Phase transitions of KIO$_3$ ferroelectrics in Al$_{2}$O$_{3}$-based nanoporous matrices

Temperature dependences of the linear permittivity $\varepsilon'$ and the third harmonic amplitude $\gamma_{3\omega}$ of composites prepared by introducing ferroelectrics KIO$_3$ into matrices of porous aluminum oxide Al$_{2}$O$_{3}$ with pore sizes of 240 nm were studied. It is found that the IV $\to$ III and III $\to$ II structural transition temperatures of potassium iodide in Al$_{2}$O$_{3}$ pores decrease by 5 K and 24 K, respectively, with respect to bulk KIO$_3$. The measurements of the dielectric properties do not reveal V $\to$ IV and II $\to$ I phase transitions in the composite samples.