Compositional tailoring of the thermal expansion coefficient of tantalum (V) oxide

The effect of Al2O3 and Nb2O5 additions on the microstructure and thermal expansion behavior of tantalum (V) oxide has been studied. Both singly doped and co-doped compositions were examined. Compositions with 3 wt% Al2O3 (or greater), contained AlTaO4 as a second phase. Complete solubility was observed for Nb2O5 contents in the range 1–5 wt%. It was found that doping with Al2O3 results in a decrease of the coefficient of thermal expansion (CTE), such that increasing amounts of Al2O3 (1–5 wt%) cause a successive decrease in the CTE value. In the case of Nb2O5 additions, the result is an increase in the CTE of the tantalum (V) oxide. However, in the range 1–5 wt% Nb2O5, the CTE value is relatively insensitive to the amount of Nb2O5 added. Due to the countervailing influences of these two additive oxides, it was demonstrated that co-doping with Al2O3 and Nb2O5 is an effective strategy for tailoring the CTE of tantalum (V) oxide.