Structural, electrical and optical properties of (K,Ba)(Nb,Ni)O3-δ electroceramics: Oxygen vacancy and grain size effects

KNbO3-based ferroelectric materials have been largely investigated as a result of many interesting physical properties that make them suitable for designing multifunctional electronic components. In particular, ferroelectric (1-x)KNbO3-xBaNi(1/2)Nb(1/2)O(3-delta) (KBNN) solid solutions have received special attention for optical applications, including for high-performance photovoltaic devices. In this work, KBNN ceramics were produced via conventional solid-state sintering, followed by a comprehensive study of their (micro)structural, electrical and optical properties. The processed data are analyzed and discussed in terms of the effect from structural oxygen-vacancy defects in such materials and from the grain size, in the specific case of the observed electrical response. Overall, the results suggest these perovskite-structured semiconducting ferroelectric oxides as a good alternative for solar cell applications.