THE DISSOCIATION AND IONIZATION OF LINBO3 MELTS

The thermodynamic and kinetic behavior of LiNbO3 melts has been studied experimentally by differential thermal analysis (DTA). Theoretical modeling has been carried out for three cases and the predicted results matched to the experimental data: (1) the melt contains only one species and no chemical reactions are present during heating and cooling, (2) the melt contains three species and a dissociation/recombination reaction occurs between LiNbO3 and Li2O + Nb2O5 and (3) the melt contains seven species with both dissociation and ionization reactions occurring to form the additional species Li+, LiO-, Nb2O4V(O)2+ ,and O2-. The best fit, using the linear programming technique LINDO, was for case 3 with seven active species in the melt. DELTA-G - values, DELTA-H - values and reaction rate constants (beta - values) were found for the dissociation/recombination reaction as well as for the two ionization reactions. These values allowed the species populations to be calculated for both the congruent liquid (mole ratio of Li2O to Nb2O5 = k = 0.942) and the Nb - rich (k = 0.724) and Li - rich (k = 1.222) liquid cases studied experimentally by DTA at 1275-degrees-C.