We study the size dependence of the antiferroelectric-to-paraelectric phase transition in ultrafine particles of PbZrO 3 (with x-ray domain size down to ≈30 nm) prepared by the sol-gel method. The phase transition was investigated by means of dielectric and thermal measurements. The nature of the particle size dependence of various properties of antiferroelectric PbZrO 3 was found to be generally similar to that of typical 'displacive' ferroelectrics such as PbTiO 3 and BaTiO 3 . In both cases, a size-induced structural distortion towards the high-symmetry paraelectric phase appears to dictate the behaviour of the nanoparticulate system. Nanoparticles of 'order-disorder' systems such as NaNO 2 behave in a markedly different manner. With decreasing particle size, we observe an increasing deviation of the dielectric response from the Curie-Weiss behaviour. Certain physical situations that may lead to the observed smearing out of the transition in nanoparticles of PbZrO 3 and PbTiO 3 are discussed.

Cubic barium titanate (BaTiO 3) powder was synthesized by heating barium titanyl oxalate hydrate, BaTiO(C 2 O 4) 2 ⋅ ⋅4H 2 O (BTO) precursor in microwave heating system in air at 500°C. Heating BTO in microwave above 600°C yielded tetragonal form of BaTiO 3. Experiments repeated in silicon carbide furnace showed that BaTiO 3 was formed only above 700°C. The product obtained was cubic.

No abstract

No abstract