Solution-processed BiFeO3 thin films with low leakage current

Large pyroelectric energy conversion in lead scandium tantalate thin films

Non-linear pyroelectric energy harvesting using ferroelectric thin films exhibits high energy conversion, primarily due to their large breakdown field compared to bulks. Here, we report the pyroelectric energy conversion potential of lead scandium tantalate, Pb(Sc1/2Ta1/2)O3 (PST) thin film fabricated on a c-sapphire substrate using chemical solution deposition. To enable the application of high electric field and to assess the pyroelectric energy conversion performance, interdigitated electrodes were deposited on the PST thin film. A maximum harvested energy density of 9.1 J cm-3 per cycle was deduced from polarization measurements in films undergoing an Olsen cycle between 0 °C and 150 °C when the electric field was varied between 50 and 1500 kV/cm. Furthermore, PST thin films can reach up to 27 % of Carnot efficiency for a temperature interval of 10 K between 30 °C and 40 °C. This study highlights the significance of PST thin films for electro-thermal energy harvesting and promising opportunities for enhancing the conversion efficiency and power density using thin films or thin film multi-layer capacitors in the future for thermal energy harvesting.

Increasing Electrical Resistivity of P-Type BiFeO3 Ceramics by Hydrogen Peroxide-Assisted Hydrothermal Synthesis

Bismuth ferrite (BiFeO₃, BFO) is still widely investigated both because of the great diversity of its possible applications and from the perspective of intrinsic defect engineering in the perovskite structure. Defect control in BiFeO₃ semiconductors could provide a key technology for overcoming undesirable limitations, namely, a strong leakage current, which is attributed to the presence of oxygen vacancies (V_O) and Bi vacancies (V_Bi). Our study proposes a hydrothermal method for the reduction of the concentration of V_Bi during the ceramic synthesis of BiFeO₃.Using hydrogen peroxide (H₂O₂) as part of the medium, p-type BiFeO₃ ceramics characterized by their low conductivity were obtained. Hydrogen peroxide acted as the electron donor in the perovskite structure, controlling V_Bi in the BiFeO₃ semiconductor, which caused the dielectric constant and loss to decrease along with the electrical resistivity. The reduction of Bi vacancies highlighted by a FT-IR and Mott-Schottky analysis has an expected contribution to the dielectric characteristic. A decrease in the dielectric constant (with approximately 40%) and loss (3 times) and an increase of the electrical resistivity (by 3 times) was achieved by the hydrogen peroxide-assisted hydrothermal synthesized BFO ceramics, as compared with the hydrothermal synthesized BFOs.