Tremendous Acceleration of Plant Growth by Applying a New Sunlight Converter Sr<sub>4</sub>Al<sub>14−</sub><i><sub>x</sub></i>Ga<i><sub>x</sub></i>O<sub>25</sub>:Mn<sup>4+</sup> Breaking Parity Forbidden Transition
Shichuan Wang, Takatoshi Seto, Bin Liu, Yuhua Wang, Cancan Li, Zhengqiang Liu, Haowen Dong
Abstract
Abstract Majority of Mn 4+ activated oxide phosphors have the wavelength of excitation and emission suitable for acceleration of plant growth as light converter from sunlight to deep red. Here, it is observed that 60% increase of red emission of Sr 4 Al 14 O 25 :0.01Mn 4+ is found by substituting 0.1Ga 3+ . It is clarified that the increase is originated from a unique mechanism of breaking parity forbidden transition under the substitution of cation in d–d transition by using the tool of special aberration corrected transmission electron microscope(AC‐STEM), pre‐edge peak (1s→3d) Mn K‐edge X‐ray absorption near edge structure (XANES), extended X‐ray absorption fine structure (EXAFS), Rietveld analysis of X‐ray diffraction (XRD) patterns, and reflection spectra. Further, a combination of substituted Ga, Mg, and special double flux H 3 BO 3 /AlF 3 is found to tremendously increase the emission intensity (355% up). Actual growth of chlorella and rose is examined by a combination of the cheap Sr 4 Al 14 O 25 :0.01Mn 4+ ,0.007Mg 2+ ,0.1Ga 3+ and a unique reflection typed phosphor‐film system as sunlight converting system. Optical density of chlorella and height of rose grass is increased by 36±14% and 174±80% compared with nonphosphor‐film, respectively.