Synthesis and Luminescence Properties of Amber Emitting La(7)Sr[Si(10)N(19)O(3)] : Eu(2+) and Syntheses of the Substitutional Variants RE (8‐x ) AE(x) [Si(10)N(20‐x )O(2+x )] : Eu(2+) with RE=La, Ce; AE=Ca, Sr, Ba; 0≤x≤2

The oxonitridosilicate La(7)Sr[Si(10)N(19)O(3)] : Eu(2+) and its substitutional variants RE (8‐x ) AE(x) [Si(10)N(20‐x )O(2+x )] : Eu(2+) with RE=La, Ce; AE=Ca, Sr, Ba and 0≤x≤2 were synthesized starting from REN, SrN/Ca(3)N(2)/Ba(2)N, SiO(2), amorphous Si(3)N(4) and Eu(2)O(3) as doping agent at 1600 °C in a radiofrequency furnace. The crystal structure of La(7)Sr[Si(10)N(19)O(3)] was solved and refined based on single‐crystal X‐ray diffraction data. La(7)Sr[Si(10)N(19)O(3)] crystallizes in the orthorhombic space group Pmn2(1) (no. 31). The crystal structures of the isotypic compounds RE (8‐x ) AE(x) [Si(10)N(20‐x )O(2+x )] were confirmed by Rietveld refinements based on powder X‐ray diffraction data using the single‐crystal data of La(7)Sr[Si(10)N(19)O(3)] as starting point. Crystal structure elucidation reveals a 3D network of vertex sharing SiN(4) and SiN(2)(N(1/2‐x/4)O(1/2+x/4))(2) (0≤x≤2) tetrahedra. When excited with UV to blue light, La(7)Sr[Si(10)N(19)O(3)] : Eu(2+) shows amber luminescence with λ (em)=612 nm and fwhm=84 nm/2194 cm(−1), which makes it interesting for application in amber phosphor‐converted light emitting diodes.