OH/OD-IR ABSORPTION-BANDS IN SRXBA1-XNB2O6

Single crystals of SrxBa1-xNb2O6 (SBN) with congruent composition (x = 0.61) and Sr0.61Ba0.39Nb2O6 crystals doped with various concentrations of cerium are grown with the Czochralski method. A subsequent doping of the crystals with protons and deuterons is performed either by hydrothermal high temperature treatment or by field supported hydrogen diffusion at elevated temperatures in humid atmosphere. The presence of the protons is revealed by the infrared absorption of the OH stretching vibration. This broad OH absorption band is essentially the same for Sr0.61Ba0.39Nb2O(6) and Sr0.61Ba0.39Nb2O6:Ce (0.025 wt% CeO2). It shows a polarization dependence with respect to the c-axis of the tetragonal tungsten bronze structure of SrxBa1-xNb2O6, the absorption being stronger for light polarized perpendicular to c than for light polarized parallel to c. The maximum of the OH absorption band is at nu(01,OH)($) over bar = 3496 cm(-1) (at room temperature) for light propagating parallel c. At nu(02,OH)($) over bar = 6817 cm(-1) the very weak first overtone of the OH stretching Vibration can be observed. An analogous absorption band of the fundamental OD stretching vibration is observed at nu(01,OD)($) over bar = 2581 cm(-1). The observed OH and OD vibrational transition wave numbers can be described very well by a Morse-type potential.