Effects of oxygen vacancy on bond ionicity, lattice energy, and microwave dielectric properties of CeO 2 ceramics with Yb 3+ substitution

Novel Yb_xCe_1-xO_2-0.5x (x=0-0.8) ceramics, designed by replacing Ce⁴⁺ with Yb³⁺ ions were prepared by conventional oxide reaction, and the structural stability of the cubic fluorite structure was assessed using lattice energy and the ionic properties of Ce/Yb-O bonds. The oxygen vacancy caused by unequal substitution, which played a decisive role on bond ionicity and lattice energy, was analyzed experimentally by XPS and also theoretically by first principles. The Yb_xCe_1-xO_2-0.5x ceramics maintain a stable cubic fluorite structure when x£0.47, corresponding to the minimum lattice energy of 4142kJ/mol with the lowest ionicity as ¦_i=87.57%. For microwave dielectric properties, when Yb_xCe_1-xO_2-0.5x (x=0-0.4) ceramics are pure phase, the porosity-corrected permittivity is depended on the bond ionicity. The Q´¦ values are related to the lattice energy and grain distribution. The temperature coefficient of resonance frequency has been analyzed using bond valence. When Yb_xCe_1-xO_2-0.5x (x=0.5-0.8) ceramics are multiple phase, the microwave dielectric properties are associated with the phase composition and grain growth.