Mn⁴⁺ activated LaMgAl₁₁O₁₉ (LMA/Mn⁴⁺) with red emitting phosphor was obtained by sintering under air conditioning. The X-ray diffraction pattern Rietveld refinement results reveal that three six-fold coordinated Al sites are substituted by Mn⁴⁺ ions. Furthermore, the chemical valence state of manganese in the LMA host was further confirmed through X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Photoluminescence emission (PL) and excitation (PLE) spectra of LMA/Mn⁴⁺ as well as the lifetime were measured, and the 663 nm emission is ascribed to the ²E_g→⁴A_2g from the 3d³ electrons in the [MnO₆]⁸⁻ octahedral complex. The emission spectrum matches well with the absorption of phytochrome. Temperature-dependent PL spectra show that the color changes of the phosphor at 420 K are 0.0110 for Δx and −0.0109 for Δy. Moreover, doping Zn²⁺ and Mg²⁺ ions in the host enhances the emission intensity of Mn⁴⁺ ions. These results highlight the potential of LMA/Mn⁴⁺ phosphor for a light-emitting diode (LED) plant lamp.

In this work, an aluminate silicate garnet phosphor, Y₂Mg₂Al₂Si₂O₁₂:Ce³⁺ (YMASG:Ce³⁺), exhibiting strong and broad yellow-orange emission, was successfully synthesized. Attributed to the double cation substitution of YAG:Ce³⁺, which led to a compression effect, a redshift was observed with respect to YAG:Ce³⁺. More importantly, a transparent phosphor-in-glass (PiG) sample was obtained by incorporating the phosphor YMASG:Ce³⁺ into a special low-melting precursor glass. The energy dispersive spectrometer (EDS) mapping analysis of the as-prepared PiG sample indicates that YMASG:Ce³⁺ was successfully incorporated into the glass host, and its powders were uniformly distributed in glass. The photoluminescence intensity of the PiG sample was higher than that of the powder due to its relatively high thermal conductivity. Additionally, the combination of the PiG sample and a blue high-power chip generated a modular white LED with a luminous efficacy of 54.5 lm/W, a correlated color temperature (CCT) of 5274 K, and a color rendering index (CRI) of 79.5 at 350 mA.