Facile colloidal route to prepare hierarchical micro-nanoporous MgO stabilized ZrO2

Fabrication of sintered pure ZrO<inf>2</inf>ceramics result in the generation of cracks due to 3–5 % volume expansion associated with the phase transformation of tetragonal phase (t-ZrO<inf>2</inf>) to monoclinic phase (m-ZrO<inf>2</inf>) during cooling. Typically, Y<inf>2</inf>O<inf>3</inf>, MgO, CaO, CeO<inf>2</inf>are added as dopants to stabilize and produce crack free ZrO<inf>2</inf>. Herein, we developed a single-step colloidal processing route for in-situ generation of MgO nanoparticles by hydrolysis and calcination reactions of magnesium acetate precursor present in the aqueous ZrO<inf>2</inf>slurry, that aids in manufacturing of crack-free ZrO<inf>2</inf>compact. X-ray diffraction analyses of sintered pure ZrO<inf>2</inf>showed 36 % t-ZrO<inf>2</inf>and 64 % m-ZrO<inf>2</inf>, while MgO doped ZrO<inf>2</inf>revealed 36–37 % t-ZrO<inf>2</inf>, 31–35 % m-ZrO<inf>2</inf>, 14–19 % cubic phase (c-ZrO<inf>2</inf>) and 13–15 % Mg<inf>2</inf>Zr<inf>5</inf>O<inf>12</inf>. The cubic phases and Mg<inf>2</inf>Zr<inf>5</inf>O<inf>12</inf>are responsible for reducing the lattice strain as shown by the Williamson-Hall analyses. Interestingly, addition of microparticles of ZrO<inf>2</inf>to MgO doped Zirconia further led to reduction of the lattice strain. Hierarchical micro-nanoporous MgO doped ZrO<inf>2</inf>specimens were fabricated by using sacrificial poly(methyl methacrylate) (PMMA) beads (6 μm diameter) in the slurry. The porosity amount and pore diameters were systematically controlled by interplay of PMMA amount (1, 5, 10 vol %) and sintering temperatures (1100, 1200, 1300 °C). Such hierarchical micro-nano porous ZrO<inf>2</inf>could be beneficial in the fields of biomedicine, membrane technology, sensors, energy storage, and thermal barriers applications.