Tremendous Acceleration of Plant Growth by Applying a New Sunlight Converter Sr₄Al₁₄₋<i>_x</i>Ga<i>_x</i>O₂₅:Mn⁴⁺ Breaking Parity Forbidden Transition

Abstract

Majority of Mn⁴⁺ 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 Sr₄ Al₁₄ O₂₅ :0.01Mn⁴⁺ is found by substituting 0.1Ga³⁺ . 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 H₃ BO₃ /AlF₃ is found to tremendously increase the emission intensity (355% up). Actual growth of chlorella and rose is examined by a combination of the cheap Sr₄ Al₁₄ O₂₅ :0.01Mn⁴⁺ ,0.007Mg²⁺ ,0.1Ga³⁺ 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.