Strong red emission in Bi3+ and Mn4+ codoped Mg3.5Ge1.25O6 phosphors applied in optical agriculture

Bi 3+ and Mn 4+ co-activated Mg 3.5 Ge 1.25 O 6 phosphors were synthesized via a solid-state method in air. Codoping Bi 3+ into the matrix leads to effective enhancement of the deep-red emssion (659 nm) compared to Bi 3+ -free samples. The spectroscopic properties are discussed based on the Bi 3+ (6s 2 )→Ge 4+ (3d 10 ) metal-to-metal charge transfer and energy transfer between Bi 3+ and Mn 4+ . All samples emit deep-red emission ascribed to 2 E g → 4 A 2g transition of Mn 4+ . We have carried out the X-ray power diffraction (XRD), photoluminescence spectrum (PL), field emission scanning electron microscope (FESEM), fourier transform infrared spectroscopy (FT-IR) and UV–Vis absorption measurement to investigate the influences induced by Bi 3+ incorporation.