Modulation of Ferroelectric and Optical Properties of La/Co-Doped KNbO3 Ceramics

The phase transition, microscopic morphology and optical and ferroelectric properties are studied in a series of La- and Co-doped KNbO3-based ceramics. The results show that the doping induces the transformation from the orthorhombic to the cubic phase of KNbO3, significantly reduces the optical bandgap and simultaneously evidently improves the leakage, with a slight weakening of ferroelectric polarization. Further analysis reveals that (i) the Co doping is responsible for the obvious reduction of the bandgap, whereas it is reversed for the La doping; (ii) the slight deterioration of ferroelectricity is due to the doping-induced remarkable extrinsic defect levels and intrinsic oxygen vacancies; and (iii) the La doping can optimize the defect levels and inhibit the leakage. This investigation should both provide novel insight for exploring the bandgap engineering and ferroelectric properties of KNbO3, and suggest its potential applications, e.g., photovoltaic and multifunctional materials.

Automated summary

Doping of La and Co in KNbO3 ceramics leads to a phase transition from orthorhombic to cubic, reducing the optical bandgap and improving leakage while slightly weakening ferroelectric properties. Co doping decreases the bandgap, while La doping has the opposite effect. La doping optimizes defect levels and inhibits leakage.