A study of the formation of LiNbO3 in the system Li2CO3Nb2O5

Abstract The formation process of LiNbO 3 in the system Li 2 CO 3 Nb 2 O 5 was discussed from the results of non-isothermal or isothermal TG experiments and X-ray analysis. The mixture Li 2 CO 3 and Nb 2 O 5 in mole ratios of 1:3, 1:1 or 3:1 was heated at a rate of 5°C min −1 or at various temperatures fixed in the range 475 to 677°C. If the system has a composition of Li 2 CO 3 + 3Nb 2 O 5 or 3Li 2 CO 3 + Nb 2 O 5 , the reaction between Li 2 CO 3 and Nb 2 O 5 proceeds with CO 2 evolution to form LiNbO 3 at ca. 300–600°C, but Nb 2 O 5 or Li 2 CO 3 remains unreacted. A composition of Li 2 CO 3 + Nb 2 O 5 gives LiNbO 3 at 300–700°C. The diffusion of Li 2 O through the layer of LiNbO 3 is rate-controlling with an activation energy of 51 kcal mol −1 . The reaction between LiNbO 3 and Nb 2 O 5 gives LiNb 3 O 8 at 600–700°C. At 700–800°C, a slight formation of Li 3 NbO 4 occurs by the reaction between LiNbO 3 and Li 2 O at the outer surface of LiNbO 3 and the Li 2 O component of Li 3 NbO 4 diffuses toward the boundary of the LiNb 3 O 8 layer through the LiNbO 3 layer. The single phase of LiNbO 3 is formed above 850°C.