Insight into a novel rare‐earth‐free red‐emitting phosphor Li₃Mg₂NbO₆:Mn⁴⁺: Structure and luminescence properties

Abstract

Red phosphor is indispensable to achieve warm white light in the white light diode (WLED) application. However, the current red phosphors suffer from high cost and harsh synthesis conditions. In this study, an oxide-based rare-earth-free red-emitting phosphor Li 3 Mg 2 NbO 6 :Mn 4+ (LMN:Mn 4+ ) has been successfully synthesized by a simple solid-state reaction method. The relationship between crystal structure and luminescence was investigated in detail. The site occupancy of the doping Mn 4+ ion in the LMN host has been discussed from the point of bond valence sum. How the coordination environment of doping Mn 4+ affects the energy level of doping Mn 4+ ion has been illustrated via the Tanabe-Sugano energy-level diagram. Moreover, warm white light has been obtained using LMN:Mn 4+ as compensator to the YAG:Ce 3+ . K E Y W O R D Scalculation, luminescence materials, Mn 4+ , phosphor, photoluminescence

Enhancing the luminescence performance of an LED-pumped Mn4+-activated highly efficient double perovskite phosphor with A-site defectsvialocal lattice tuning

“…The value of β 1 was calculated as 0.928, which is much less than 1 since the oxide matrix has stronger Mn 4+ –O 2− covalent bonds influenced by the significant nephelauxetic effect compared to the fluoride. 33 That is, the smaller Racah parameters B and C in the oxide matrix lead to the red-shift of the Mn 4+ -ion emission wavelength. Moreover, the emission center wavelength of Mn 4+ ions in the LMTO matrix can be predicted according to the following equation: 37 where β 1 is the nephelauxetic ratio 0.928 and the theoretical value of E ( 2 E g ) was calculated as 14 243 cm −1 .…”

“…Considering the valence and ionic radius, the Ta 5+ ion (CN = 6, r = 0.64 Å) sites are more suitable for the Mn 4+ ions (CN = 6, r = 0.53 Å) to occupy rather than the Mg 2+ ion sites (CN = 6, r = 0.72 Å). To investigate the properties of the crystal field environment in which the Mn 4+ ions are located, the polyhedral distortion index (DI) of the [TaO 6 ] octahedra in the LMTO matrix was calculated according to the following equation: 33 where n is the CN of the central ion, l av and l i are the average lengths of all bonds, and the bond lengths between the central ion and each coordination ion, respectively. In this study, the CN of Ta 5+ ions is six, and the bond lengths after Rietveld refinement are listed in Table S1 †.…”

Flux induced highly efficient and stable phosphor Sr2ScSbO6:Mn4+ for plant growth lighting

“…In the PLE spectra monitored at 700 nm, there are four excitation peaks, deconvolved using Gaussian fitting, located in the range of 200–600 nm, corresponding to the transitions of Mn 4+ –O 2− charge transfer band (CTB), 4 A 2 → 4 T 1 , 4 A 2 → 2 T 2 and 4 A 2 → 4 T 2 , respectively. 14,22–24 Fig. 3b reveals the DR spectrum of Sr 2 ScSbO 6 :0.003Mn 4+ phosphor, where the absorption coefficient increases with increasing Mn 4+ concentration.…”

Luminescence enhancement of Mn4+‐activated double‐perovskite phosphors for LEDs through a co‐replacement strategy

“…Therefore, Mn 4+ ions will replace Ta 5+ ions in the MLTO matrix, resulting in the formation of MLTO: Mn 4+ phosphor. The distortion indices ( D ) of [TaO 6 ] octahedra were investigated by their bond lengths, and information on the bond lengths of [TaO 6 ] is presented in Table S3 and calculated by the following equation 38 : $$$$\begin{equation}D = \frac{1}{n}\mathop \sum \limits_{i\ = \ 1}^n \frac{{\left| {{l}_i - {l}_{av}} \right|}}{{{l}_{av}}}\end{equation}$$$$where n is CN of the central ion, l i and l av represent the average bond length and the bond length between the central ion and each coordination ion, respectively. In MLTO: Mn 4+ phosphors, CN is 6, and the calculated value of D is 0.5%.…”

“…Therefore, Mn 4+ ions will replace Ta 5+ ions in the MLTO matrix, resulting in the formation of MLTO: Mn 4+ phosphor. The distortion indices (D) of [TaO 6 ] octahedra were investigated by their bond lengths, and information on the bond lengths of [TaO 6 ] is presented in Table S3 and calculated by the following equation 38 :…”