HYDROGEN BONDS IN LITHIUM NIOBATE CRYSTALS OF DIFFERENT COMPOSITION

Abstract

An analysis of complex defects was carried out by IR-spectroscopy method in the area of OH- groups stretching vibrations. The defects are caused by hydrogen bonds present in the structure of nominally pure congruent lithium niobate crystals, crystals of stoichiometric composition with a different Li/Nb ratio, as well as in LiNbO3:Zn(0,04-6,5 мол.% ZnO) crystals doped in a wide range of concentrations due to direct doping of the melt method. Dopants were determined to influence OH-groups concentration, type and localization of complex defects in the crystals structure. A change in the amount of hydrogen sites in the LiNbO3 crystals structure was shown to evaluate the composition either stoichiometric or congruent. The character of OH-groups complexing with cation sublattice point defects was shown to change when doped crystals LiNbO3:Zn(0,04-6,5 мол.% ZnO) trespass concentration thresholds. Dopant incorporation mechanism changes at this drastically, thus crystal properties also change quite sharply. Frequencies (as well as quasi-elastic constants of OH-bonds) change in congruent and doped crystals due to a difference in electronegativities and ionic radii of the main and dopant cations.

Keywords

• single crystal
• lithium niobate
• defects
• ir absorption spectra
• doping
• stretching vibrations of oh-group