1. An illumination system comprising a radiation source and a monolithic ceramic luminescence converter comprising a composite material comprising at least one luminescent compound comprising at least one activator in a host lattice and at least one non-luminescent compound, wherein the luminescent compound and the non-luminescent compound each comprise silicon and nitrogen and wherein the host lattice and the non-luminescent compound are different materials, wherein the luminescent compound is an amber or red-emitting europium(II)-doped alkaline earth oxonitridoaluminosilicate compound of general formula Ba2?x?zMXSi5?yAlyN8?yOy: Euz, wherein M=Sr, Ca; 0?x?2, 0?y?4, 0.0005?z?0.06 and the non-luminescent compound is an alkaline earth oxonitridoaluminosilicate compound of general formula Ba1?xMXSi7?yAlyN10?yOy, wherein M=Sr, Ca, Eu; 0?x?1 and 0?y?3.