Exploring grain size and composition effects on the functional properties of BaGexTi1-xO3 ceramics

This study investigates BaGe x Ti 1-x O 3 ceramics with varying compositions (x = 0.010, 0.018, 0.100) produced by solid-state reaction, exploring the impact of composition and sintering temperatures (1150 °C, 1200 °C, 1300 °C) on functional characteristics (low-field dielectric, tunability, ferroelectric switching). Increasing Ge amount and sintering temperatures enhances sinterability of BaGe x Ti 1-x O 3 to almost complete densification. Room temperature permittivity ranges from 1000 to 2000, with dielectric losses below 10%. For small Ge additions, the dielectric behavior and phase transitions mirror BaTiO 3 ceramics. Increasing Ge addition results in a slight increase of the Curie temperature. Dielectric relaxation mechanisms involve two activation energy ranges related to oxygen vacancies and ionic conduction. Ceramics with larger grain sizes exhibit well-defined ferroelectric P(E) loops, while fine-grained ones contain extrinsic contributions. The highest tunability performances are found for the lowest Ge additions, sintered at 1150 °C, which are able to withstand the application of the highest dc field. • Exploring the role of sintering conditions for BaGe x Ti 1-x O 3 ceramics (x ≤ 10%). • Ge additions have a strong influence on densification and ceramic grain size. • Critical grain size range of enhanced permittivity is detected at small Ge addition. • Ferroelectricity and non-linear dielectric behavior unaffected by Ge substitution. • 10% Ge ceramics show a fully non-hysteretic nonlinear dielectric character.