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

Zixin Wang,Zhaoxia Han,Ruijin Hong,Shengming Zhou,Yang Li,Dawei Zhang,Yiming Shen,Lei Chen,Chunxian Tao,Hui Lin

doi:10.1007/s40145-020-0421-6

Abstract

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 (Dq) 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.

Highlights

In the past few decades, it has been proved that artificial light sources can improve the growth of plants [1]
The X-ray diffraction (XRD) positions of all samples were well corresponded to the ICSD 82912 card of Mg[MgTi]O4, indicating that the doping of Mn4+ did not transform the crystal structure
The Mg2TiO4 ceramics with different amounts of Mn4+ doping concentrations have been synthesized via the high temperature solid-state reaction method

Summary

Introduction

In the past few decades, it has been proved that artificial light sources can improve the growth of plants [1]. Due to the difference in the spectral drifting and the degradation rates between the red and the blue LED chips, the ratio of red light to blue light is unstable [8] To this end, another path to obtaining the stable light source for plant growth is using the red phosphor excited by the blue LED instead. Mn4+ doped fluorides have a strong excitation band corresponding well with blue LED chips, but the sharp red emission is usually peaked at < 640 nm [13], and the use of toxic HF solution is harmful to the environment. Mg2TiO4:Mn4+ is a promising red phosphor that can be excited by the blue LED for plant lighting. Translucent Mg2TiO4:Mn4+ ceramics were fabricated and the optical as well as the thermal properties were analyzed and discussed

Experimental

Results and discussion

B B0 2 C C0 2

A B1 exp t 1 B2 exp t 2

Conclusions