Structural and electrical characterization of CeAlO[sub 3] ceramics

The crystal structure and electrical properties of CeAlO3 ceramics prepared by the mixed oxide route have been investigated. X-ray and electron diffraction data show the room temperature structure to be described by the tetragonal I4/mcm space group [a = 5.3253(5) Å and c = 7.5860(9) Å; Z = 4, and theoretical density, Dx = 6.64 g/cm3]. CeAlO3 ceramics sintered at 1500 °C under flowing 5%H2–95%N2 gas for 4 h reach ∼ 94% of Dx with a microstructure of randomly distributed equiaxed grains of average grain size ∼ 2 μm. Conventional transmission electron microscopy reveals needle-shaped ferroelastic domains in some grains. The relative permittivity εr of CeAlO3 ceramics is ∼ 18–20 in the range of ∼ 10–300 K. At room temperature and microwave frequencies, CeAlO3 ceramics exhibit εr ∼ 20.7, Qfr ∼ 40 117 GHz (at 9.5 GHz), and τf ∼ −57 ppm/K. The ion polarizability for Ce3+ is calculated to be 4.46 Å3. Revised dielectric polarizabilities for rare-earth lanthanides are also presented.