Far-red-emitting Li6SrLa2Sb2O12: Mn4+ phosphor for plant growth LEDs application

[Display omitted] •Far-Red emission of Mn4+ in Li6SrLa2Sb2O12 is observed for the first time.•Mn4+ doped Li6SrLa2Sb2O12 can convert both UV and blue-green light into Far-Red emission peaking at 705 nm.•The Li6SrLa2Sb2O12: Mn4+ phosphor well meets the application of plant growth.•The crystal field strength (Dq) around Mn4+ ions in Li6SrLa2Sb2O12 host is 1996 cm−1. Novel far-red emission Li6SrLa2Sb2O12: Mn4+ garnet-like phosphors have been synthesized via traditional high-temperature solid-state reaction method. The as-prepared Li6SrLa2Sb2O12: Mn4+ phosphor has a broad excitation band in the range of 300−600 nm with four Gaussian fitting bands peaking at around 325 nm, 364 nm, 429 nm and 501 nm, respectively. It gives far-red emission peaking at 705 nm under both UV and blue-green excitation. The optimum doping concentration of Mn4+ is about x = 0.01 and beyond which the luminescence quenching takes place, caused by the dipole-dipole interaction induced energy transfer among the Mn4+ ions. When the temperature is raised up to 370 K, the emission intensity of Li6SrLa2Sb2O12: 0.01 Mn4+ drops to 50 % of that at room temperature. The investigation shows that Li6SrLa2Sb2O12: Mn4+ is a potential red phosphor matching NUV LED chips for plant growth application.