Abstract Scope |
Classic oxide perovskite ferroelectrics usually exhibit large photonic bandgaps that are beyond the majority of visible light. Reducing the bandgaps deeply into the visible range may benefit many potential applications where interactions among light, conductivity, and domain wall motion occur. This work introduces a method of constructing a heterojunction between a polar perovskite phase and a polar tungsten bronze phase by introducing A-site vacancies into the Ba/Ni codoped (K,Na)NbO3 ceramics. Within the junction, the bandgap is minimized, and the ferroelectricity is optimized, resulting in a direct bandgap of ~2 eV and spontaneous polarization of 0.25 C/m2 simultaneously. The mechanism for bandgap reduction is identical to that for a semiconducting heterojunction, and the ferroelectricity optimization mimics what occurs in a morphotropic phase boundary. This work provides an alternative to the method of B-site engineering, where significant compromise on ferroelectricity is inevitable. |