Ultra-sensitive photodielectric effect in Sn-doped LaNb₃O₉ ceramics

Non-stoichiometric oxide semiconductors have great potential in the development of optoelectronic devices due to the observable photodielectric effect (PDE). In this work, LaNb₃O₉ (LNO) and B-site doped LaNb_2.85Sn_0.15O_9+δ (LNS) were prepared by solid state reaction method. LNS further exacerbate the lattice distortion induced by octahedral tilting, produce more fluctuating elastic stress/strain fields, and increase the energy band widths, leading to more pronounced grain boundary effects. Both LNO and LNS samples exhibit two dielectric relaxation phenomena (R1 and R2) in the temperature range from 77 K to 370 K. The R1 relaxation originates from the Maxwell-Wagner effect, while the R2 relaxation is mainly associated with polaron relaxation. Under room-temperature light irradiation, the photoinduced effect showed transient nature and disappeared rapidly after the light source was turned off, indicating that photoexcited electrons and holes are the main sources of PDEs. The dielectric constants (ε′) of LNO and LNS materials increased significantly under light irradiation. The doped sample LNS obtains up to 920 % PDE in the low-frequency region (50 Hz) at room temperature, reaching the highest PDE response level at the current experimental level, which is much higher than that of other photodielectric materials. It is also interesting to note that the dielectric loss under light is instead reduced. These experimental results indicate that LNS materials provide strong support and potential application value for the development of next-generation optically-driven microelectronic devices by virtue of their remarkable photodielectric effect, low dielectric loss and stable relaxation behavior.