Strong f‐f Excitation and Bright Red Emission in Cd4Gd1‐xEuxO(BO3)3 (0≤x≤1): Near‐UV LED Pumped Red Phosphor with Low Thermal Quenching

Abstract Searching efficient red phosphors under near‐UV or blue light excitation is practically important to improve the current white light‐emitting diodes (WLEDs). Eu 2+ ‐ and Mn 4+ ‐based red phosphors have been extensively studied. Here we proposed that Eu 3+ is also a promising activator when it resides on a noncentrosymmetric coordination site. We proved that Cd 4 GdO(BO 3 ) 3 is a good host, which has a significantly distorted coordination for Eu 3+ . A careful crystallographic study was performed on the solid solutions of Cd 4 Gd 1‐ x Eu x O(BO 3 ) 3 (0≤ x ≤1) by Rietveld refinements. The as‐doped Eu 3+ cations locate at the Gd 3+ site and are well separated by CdO 8 , CdO 6 and BO 3 groups; thus, only a slight concentration quenching was observed at ≈80 atom % Eu 3+ . Most importantly, the parity‐forbidden law of 4 f ‐4 f transitions for Eu 3+ are severely depressed, thus the absorptions at ≈393 and ≈465 nm are remarkable. Cd 4 Gd 0.2 Eu 0.8 O(BO 3 ) 3 can be pumped by a 395 nm LED chip to give a bright red emission, and when mixed with other commercial blue and green phosphors, it can emit the proper white light (0.3657, 0.3613) with a suitable R a ≈87 and correlated colour temperature ≈4326 K. In‐situ photoluminescence study indicated the low thermal quenching of these borate phosphors, especially under 465 nm excitation. Our case proves the practicability to develop near‐UV excited red phosphors in rare‐earth‐containing borates.