Reactive Synthesis of a Porous Calcium Zirconate/Spinel Composite with Idiomorphic Spinel Grains

Porous CaZrO 3 /MgAl 2 O 4 composites were synthesized in air by pressureless reactive sintering of an equimolar mixture of dolomite (CaMg(CO 3 ) 2 ), monoclinic zirconia ( m ‐ZrO 2 ), and α‐alumina powders, with a 0.5 wt% lithium fluoride additive. The reaction behavior of the mixed powders (with/without LiF additive) was studied using high‐temperature X‐ray diffraction. A bulk porous composite resulted from sintering at 1300°C for 2 h (in a nearly closed container, so as to increase the LiF‐doping effect), which consisted of fine grains (CaZrO 3 and MgAl 2 O 4 , ∼0.5–1 μm) and well‐grown idiomorphic ones (MgAl 2 O 4 octahedra ∼ 2–4 μm). The idiomorphic spinel grains were located around the inner walls of relatively large pores. The composite showed appreciably high bending strength (σ f = 110 ± 8 MPa for a porosity of 31%). The porous CaZrO 3 /MgAl 2 O 4 composites can be applied as high‐temperature filters and lightweight structural components.