Deep-red emitting Mg₂TiO₄:Mn⁴⁺ phosphor ceramics for plant lighting

In this study, deep-red emitting Mg₂TiO₄:Mn⁴⁺ phosphor ceramics were synthesized by the high temperature solid-state reaction method. The ceramics can be excited by the 465 nm blue light and had a narrow emission with a full width at half maximum (FWMH) value of 31 nm. The peak wavelength was located at 658 nm, which matched the demanded wavelength for photosynthesis. The crystal field strength (D_q) and the Racah parameters (B and C) were estimated by the Tanabe-Sugano diagram. The thermal conductivity of the Mg₂Ti_(0.999)O₄:0.001Mn⁴⁺ ceramic was 7.535 W/(m·K) at room temperature, which was one order of magnitude higher than that of the traditional packaging method using the silicone gel. A set of phosphor converted LEDs were fabricated by mounting the phosphor ceramics onto the 460 nm blue LED chips and the CIE coordinates can move from the blue region to the purple light region with the thickness of the ceramic increasing. These results indicated that the Mg₂TiO₄:Mn⁴⁺ phosphor ceramic was suitable for plant lighting when combined with a blue LED chip.