Substitutional behavior and dielectric property of x(Na0.5K0.5)NbO3–(1−x)BaTiO3 using x-ray absorption fine structure spectroscopy

The doping effect of (Na0.5K0.5)NbO3 (NKN) on the dielectric properties of BaTiO3 have been investigated through the local atomic structure analyses. The dielectric constant of a specimen with x=0.05 was about 105% higher than that of pure BaTiO3. Through Ti K-edge x-ray absorption near edge structure (XANES) spectroscopy, it could be determined that the improved dielectric properties are due to the donor substitution by Nb-doping in the B-site. An increase in the XANES intensities with x indicates an increase in degree of hybridization, relating to the donor level, which leads to an increase in conduction electrons. Thus, the enhancement of the dielectric properties is attributed to the increased polarization interaction between the conduction electrons and the relaxation mode. The polarization of the electrons is confirmed by the comparative analysis of bond length data between Ti O and Nb O, derived from Ti and Nb K-edge extended x-ray absorption fine structure (EXAFS) spectroscopy.