Hydrothermal synthesized AgNbO3 powders: Leading to greatly improved electric breakdown strength in ceramics

Silver niobate AgNbO 3 ceramics have been regarded as a promising lead-free material for energy storage applications. In present work, pure and fine AgNbO 3 powders were successfully fabricated via the hydrothermal method using AgNO 3 as the raw material. It is found that the reaction products show strong dependence on the molar ratio of NH 4 HF 2 :AgNO 3 :Nb 2 O 5 , pH value and reaction time. Pure AgNbO 3 powders were obtained when the process conditions are 3NH 4 HF 2 :2AgNO 3 : x Nb 2 O 5 with x ≤0.85 or y NH 4 HF 2 :2AgNO 3 :1Nb 2 O 5 with y = 4–5, pH = 5 and reaction time t ≥ 10 h. Benefitting from the hydrothermal synthesised AgNbO 3 powders, AgNbO 3 ceramics with fine-grain of ∼3.4 μm were obtained. The fine-grain leads to increased electric breakdown strength E b up to 250 kV/cm, which is the highest among the pure AgNbO 3 ceramics to our best knowledge. The further enhancement in E b and recoverable energy density could be highly anticipated if the antiferroelectric phase could be stabilized.