Dielectric properties of fine-grained barium titanate ceramics

TLDR

The decreasing width of ferroelectric 90° domains is theoretically explained by the balance between elastic field energy and domain wall energy. The study examined dielectric properties, lattice, and microstructure of BaTiO₃ ceramics with grain sizes ranging from 0.3 to 100 µm. For grain sizes below 10 µm, the 90° domain width shrinks with the square root of grain diameter, and the dielectric and elastic constants become dominated by domain walls; permittivity peaks near 5000 at 0.8–1 µm but falls sharply below 0.7 µm as the lattice transforms from tetragonal to pseudocubic.

Abstract

Dielectric properties, lattice- and microstructure of ceramic BaTiO3 showing grain sizes of 0.3–100 μm were studied. At grain sizes <10 μm the width of ferroelectric 90° domains decreases proportionally to the square root of the grain diameter. The decreasing width of the domains can be theoretically explained by the equilibrium of elastic field energy and domain wall energy. The smaller the grains, the more the dielectric and the elastic constants are determined by the contribution of 90° domain walls. The permittivity below the Curie point shows a pronounced maximum εr ≊5000 at grain sizes 0.8–1 μm. At grain sizes <0.7 μm the permittivity strongly decreases and the lattice gradually changes from tetragonal to pseudocubic.