The article presents the results of a study of the microstructure of Li 1 -x Na x NbO 3 solid solutions by electron microscopy as a function of the concentration substitution (x = 0, 2, and 3 mol %). The introduc tion of a small amount of sodium niobate leads to considerable changes in the morphology of the crystal. Esti mation of the average grain size shows that the average size decreases from 34.9 µm (for LiNbO 3 ) to 4.94 µm, when 2 mol % NaNbO 3 is introduced. A further increase in the concentration of sodium niobate to 3 mol % leads to a decrease in the average grain size to 3.19 µm.

By X-ray diffraction, differential thermal analysis (DTA) and thermo-gravimetric analysis (TGA) were investigated BaFe12-xAlxO19 hexaferrites with various concentrations of Al (x = 0.3, 0.9 and 1.2). Crystal structure of compounds was determined, and it determined that under normal condition (P = 0 GPa, T = 300 K) they possess structure is hexagonal symmetry with the space group P63/mmc. Replacing Fe3+ ions Al3+ with ions, on account of reducing ion radius, decrease of indices of parameters was occurred. This crystal structure is saved in a temperature range 30 - 950 ºC and structural phase transition do not occur. Energy supplied to a system is fully swallowed by a system, monotonic decrease is occurred in TGA curve and in DTA curve endo and exo effects do not occur.

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