted of two broad intense bands centered at 399 and 568 nm and was assigned to ⁴A_2g(F)→⁴T_1g(F) and ⁴A_2g(F)→⁴T_2g(F) transitions, respectively. Under the excitation wavelengths of 399 and 568 nm, the α-Al₂O₃:0.1% Mn⁴⁺ phosphors emitted efficient red light at 694 nm caused by ²E_g→⁴A_2g transition. A red LED is made by coating Al₂O₃:0.1% Mn⁴⁺ powder on a violet chip located in the dark red light region. These results showed that α-Al₂O₃:Mn⁴⁺ has the potential to produce red LED lightings for plants.