The reaction route and morphology of lanthanum-beta-aluminate (LBA) crystals formed in Ce-TZP matrix were studied by examining the crystal phase changes and the microstructures in relation to the heat-treatment time, heat-treatment temperatures and the particle size of raw Al2O3 powders. In the Ce-TZP matrix, the LBA crystal was formed by the reaction between La2O3 and Al2O3 through the LaAlO3 phase as the intermediate. La2Zr2O7 forms at 800-degrees-C and remains in the temperature range 800-1 500-degrees-C, and LaAlO3 forms between 1200 and 1400-degrees-C. The LaAlO3 reacts with Al2O3 to form LBA above 1500-degrees-C. The diffusion of La3+ through the La2Zr2O7 phase was faster than that of Al3+. The morphology of LBA crystals was dependent on the particle size of the starting raw Al2O3 particle. When submicrometre size Al2O3 (0.4 mum) particles were used as the starting particles, anisotropic, plate-like LBA crystals, about 1 0 mum long, were formed during heat treatments. On the other hand, Al2O3 of larger grain sizes (3.6, 1 0.3 mum) yield conglomerates of LBA crystals. The size of the conglomerates is similar to that of the raw Al2O3 particle. The dependence of the morphology of LBA on the particle size of Al2O3 can be attributable to the sintering process of the Ce-TZP matrix, leading to the control of the mechanical properties of Ce-TZP ceramics with LBA crystals.