Innovative materials for phosphor converted white light-emitting diodes are in high demand owing to the huge potential of the light-emitting diode technology to reduce energy consumption worldwide. As the primary blue diode is already highly optimized, the conversion phosphors are of crucial importance for any further improvements. We report on the discovery of the high performance red phosphor Sr[Li 2 Al 2 O 2 N 2 ]:Eu 2+ meeting all requirements for a phosphor’s optical properties. It combines the optimal spectral position for a red phosphor, as defined in the 2016 Research & Development-plan of the United States government, with an exceptionally small spectral full width at half maximum and excellent thermal stability. A white mid-power phosphor-converted light-emitting diode prototype utilising Sr[Li 2 Al 2 O 2 N 2 ]:Eu 2+ shows an increase of 16% in luminous efficacy compared to currently available commercial high colour-rendering phosphor-converted light-emitting diodes, while retaining excellent high colour rendition. This phosphor enables a big leap in energy efficiency of white emitting phosphor-converted light-emitting-diodes.

The rare earth borates RE2B8O15 (RE = La, Pr, Nd) were synthesized in a Walker-type multianvil apparatus under conditions of 5.5 GPa and 1100 °C. Starting from the corresponding rare earth oxides and boron oxide, the syntheses yielded crystalline products of all new compounds that allowed crystal structure analyses based on single-crystal X-ray diffraction data for La2B8O15 and Nd2B8O15. The compound Pr2B8O15 could be characterized via X-ray powder diffractometry. The results show that the new compounds crystallize isotypically to Ce2B8O15 in the monoclinic space group P2/c. The infrared spectra of RE2B8O15 (RE = La, Pr, Nd) have also been studied.

Starting from the recently published narrow band red phosphor SALON, a tunable oxonitride-phosphor can be derived by introducing disorder into the structure. To achieve this, the oxygen content of the reaction mixture is increased, thereby prohibiting the oxygen/nitrogen ordering observed in SALON. The resulting compound is isotypic to UCr4C4 and exhibits mixed oxygen/nitrogen and lithium/aluminum sites. Further variation of the oxygen/nitrogen ratio revealed that the structure remains stable over a wide range of compositions. The compound can therefore be described by the general sum formula SrAl2–x Li2+x O2+2x N2–2x with x ranging between 0.12 and 0.66. When doped with Eu2+, the title compound exhibits an intense luminescence upon excitation with blue light. The maximum of this emission varies depending on the oxygen content and can be tuned to values between 581 nm (x = 0.66) and 672 nm (x = 0.12).

Recently, Wang et al. (Z. Wang, J. Ha, Y. H. Kim, W. B. Im, J. McKittrick, S. P. Ong, Joule2018, 2, 914–926) predicted and discovered Sr2LiAlO4, a quaternary compound with a layered structure crystallizing in the monoclinic space group P21/m, and they refined the structure from PXRD data. Upon partially substituting strontium with europium, the substance exhibits a yellow broadband luminescence consisting of two overlapping emission bands. In this paper, the crystal structure of Sr2LiAlO4 is confirmed by additional SC-XRD measurements and a newly discovered polymorph of Sr2LiAlO4 is presented crystallizing in the orthorhombic space group Cmcm. When Eu2+ is incorporated, this polymorph exhibits only one of the emission bands present in the P21/m-polymorph. Additionally, two substitutional variants of Sr2LiAlO4 are presented along with their luminescence properties upon incorporating Eu2+. One with a partial substitution of strontium for barium, leading to a structure in space group Pnma, and one with a partial substitution of oxygen for nitrogen, exhibiting the structure in space group Cmcm. The structure-property relationships in the above mentioned compounds are discussed with regard to their luminescence performance.

Eu 2+ , light-emitting diodes, narrow-band red emitter, Sr[Li 2 Al 2 O 2 N 2 ] (SALON), UCr 4 C 4 -type phosphors