The compounds , were synthesized. Compositions in the three binary systems were also prepared. Cathodoluminescence of these compositions activated with Ce3+ and Eu2+ was studied. It was found that the Ca and Sr feldspars formed complete solid solutions. In the systems feldspars and feldspars, only partial solid solutions are formed. The solid solubility limits are Both the Ce3+ ‐ and Eu2+‐activated phosphors give broad emission bands under cathode‐ray excitation. The peak positions of the emission for Ce3+‐activated phosphors are and those for Eu2+‐activated phosphors are The peak position of the cathodoluminescent emission of the solid solutions for both Ce3+ and Eu2+ as activators depends on the major alkaline earth cation in the host. No significant shift from the pure compound was observed.