TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preparation (Claimed): Preparation of (I) comprises (a) mixing reactants of binary nitrides, halides and oxides or their corresponding reactive forms and (b) thermally treating the mixture under reductive conditions.Preferred Components: The mixture contains 30-95 (preferably 60-88) wt.% of (I).The primary light source comprises a luminescent indium-aluminum-gallium-nitride compound of formula (Ini GajAlkN).The light source contains green-emitting luminescent substance. The luminescent substance is so arranged on the primary light source that the luminescent substance is illuminated in the light of the primary light source, while the green-emitting luminescent substance is illuminated mainly by the light which has already passed the red-emitting luminescent substance or scattered by the luminescent substance.The luminescent substance is arranged between the primary light source and the green-emitting luminescent substance.Either i, j, k = greater than or equal to 0; ori+j+k = 1Preferred Process: In step (b), the reaction is carried out at above 800 degrees C (preferably 1400-1800 degrees C). The step (b) is carried out in nitrogen/hydrogen-stream, preferably nitrogen/hydrogen/ammonia-stream. Preferred Definitions:    A = Sr;    x = 0.01-0.8 (preferably 0.05-0.6); and    y = 0.1-2.5 (preferably 0.22-1.8).    SPECIFIC COMPOUNDS - 5 Compounds (I) are disclosed i.e. europium-silicon-nitrogen-oxygen containing metallic compounds of formulae (Sr(1.5)Si5N(7.6)O(0.4):Eu(II)(0.3)x 2.3 SiO2) (Ia), (Sr(1.6)Si5N(7.6)O(0.4):Eu(II)(0.2)x 2.1 SiO2) (Ib), (Sr(1.4)Si5N(7.6)O(0.4):Eu(0.4)x 2.8 SiO2) (Ic), (Ba(1.76)Si5N(7.6)O(0.4):Eu(0.04)) (Id) and (Ca(0.35)Sr(1.41)Si5N(7.6)O(0.4):Eu(0.04)) (Ie).    EXAMPLE - Strontium nitride (4.0257 g), europium nitride (0.5301 g), strontium fluoride (0.1146 g) and silica (1.3707 g) were mixed in agate mortar. The mixture was poured into a corundum crucible that was covered with a molybdenum foil and transferred into a furnace. The mixture was heated for 8 hours at 1600 degrees C in nitrogen/hydrogen/ammonia stream. The material was then removed and washed for 3 hours in 1M hydrochloric acid solution, filtered, washed with water and dried to obtain europium-silicon-nitrogen-oxygen containing metallic compound (Ia).