Abstract

It has been found that the lattice parameters a and c of lithium niobate (LN) crystals grown from a congruent melt with addition of potassium (K) decrease, and for a K concentration of 6 Wt.% they reach values 5.1469 and 13,8594 Å, respectively, as opposed to 5.1497 and 13.8656 Å, respectively, for crystals grown from the same melt but without K. Comparison of these parameters with those for LN crystals grown from melts with different compositions shows that the addition of K to the melt leads to an increase in the Li/Nb ratio in the crystals. Also, crystals grown from the melt with a 6 Wt.% K have a practically stoichiometric composition. For explaining the physical and chemical bases of the results, a diagram of the two-phase system Li₂O–Nb₂O₅ has been considered as a good approximation to that of the ternary Li₂O-Nb₂O₅ system because of its previously determined very small distribution coefficient for K (K_eff <1 × 10⁻²). It is also very likely that an accumulation of K ions near the growth surface further controls the distribution of LN main elements and their entry into the lattice in their own positions.

© 1995 Optical Society of America