The site occupation of protons in lithiumniobate crystals

The structural positions of protons in lithium niobate crystals (congruent nominally pure, MgO-doped and MgO and Fe2O3 co-doped LiNbO3) have been dete rmined by H-1 nuclear magnetic resonance measurement. Among various possibl e oxygen triangle positions, the calculation of second moment based on our experimental results shows that the "rigid" protons substitute Li+ ions and locate on the longest O-O bonds (336 pm) within the oxygen triangles neare st to Li-site. According to this conclusion, OH- absorption bands in highly MgO-doped and Fe2O3 co-doped LiNbO3 are firstly considered to relate with the stretching vibration of Mg-Nb(2+)-OHLi- and Fe-Nb(3+)-OHLi-, respective ly. (C) 2000 Elsevier Science Ltd. All rights reserved.