Thermally Stable and Deep Red Luminescence of Sr_1–xBa_x[Mg₂Al₂N₄]:Eu²⁺ (x = 0–1) Phosphors for Solid State and Agricultural Lighting Applications

Abstract

The systematic substitution of Ba in the Sr site of Sr­[Mg2Al2N4]:Eu2+ generates a deep-red-emitting phosphor with enhanced thermal luminescence properties. Gas pressure sintering (GPS) of all-nitride starting materials in Molybdenum (Mo) crucibles yields pure-phase red-orange-colored phosphors. Peaks in the synchrotron X-ray diffraction (SXRD) data show a systematic shift toward smaller angles due to the introduction of the larger Ba cation in the same crystal structure. The photoluminescence property reveals that Ba substitution shifts the original emission wavelength of Sr­[Mg2Al2N4]:Eu2+ (625 nm) toward ∼690 nm for Ba­[Mg2Al2N4]:Eu2+. Thermal stability measurement of Sr1–x Ba x [Mg2Al2N4] indicates a systematic increase in stability from x = 0 to x = 1. X-ray absorption near-edge spectroscopy (XANES) results demonstrate the coexistence of Eu2+ and Eu3+. The red-shift and the enhanced thermal stability reveals that the distance of the emitting 5d level to the conduction band of Ba­[Mg2Al2N4]:Eu2+ is large. The ionic size mismatch of Eu occupying a Ba site reduces the symmetry, thereby further splitting the degenerate emitting 5d level and lowering the energy of the emitting center. The development of deep-red phosphors emitting at 670–690 nm (x = 0.8–1.0) offers possible candidates for plant lighting applications.

Cr3+-Sphere Effect on the Whitlockite-Type NIR Phosphor Sr9Sc(PO4)7 with High Heat Dissipation for Digital Medical Applications

“…The Tanabe–Sugano diagram describes how the Cr 3+ energy state changes with the crystal field strength (Figure S2). The commonly used parameter to measure the crystal field strength is 10 Dq / B , and the formula for 10 Dq / B is expressed as , E a ( 4 T 1g ) and E a ( 4 T 2g ) are the peak positions of the 4 T 1g energy state and 4 T 2g energy state in the absorption spectrum, respectively. According to this formula, the influence of covalency can be further calculated.…”

Tunable concentration/excitation-dependent deep-red and white light emission in single-phase Eu2+-activated Sc-based oxide phosphors for blue/UV-LEDs

“…Generally, the stronger the crystal field around Eu 2+ , the smaller the energy gap between the 4f ground state and 5d excited state, and the longer the emission wavelength. 4,48 To further elucidate the selective occupation of Eu 2+ in the Sr 3 Sc 4 O 9 matrix, the PL spectra of Sr 3 Sc 4 O 9 :xEu (x = 0.002, 0.008, 0.01 and 0.02) samples at 77 K are fitted with the Gaussian function, as shown in Fig. 7.…”

“…2 As such, pc-LEDs attract great enthusiasm and are widely used in full-spectrum general lighting, wide-color-gamut backlight displays and agricultural lighting. [3][4][5][6][7][8] In the field of agricultural lighting, sunlight is a necessary condition for plant growth but cannot meet the needs of further increasing the crop yield and regulating plant growth cycles due to the uncontrollability of its intensity, quality and cycle. Therefore, the development of artificial lighting systems has become a research hotspot in modern agriculture.…”

Short review on recent progress in Mn4+‐activated oxide phosphors for indoor plant light‐emitting diodes

“…Also, it is a rare‐earth element and expensive to be used in large‐scale production. [ 27,28 ] To overcome the aforementioned issues, Mn 4+ ‐doped phosphors have emerged as promising R light‐emitting phosphors due to the abundance of raw manganese ores and low production costs. Also, Mn 4+ with 3d 3 electronic configurations can be excited by near‐ultraviolet (UV) to blue light and emit intense R or FR emission in the 600–750‐nm spectral range.…”