Alkali Lithosilicates: Renaissance of a Reputable Substance Class with Surprising Luminescence Properties

A hitherto unknown synthetic access to alkali lithosilicates, a substance class first described by Hoppe in the 1980s, is reported. With the synthesis and characterization of NaK 7 [Li 3 SiO 4 ] 8 , a new representative has been discovered, expanding the family of known alkali lithosilicates. Astonishingly, NaK 7 [Li 3 SiO 4 ] 8 and the already established alkali lithosilicates Na[Li 3 SiO 4 ] as well as K[Li 3 SiO 4 ] display unforeseen luminescence properties, when doped with Eu 2+ . Na[Li 3 SiO 4 ]:Eu 2+ exhibits an ultra‐narrow blue, K[Li 3 SiO 4 ]:Eu 2+ a broadband, and NaK 7 [Li 3 SiO 4 ] 8 :Eu 2+ a yellow‐green double emission upon excitation with near‐UV to blue light. Consequently, all of the investigated substances of this class of compounds are highly interesting phosphors for application in phosphor converted LEDs.