Disclosed are non-stoichiometric Copper Alkaline Earth Silicate phosp hors activated by divalent europium for using them as high temperature stable luminescent mat erials for ultraviolet or daylight excitation. The phosphors are represented as the formula (BauSryCawCux)3−y(Zn,Mg,Mn)zSi1+bO5+2b:Eua. The non-stoichiometric tetragonal silicat e is prepared in a high temperature solid state reaction with a surplus of silica in the starting mixture. Furthermore, luminescent tetragonal Copper Alkaline Earth Silicates are provided for LED applications, which have a high color temperature range from about 2,000K to 8,000K or 10,000 K showing a CRI with Ra=80˜95, when mixed with other luminescent materials.