Light-triggered "on-off" switchable dielectric constant in (Bi_0.5Na_0.5)_0.94Ba_0.06TiO3 lead-free ceramics

Light control of dielectric properties is very significant to develop photo-dielectric devices. Here, light-triggered "on-off" switchable dielectric constant (e(r)) was observed in (Bi0.5Na0.5)(0.94)Ba0.06TiO3 lead-free ferroelectric ceramics, exhibiting unconventional photo-dielectric effect (PDE). The effects of light switch period (2-165 min), light intensity (20-100 mW/cm(2)), and wavelength (450-940 nm) on PDE were studied in detail. Variation in e(r) exhibits remarkable switch effect with changing light on-off, while dielectric loss remains almost unchanged, and conductivity is still as low as 10(-12) S/cm with excellent electrical insulation under light irradiation. The unconventional PDE exists in the high-frequency range =1 MHz and at the low-temperature of -100 ?. In addition to the thermal effect and light-induced change in domain behavior, it is believed that polarization of the trapped electron-hole pairs under an external electric field contributes to the increase in e(r), and the low mobility of the pairs contributes to low dielectric loss and low photoconductivity. The results exhibit that dielectric constant of the lead-free ceramics can be regulated via light, whilst the ceramics keep excellent electrical insulation, endowing the lead-free ceramics potential applications in photo-dielectric devices.