Strong correlation of the electrical properties, up-conversion photoluminescence, and phase structure in Er3+/Yb3+ co-doped (1-x)K0.5Na0.5NbO3-xLiNbO3 ceramics

Er3+ and Yb3+ co-doped (1-x)K0.5Na0.5NbO3-xLiNbO(3) (KNN-xLN: Er/Yb, x = 0.04-0.09) ceramics were prepared to investigate their phase structures and piezoelectric, ferroelectric, and up-conversion photoluminescence properties. With increasing LN content, x, KNN-xLN: Er/Yb ceramics at room temperature evolve from the orthorhombic phase to the polymorphic phase and finally to the tetragonal phase. All the ferroelectric and piezoelectric properties and the I-r/I-g ratio of integrated intensities of red and green emission bands reach maximum values within the polymorphic phase transition of the KNN-0.06LN: Er/Yb ceramic. In this work, we find a close correlation between the electrical properties, up-conversion photoluminescence, and phase structure of KNN-xLN: Er/Yb ceramics. This correlation is discussed based on the Judd-Ofelt and crystallographic symmetry theories. (C) 2015 AIP Publishing LLC.