PHASE TRANSITIONS IN FERROELECTRIC KN[O.sub.3]/[AI.sub.2][O.sub.3] NANOCOMPOSITES

The temperature dependences of the linear dielectric permittivity s' and the third harmonic coefficient [[gamma].sub.3[omega]] for nanocomposites obtained by embedding a KN[O.sub.3] melt into the pores of [Al.sub.2][O.sub.3] oxide films with diameters of 330, 190, and 100 nm are investigated. The measurements were carried out in the heating and cooling modes in the range from room temperature to 463 K. It was found that the structural phase transition from phase II to phase I of potassium nitrate in [Al.sub.2][O.sub.3]films shifts towards higher temperatures as compared to bulk KN[O.sub.3]. For KN[O.sub.3], the ferroelectric phase appears in the pores of 190 and 100 nm both upon heating and upon cooling. Keywords: potassium nitrate, nanocomposite, dielectric permittivity, third harmonic coefficient.