Electronic and Optical Properties of Strontium Barium Niobate Single Crystals

Abstract

Electronic structure of Sr _x Ba_{1- x} Nb₂O₆ crystals in the energy range involving the valence and conduction bands has been studied theoretically and experimentally using the DFT-based ab initio VASP code and the spectroscopic ellipsometry method with synchrotron radiation. The Sr_0.61Ba_0.39Nb₂O₆ sample of the congruently melting composition is characterized by the greatest difference of the experimental dielectric function ϵ(E) compared to the non congruently melting compositions of Sr _x Ba_{1- x} Nb₂O₆ (x = 0.40, 0.55, 0.65, 0.75). Electronic band structures of Sr_0.60Ba_0.40Nb₂O₆ and LiNbO₃ crystals in the energy range of 6–8 eV and the corresponding dielectric functions ϵ(E) in the photon energy range of 3–10 eV have been found to be similar, what is caused by similar octahedral NbO₆ complexes in the crystals.

Keywords:

• SBN crystal
• electronic structure
• optical properties

Acknowledgment

This work was supported by the European Community Research Infrastructure Action under FP7 (EC Grant Agreement no. 226716–ELISA) in the frame of the BESSY-projects 10.1.91004 and 10.2.100107. We also want to thank the Helmholtz-Zentrum Berlin (BESSY II) for help and support. Calculations of band structure and related properties of crystals were done partly at ICM of Warsaw University in frame of the project G26-3.