Microstructure and crystallography of Al2O3-Y3Al5O12-ZrO2 ternary eutectic oxide grown by the micropulling down technique

The directional solidification of Al2O3-YAG-ZrO2 eutectic ceramic by a micro-pulling down (µ-PD) technique is investigated. The effect of the pulling rate (0.1-1 mm min−1) on the crystallography and the microstructure is discussed. This ternary eutectic system has a Chinese script microstructure and the eutectic spacing λ depends on the pulling rate υ following the law: λ=6.5υ−12 where λ is in µm and υ in µm/s as derived from the Jackson-Hunt model. With the lower pulling rates, all phases are oriented with the 〈100〉 direction parallel to the growth direction; however other orientations appear at the higher pulling rates. The Cr3+ ions R-lines emission in the sapphire phase in the ternary eutectic composite is measured to estimate the stress in the alumina phase which is also shown to depend on the pulling rate.