Degradation Mechanism of Dielectric Loss in Barium Niobate Under a Reducing Atmosphere

We developed multilayer ceramic capacitors (MLCCs) of the type negative–positive zero (NP0) cofired with Cu inner electrodes using novel low‐loss barium niobates. The excellent dielectric properties of ceramics and compatibility between electrodes and dielectrics under a reducing atmosphere led to low loss character in the Cu‐MLCCs, even in the high‐frequency single‐layer capacitors. We also examine the atmospheric dependence on dielectric loss of barium niobates. The origin of degradation in dielectric loss under a highly reducing atmosphere is explained by the association of two loss mechanisms: the oxygen vacancies in NbO6 octahedra and the subsequent formation of a reduced second phase: Ba3Nb4+Nb5+4O15.