In this work, high-temperature solutions of the (0.4Na(2)O-0.6B(2)O(3))-BaO -((6-x)Fe2O3 + xCoSnO(3)) system have been investigated. The concentration and temperature regions for the crystallization of BaFe12-(x-y)CoxSnyO19 for four different degrees of cobalt and tin substitution -Fe/(Co+Sn) = 12/0, 11/1, 10/2 and 9/3- have been established. Using six compositions for each one of the above mentioned cases, hexaferrite single crystals have been grown by spontaneous nucleation. The volatility and the creeping of these twenty four solutions as well as the habit and distribution coefficients of Co2+ and Sn4+ of the single crystals obtained were also discussed. On the basis of these results, suitable solution compositions for the growth of Co2+ + Sn4+ substituted barium M-hexaferrites have been proposed.