Phase transition and dielectric properties of BaTiO3 ceramics containing 10 mol% BaGeO3

Dielectric properties and the cubic ⇆ tetragonal phase transition temperature of dense BaTiO3 ceramics containing 10 mol% BaGeO3, sintered between 840 and 1350 °C, have been investigated. The ceramic bodies were prepared from a nano-sized BaTi0.9/Ge0.1O3 powder consisting of both BaTiO3 and BaGeO3 phases. The addition of BaGeO3 leads to a reduction and broadening of the permittivity maximum, and to a small downshift of the paraelectric ⇆ ferroelectric phase transition temperature, compared to a pure BaTiO3 ceramic. Lower sintering temperatures and thus small grain sizes of the ceramics cause an additional reduction of the maximum permittivity down to 2800. Both DTA and dilatometric measurements reveal also a downshifting of the phase transition temperature, as well as a decrease of the latent heat.