In the paper, the temperature dependences of the differential thermal analysis signal, permittivity, and amplitude of the third harmonic of the (KNO3)1–х/Snx composites have been studied. It was shown that the temperature of the α → β phase transition decreased by 2 – 3 K in the potassium nitrates being parts of the composites, and the temperature of the γ → α phase transition decreased up to 360 K. This result can be explained within the framework of the Landau – Ginzburg theory, taking into account the shielding of potassium nitrate particles by tin metal particles.