Ageing of low field dielectric constant and losses in (Hf, Zr)-doped BaTiO3 ceramics

Ageing properties of weak field dielectric constant and losses of (Rf, Zr)-doped BaTiO3 ceramics in various crystalline phases are studied, and compared with those of pure tetragonal BaTiO3 ceramics. At room temperature, the ageing process develops following two different mechanisms: a thermally activated ageing process in pure tetragonal ceramics and a defects diffusion for the doped ceramics. We consider that the main reason for the different ageing mechanisms is the crystalline symmetry, which influences the twinning process and the domain-wall dynamics. Our results prove that ageing of (Hf, Zr)-doped BaTiO3 ceramics depends on temperature by intermediate of the phase symmetry, which imposes the twinning rate and rearrangement of ferroelectric domains minimizing the elastic energy of the lattice.