Spark Plasma Sintering of Dielectric BaTaO2N close to the Melting Point of the BaCN2 Additive

Abstract The perovskite-type oxynitride BaTaO2N is a promising lead-free relaxor ferroelectric material. However, this material releases a part of its nitrogen during its sintering above 1350 °C. Subsequent annealing of the resulting sintered BaTaO2N0.85 ceramics under an ammonia flow is necessary to recover an insulating, stoichiometric BaTaO2N ceramics. Very recently, molten BaCN2 was reported to be a useful flux for the preparation of BaTaO2N microcrystals without the loss of nitrogen. In the present work, BaTaO2N powder was sintered with a BaCN2 additive under mechanical pressure, using a spark plasma sintering system. Nitrogen loss from the BaTaO2N ceramic was avoided during liquid phase sintering at approximately 900 °C. The stoichiometric BaTaO2N ceramic product with a relative density of 79.8% was an electrically insulator and it showed its relative dielectric constants, er, in the range from 320 to 650 and a loss tanδ values from 0.04 to 0.19 at room temperature.