アルコキシド加水分解法によるLiTaO₃結晶の生成過程

抄録

LiTaO₃ was prepared by hydrolyzing an ethanol solution of lithium ethoxide and tantalum ethoxide with H₂O in N₂ atmosphere. The samples with 25, 45, 46, ......, 54, 55 and 75 mole percent of Li₂O (Li₂O/Li₂O+Ta₂O₅ mol%) were coprecipitated.
The as-prepared samples with 45 to 55 mol% Li₂O were amorphous, but crystallized to LiTaO₃ byheating at 500°C for 2 h. Stability range of LiTaO₃ solid solution phase below 1100°C could be determined from change of the lattice constants of LiTaO₃ ss in 45 to 55 mol% samples heated at temperatures up to 1100°C. The ranges of LiTaO₃ ss phase were 49.9 to 51.2 mol% at 800°C, 49.1 to 51.6 mol% at 950°C and 48.0 to 52.0 mol% at 1100°C. The lattice constants of stoichiometric LiTaO₃ heated at 1100°C for 20 h were a_c=5.153+0.001 A, and c_o=13.78+0.01 A.
The as-prepared sample with 25 mol% Li₂O was amorphous, and crystallized to LiTaO₃ and fl-Ta₂O₅
at 700°C. Above 800°C, LiTa₃O₈ was formed by the reaction of LiTaO₃ with β-Ta₂O₅. A disordered NaCl type of Li₃TaO₄ was formed from the as-prepared sample with 75 mol% Li₂O which changed to ordered tetragonal phase above 800°C.