EFFECT OF ERBIUMOXDE (ErO) AMOUNT ON PHASE STABILITY, SINTERNG AND MCROSTRUCTURAL EVOLUTION OF CUBCZRCONA (c-ZrO)/ERBIUM OXIDE (Er2O3) NANO COMPOSITES

The effect of Er, O, amount on phase stability, sintering and microstructural evolution of cZrO/Er2O3 composites was investigated. Specimens containing up to 15 wt.% Er,0s were produced by colloidal processing and pressureless sintering. XRD analysis revealed that only cubic fluorite structure is the crystalline phase present in both pure c-ZrO, and ErO3 doped c-ZrO, specimens and there were no other diffraction peaks of second phase for all compositions. The lattice parameter of the c-ZrO, crystal decreased with increasing ErzOs amount up to 10 wit% and stayed constant after this amount. This result indicated that the Er,0s addition up to 10 wit% was completely solubilized in the c-ZrO2 matrix. After this amount, the supersaturated c-ZrO/Er2O3 solid solution could not solubilize more Er,0s and thus ErO3 mostly segregated around grain boundaries as thin layer. The grain size of undoped and Er:03 doped c-ZrO2 specimens decreased with increasing Er:O3 content up to 5 wt.% and almost did not change after this amount. The difference of the grain size in the undoped and Er,0s doped c-ZrO, specimens can be related to differences in segregation of the solute cations at grain boundaries. The relative density of the specimens increased with increasing sintering temperature and slightly decreased with increasing ErO3 content for all sintering temperatures. This decrease was probably resulted by the porosities formed in the matrix and around the grain boundaries. Microstructural investigations showed that the grains were aquiaxed, faceted and coarsened in the undoped c-ZrO2. Whereas, the grains were aquiaxed, uniform, more rounded and fined in the ErO3 doped c-ZrO, specimens.