The influence of Al2O3 content on Al2O3-ZrO2 composite-textural structural and morphological studies

In this work binary Al2O3-ZrO2 composites with 25, 50, and 75%, wow Al2O3 were synthesized by the sol-gel method, to find out the better Al2O3 amount that improve the texture, structure, and morphology. The composites presented high surface area, porosity and microcrystalline structure due to high cations dispersion induced by a good intermingling of the components. We found that structure of Al2O3-ZrO2 composites include AlO4 (tetrahedral), AlO5 (pentahedral) AlO6 (octahedral) polyhedral units. An increment of AlO4 and AlO6 species for low Al2O3 amount in the composites was observed. This was possibly related with segregated particles caused by progressive removal of hydroxyl groups. Otherwise, for high Al2O3 amount the fraction of AlO5 species was high, this behaviour was associated with an appropriate distribution of cations within the network of the composites as derived from condensation reactions. A suitable distribution of the Al3+ and Zr4+ cations in the network of the composites is observable by Z-contrast where for high Al2O3 concentrations an homogeneous arrangement was observed. Besides, for low Al2O3 concentrations rods of ZrO2 with an average length at similar to 250 nm are observable. Finally, by XPS analysis the non-lattice and lattice oxygen ratio presented similar values for Al50Zr50 composite, associated with the same available vacancies where Al3+ and Zr4+ cations have mayor mobility in the bulk and the superficial of the composite.