Phase development of laser floating zone (LFZ) fibers of Bi 2 SrO 2 Ca 2 Cu 4 O 1 1 (2224) nominal composition during isothermal annealing at 800-870 o C for 1.5-24 h is investigated. The as-grown fibers have axially aligned Sr 0 . 3 Ca 0 . 7 CuO 2 (''1/1'') dendrites of constant average thickness δ=7.8 μm, an interdendritic matrix with the Bi 4 Sr 4 CaCu 3 O 1 4 (''4413'') intergrowth, the Bi 2 Sr 2 CaCu 2 O 8 (''2212'') phase and CuO cubic grains. Primary ''1/1'' cuprate and ''4413'' constituent are metastable and soon react at T=<800 o C transforming into equilibrium phases, ''2212'', Sr 0 . 3 Ca 1 . 7 CuO 3 (''2/1'') and Sr 7 Ca 7 Cu 2 4 O 4 1 (''14/24''). The growth kinetics of ''2212'', ''2/1'' and ''14/24'' fit a parabolic dependence on time, revealing a diffusion controlled mechanism of reaction in the solid state with activation energies in the 170-400 kJ mol - 1 range. For T=<835 o C, the Bi 2 Sr 2 Ca 2 Cu 3 O 1 0 (''2223'') phase develops. The reaction rates of all phases are dependent on the volume fraction of ''1/1'' in the as-grown fibers. Although the growth mechanism of ''2223'' resembles that of ''2212'', by enrichment of the ''2212'' plates in Ca and Cu from ''2/1'' and CuO phases, the overall reaction is a four-step reaction with an activation energy close to 1.5 MJ mol - 1 . Present results confirm the ''2212''-''2223''-''2/1''-''14/24'' as the set of compatibility phases for the 2224 composition at 835-870 o C when the ''2223'' phase is thermodynamically stable in air.