A novel Y3+ modified La3Li5Sb2O12:Mn4+ far-red-emitting garnet phosphor for plant cultivation
Mn 4+ -active far-red emitting garnet phosphors are attractive in plant cultivation for chemical/physical stability and emission band well matching with the phytochrome absorption. (La 1-x Y x ) 3 Li 5 Sb 2 O 12 : Mn 4+ (x = 0∼0.4) garnet phosphors were fabricated by solid-state reaction in this work. The powder could exhibit far-red emission centered around 717 nm (related to Mn 4+ 2 E g → 4 A 2g transition), with the highest luminescence quantum efficiency ( QE ) and thermal quenching temperature ( T 0 . 5 ) reaching 38.03 % and 520 K, respectively. Comparing with La 3 Li 5 Sb 2 O 12 :Mn 4+ , the properties have been improved significantly, with double in QE and 20 K higher in T 0.5 . Y 3+ cation substitution would lead a stronger crystal field (verified by D q /B calculation) and a less spin-orbit coupling (verified by EPR spectra), and result in a smaller energy splitting and centroid shifting in 2 E g level. Then the luminescent efficiency and thermal stability would be improved a lot. The work not only provides a new far-red-emitting phosphor but also offers a strategy for Mn 4+ -active luminescence material improvement.
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