Decomposition Behavior of Ternary Compounds in the Al–Te–O System and Phase Equilibrium of Al2O3–TeO2 System Below 920 °C in Air

Ternary compounds in the Al–Te–O system have been considered as potential materials for Low-Temperature Co-fired Ceramics preparation. Two ternary compounds, Al 2 TeO 6 and Al 2 Te 2 O 7 , have been found in the Al–Te–O system under 920 °C in air. The decomposition behavior of these two compounds has been studied with Thermogravimetric Analysis-Differential Scanning Calorimetry (TGA-DSC) and equilibration experiments. Phase equilibrium of the Al 2 O 3 –TeO 2 system has also been experimentally investigated at ambient atmosphere, and corresponding phase diagram has been derived. Obtained results showed that Al 2 Te 2 O 7 , could only be found when TeO 2 was 66.7-70.0 mol pct and temperature was at 590 °C to 610 °C. Al 2 TeO 6 decomposed into Al 2 O 3 , TeO 2 (g), and O 2 (g) when temperature was above 920 °C. Al 2 Te 2 O 7 converted into Al 2 TeO 6 at 620 ± 2 °C, and then followed the decomposition path of Al 2 TeO 6 . In phase equilibrium study, when the initial sample started from the Al 2 O 3 –Al 2 TeO 6 region, Al 2 TeO 6 and Al 2 O 3 were found in quenched samples at the temperature range of 500 °C to 915 °C. When the initial sample started from the Al 2 TeO 6 –TeO 2 phase region, two solid phases, Al 2 TeO 6 and TeO 2 , could be found in samples prepared under 725 ± 2 °C. When the temperature was above 730 ± 2 °C, there were Al 2 TeO 6 and one oxide liquid phase. In the Al 2 Te 2 O 7 –TeO 2 region, all equilibrated samples had Al 2 Te 2 O 7 and TeO 2 .