Synthesis, thermal analysis, and band gap of ordered and disordered complex rock salt Li3TaO4

The temperature ranges of phase stability were examined for the disordered and ordered polymorphs of complex rock salt Li3TaO4. The disordered Li3TaO4, having an average structure of face-centered cubic unit cell, could be obtained by heating a mixture of Li2CO3 and Ta2O5 to 650-800 degrees C, but transformed irreversibly to the ordered and monoclinic ll-Li(3)TaO(4 )at >= 820 degrees C. The thermal stability of ll-Li3TaO4 depended heavily on the sealing of the container. When heated in an open environment, ll-Li3TaO4 decomposed to LiTaO3 and Li2O at >= 1100 degrees C, but such a decomposition was significantly suppressed in a sealed container even at 1450 degrees C. Based on the differential scanning calorimetry, the enthalpy of formation of the disordered Li3TaO4 was estimated at-1680 kJ/mol, as compared with-2206 kJ/mol of ll-Li3TaO4 . The indirect band gaps of the disordered Li3TaO4 and ll-Li3TaO4 were measured to be 4.65 and 4.4 eV, respectively.

Automated summary

The temperature ranges for phase stability were studied for the disordered and ordered polymorphs of complex rock salt Li3TaO4. The disordered Li3TaO4 can be obtained by heating a mixture of Li2CO3 and Ta2O5, but it transforms irreversibly to the ordered and monoclinic ll-Li(3)TaO(4 ) at high temperatures. The thermal stability of ll-Li3TaO4 is heavily dependent on the sealing of the container.