Finite size effects in ferroelectric and antiferroelectric materials

We report a study of the size dependent effects in ferroelectric (FE) PbTiO3 and antiferroelectric (AFE) PbZrO3. The phase transition (T-c) has been monitored by dielectric measurements and differential scanning calorimetry (DSC). From a study of the fine particles prepared by coprecipitation and sol-gel techniques, we find that in both FE and AFE cases, with a decrease in the particle size, (a) the lattice constants change so that the unit cell becomes more symmetric, and (b) the phase transition becomes diffused. However, there is a marked difference in the frequency dependence of the T-c in the two cases. Thickness dependent studies in c-axis oriented PbZrO3 thin films (on Si) show that the films are ferroelectric below a thickness of 500 nm and antiferroelectric at higher thickness. (C) 1997 Acta Metallurgica Inc.