Phosphor, use of a phosphor and a process for the preparation of a phosphor

The invention relates to a fluorescent substance (1) having the formula (RE a Ca 1-a-b Ce b) 3 (Mg 1-c Al c) 2 (Al d Si 1-d) 3 O 12, wherein RE is at least one rare earth element, 0 ≤ a ≤ 1, b > 0, a + b ≤ 1, 0 ≤ c ≤ 1, 0 ≤ d ≤ 1, and c + d > 0, wherein the fluorescent substance has a cubic crystal system having the space group Ia 3̅d.