Dielectric behaviour of flux grown substituted crystals bearing composition SrGa(x)lnyFe(12-(x+y))O(19) (x = 5, 7, 9; y=0.8, 1.3, 1.0) is reported. Variation of dielectric constant (sigma(ac)), dielectric loss (tan 8) and ac conductivity (sigma ac) with temperature in the range 30-500 degrees C under the frequency of the applied ac field in the range 1-10(4) kHz for all the varied compositions are analyzed and explained. Swift heavy ion irradiation effects on these parameters are dielectric constant (is an element of '), dielectric loss (tan delta) and ac conductivity (sigma(ac)). The frequency variation of is an element of ' and tan delta is explained by Koop's phenomenological theory and hopping frequency of electrons between Fe2+ and Fe3+ on octahedral sites for both irradiated and unirradiated crystals. (c) 2007 Published by Elsevier B.V.