Properties of porous glasses with embedded ferroelectric materials

Methods of introducing two ferroelectric materials, viz. NaNO₂ and (CH₃NH₃)₅Bi₂Cl₁₁ (PMACB), into porous glass matrices and the results of dielectric, pyroelectric, thermal expansion and SEM investigations are presented. The best filling degree was achieved for NaNO₂ introduced from the melt, whereas a significantly worse filling effect was achieved for a water solution as the introducing agent. A splitting was observed in the temperature dependence of dielectric permittivity related to the incommensurate phase of NaNO₂ embedded in porous glass from a water solution, whereas no incommensurate phase was observed in the case of glass filled with NaNO₂ from the melt. The confined materials turned out to possess ferroelectric properties and exhibited phase transitions. The negative size effect was observed for porous glasses filled with NaNO₂ and PMACB. The above conclusions are based on the anomaly of dielectric, pyroelectric and dilatometric properties observed in the phase transition regions.