Electro-optic evolution driven by static and relaxational nano ferroelectric domains in KTa_{1-: x}Nb_xO₃

Polar nano-regions (PNRs), whose evolution and response mechanism are unclear, were identified to be responsible for the pivotal large electro-optic (EO) coefficients near the T_C in KTa_1-xNb_xO₃ (KTN) crystals. To investigate this phenomenon, the temperature dependence of its Raman spectrum, and of its linear effective and quadratic EO coefficients, were investigated. Our results showed that both the relaxational nano-domains driven by biased electric fields under ordered static domains and strong anisotropy determined by the deformation of the NbO₆/TaO₆ realize enhancements of EO properties in the vicinity of T_f. We expect this understanding of the dynamic EO characteristics to be valuable for developing photonic devices and for providing a basis for exploring the origin of giant EO and piezoelectric effects in disordered ferroelectrics and relaxors.