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 NaK7 [Li3 SiO4 ]8 , a new representative has been discovered, expanding the family of known alkali lithosilicates. Astonishingly, NaK7 [Li3 SiO4 ]8 and the already established alkali lithosilicates Na[Li3 SiO4 ] as well as K[Li3 SiO4 ] display unforeseen luminescence properties, when doped with Eu2+ . Na[Li3 SiO4 ]:Eu2+ exhibits an ultra-narrow blue, K[Li3 SiO4 ]:Eu2+ a broadband, and NaK7 [Li3 SiO4 ]8 :Eu2+ 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.