Space-charge-induced colossal dielectric constant and large flexoelectricity in Nb-doped BaTiO₃ ceramics.

This article focuses on the enhancement of dielectric and flexoelectric properties in BaTiO₃ (BTO) ceramics through donor doping with niobium (Nb). Nb doping at an optimal concentration of 0.3 mol. % significantly increases the dielectric constant to about 180,000 and the transverse flexoelectric coefficient to 387 μC/m, nearly 40 times that of undoped BTO. The study attributes these giant dielectric and flexoelectric responses primarily to interface polarization effects arising from surface barrier-layer capacitance (SBLC) and internal barrier-layer capacitance (IBLC) associated with Schottky barriers at grain boundaries and electrode interfaces. Excessive Nb doping leads to cation vacancies that reduce free electron concentration, weakening the semiconductor behavior and diminishing the enhanced properties. These findings provide insights into tuning flexoelectric responses via controlled donor doping for advanced dielectric and electromechanical applications.