Dielectric tunability of 0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃ porous ceramics with oriented pore structure

The dielectric tunability of dielectric materials has potential application value in many devices. The introduction of porous structures is beneficial to broaden the range of dielectric constants of ceramics and improve their dielectric tunability. In this study, the porous ceramics of 0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃ (BNT-6BT) were prepared using walnut shell as a sacrificial template. The addition of walnut shell powder produces an ordered columnar porous structure within the ceramic, resulting in porosity ranging from 0 to 20%. Porous ceramics show lower dielectric constants, but higher tunability. There is an improvement in the dielectric constant stability of porous ceramics. The ceramic layer between the ordered pores provides an effective barrier to microstress and strain in the vicinity of the pore structure, so that the longitudinal piezoelectric coefficient d₃₃, and the transverse piezoelectric coefficient d₃₁ decrease slowly with increasing porosity, maintaining the desired piezoelectric properties. The porous BNT-6BT ceramics studied in this paper can be used in piezoelectric transducers, broadening their potential applications.