Energy dispersive X-ray spectroscopy and scanning electron microscopy are used to study La 2 CuO 4 –La 1.56 Sr 0.44 CuO 4 composites with different annealing times. Maps of the strontium distribution for such systems are calculated and compared to experimental data obtained for the area of contact between two dissimilar granules. The coefficient of lattice diffusion of strontium is found. At the areas of contact between La 2 CuO 4 and La 1.56 Sr 0.44 CuO 4 granules, the strontium concentration corresponds to superconducting phase La 2− x Sr x CuO 4 with x = 0.05–0.25. The technological parameters of synthesis affect the size and number of superconducting and normal regions. Prolonged annealing lowers the gradient of the strontium concentration, which halts the increase in the size of the superconducting regions. This saturation confirms the diffusion front model.