Abnormal photo-dielectric effect of porous (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics: Effect of pores

The change in dielectric constant (εr) induced by light irradiation is known as the photo-dielectric effect (PDE). Light irradiation always causes an increase in εr, as reported in various materials including dense (Bi0.5Na0.5)0.94Ba0.06TiO3 (denoted as BNBT) lead-free ceramics. In contrast, we observed a distinct decrease in εr for the porous BNBT (denoted as BNBT-P) ceramics under light irradiation. Moreover, it is amazing to found that conductivity of BNBT-P also decreases under the light irradiation, which is counter-intuitive from the universal phenomenon. The mechanism for the abnormal PDE of BNBT-P was discussed. It is suggested that the aggregation of electrons around the pore regions under the light irradiation is responsible for the abnormal PDE. It is expected that the findings further promote understanding the origin of PDE.