Far-red-emitting LaSrRO4:Mn4+ (R = Al and Ga) phosphor: Synthesis and optical properties

LaSrRO 4 :Mn 4+ (R = Al and Ga) are prepared by the high-temperature solid-phase method in air. Their luminescence properties, crystal structure, concentration dependent spectra, time-resolved spectra, fluorescence lifetime, and luminous mechanism are systematically researched, respectively. Mn 4+ ion is the luminescence center of LaSrRO 4 :Mn 4+ (R = Al and Ga). The excitation spectra of LaSrRO 4 :Mn 4+ (R = Al and Ga) under monitored at 715 nm lie in the range 210 – 650 nm with two main excitation peaks at ∼360 nm and 520 nm. With the excitation at 360 and 520 nm, LaSrRO 4 :Mn 4+ (R = Al and Ga) emit far-red light and have the emission spectra covering the region from 650 to 800 nm due to the 2 E g  →  4 A 2g transition of Mn 4+ ions. The ideal Mn 4+ concentration in LaSrAlO 4 :Mn 4+ and LaSrGaO 4 :Mn 4+ are ∼ 0.4 mol% and 0.6 mol%, respectively. The spectral properties of samples verify the crystal field s via the Tanabe-Sugano energy level diagram of Mn 4+ ion. LaSrRO 4 :Mn 4+ (R = Al and Ga) have the emission spectra match with the absorption spectra of the plant photosensitive pigments red light and far-red light, which infers their promising application in plant growth light-emitting diode (LED) lamp