Microstructure and Optical Properties of La2Mo2O9 Doped Sodium Bismuth Titanate Ferroelectric Ceramics

Abstract: An internal electric field is created by the polarization of the ferroelectric ceramics, which separates photogenerated carriers and effectively reduces the recombination rate of carriers. However, the light absorption is limited by wide band gap of ferroelectric ceramics, so the further development of ferroelectric ceramics in the field of photovoltaic is hindered. In this paper, doping La₂Mo₂O₉ into Bi_0.5Na_0.5TiO₃ (BNT) ceramics with good ferroelectricity, to reduce the optical band gap and increase the photocurrent density. The samples were prepared by the conventional solid-phase synthesis method, and the XRD, Raman, light absorption, photocurrent, ferroelectric and dielectric properties of the ceramics were analyzed. The results show that the La₂Mo₂O₉ doping significantly increases the light absorption intensity. As the content of La₂Mo₂O₉ doping increases, the optical band gap first decreases significantly, and then slowly increases. The BNT-xLM ceramics with x=0.7% (mole fraction) exhibits the minimum optical band gap values with 1.57 eV, which is much lower than the 2.9 eV of pure BNT ceramics. The corresponding maximum photocurrent density and open circuit voltage are 71.06 nA/cm² and 4.40 V respectively, and the maximum output power obtained is 312.7 nW/cm², as well as the variation, is small with time maintaining excellent ferroelectricity. The research results show that La₂Mo₂O₉ modified BNT ferroelectric ceramics is a very promising ferroelectric photovoltaic material.

Key words: ferroelectric ceramics, photogenerated carrier, La₂Mo₂O₉, optical band gap, photocurrent, ferroelectric photovoltaic material