Nominal Lanthanum Niobate, a Versatile Additive for Reducing Grain Boundary Resistance in Conductive Ceramics

Abstract Conductive ceramics currently play a vital role in human life. In practical applications, most conductive ceramics are polycrystalline, and their overall conductivity ( σ total ) is influenced by both bulk and grain boundary resistances ( R bulk and R gb , respectively). While R bulk is mainly of academic interest, R gb often determines the quality of a conductive ceramic component. Currently, studies discussing the influence of specific methods on grain boundary resistances are typically related to individual ceramics. In this study, it is discovered that the addition of 0.5–3 mol% nominal LaNbO 4 significantly reduces the R gb of several well‐known conductive ceramics, such as rhombohedral NaSICON‐type Na + ‐ion‐conducting Na 3.4 Zr 2 Si 2.4 P 0.6 O 12 and Li + ‐ion conducting Li 1.5 Al 0.5 Ti 1.5 P 3 O 12 , Li + ‐ion‐conducting tetragonal perovskite Li 0.34 La 0.56 TiO 3 , oxygen‐ion‐conducting cubic fluorite 8 mol% Y 2 O 3 stabilized ZrO 2 , and electron‐conducting perovskite SrTiO 3 (sintered in a reducing atmosphere). In particular, for NZSP and LATP, the enhanced σ total reaches 9.3 × 10 −3 S cm −1 and 2.1 × 10 −3 S cm −1 at 25 °C, surpassing previously published results. Detailed investigations reveal that the microstructure of the grain boundaries in all the ceramics undergoes significant improvements. The findings elevate the importance of research on grain boundaries, inspiring the development of conductive ceramics with higher σ total for superior applications.