Preparation of thick dense ceramic films of dielectric BaTaO2N through electrophoretic deposition

Sintering of the ferroelectric perovskite oxynitride, BaTaO2N is still a big challenge, because nitrogen is partially released from the crystal lattice during high-temperature sintering. Post-sintering annealing under an NH3 flow is essential in order to compensate for this nitrogen loss and to recover the electrically insulating properties of the ceramic. However, fully densified bulk ceramics are nitrided only on their outer surface, while their interior remains semiconducting. In this work, thick ceramic films of the perovskite oxynitride with a high relative density close to 90% were fabricated using electrophoretic deposition and high-temperature sintering. The nitrogen loss was fully recovered during annealing under an NH3 flow, owing to the thickness of the sintered films being less than 100 μm. After annealing, the BaTaO2N ceramics consisted of 200 nm-sized particles with a dense microstructure. This is the first report of the fabrication of BaTaO2N ceramics with a relative density of 89%. The dielectric constant and dielectric loss were approximately 320 and 0.05 at 1 MHz, respectively.