The optical properties ofNi2+dopedRb1−xCsxCaF3andRbCa1−xCdxF3solid solutions were studied. The1T2g(1D)→3A2g(3F)and1T2g(1D)→3T2g(3F)emission bands and the lifetime of the1T2glevel were measured as a function of the crystal composition. Both the band positions and the lifetime show a monotonic change withxbetween the values corresponding to the pure crystals. InRb1−xCsxCaF3crystals the contributions of differentNi2+centers in the emission bands were resolved. The shift of emissions is due to theRb+–Cs+substitution as next nearest neighbors ofNi2+ions as well as to a change of the lattice parameter with the composition of solid solutions. Both contributions were separated for some of theNi2+centers. ©1997 American Institute of Physics.