The effect of barium titanate admixture on the stability of potassium nitrate ferroelectric phase in (1–x)KNO3 + (x)BaTiO3 composites

The study of temperature evolution of the KNO3 structure in ferroelectric (1 – x)KNO3 + (x)BaTiO3 composites at х = 0.25 and 0.50 has been carried out on cooling and on heating using X-ray diffraction. It was shown that on cooling the phase transition temperature (Tc) from the high-temperature paraelectric phase into the ferroelectric one did not depend on barium titanate concentration and practically coincided with Tc for the pure KNO3. Simultaneously the admixture of BaTiO3 essentially enlarged the temperature interval of the KNO3 ferroelectric phase stability in these composites. Structure refinement did not confirm the suppression of the ferroelectric phase of potassium nitrate proposed previously for (0.5)KNO3 + (0.5)BaTiO3 sample on the basis of dielectric spectroscopy data. The transition from the ferroelectric phase into the low-temperature paraelectric α-phase was not observed in this composite on cooling down to 348 K.