アルコキシド加水分解法によるLiTaO3結晶の生成過程

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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 ac=5.153+0.001 A, and co=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.
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