Thermodynamic and experimental approach of the effect of Si on the sintering of Y3NbO7. Issue 10 (August 2021) - Guené-Girard, Simon
Highlights: The Y3NbO7 pure phase is product by co-precipitation route and calcined at 1100 °C. One of the two powders contain Si. There is no differences between the two powders in term of structure or morphology. The two powders were sintered in air up to 1650 °C. The ceramic containing Si shows an improved densification. A relative density of 99 % is obtain. A liquid phase is present in the ternary diagram (Nb2O5-Y2O3-SiO2) for temperature superior to 1400 °C, explaining the increase of densification thanks to the increase of material transport in liquid phase. The ceramics containing silicon show the apparition of precipitates of silicate (Y2SiO5). Thermodynamic calculations allow to determine the apparition mechanism of these precipitates. Thanks to the europium doping of the powder, micro-luminescence was used to map the precipitates in the ceramic, showing the interest of this uncommon technic to characterize ceramics. Abstract: The effect of silicon on the natural sintering of Y3 NbO7 powders is studied. Characterizations shows that Si increases densification rate and grain growth but it also leads to the apparition of a secondary silicate phase. The silicate precipitation results from the segregation of silicon favored by matter transport through a liquid phase. The distribution of the secondary phase have been studied by electronic microscopy and mapped by micro-luminescence. Thermodynamic calculations of Gibbs energy of the different phase as well as binary and ternary phase diagrams have been conducted to support interpretation of the sintering experimental results.