Effects of oxygen vacancy on bond ionicity and microwave dielectric properties of YxCe1-xO2-0.5x (x=0-0.7) ceramics

Novel YxCe1-xO2-0.5x (x = 0-0.7) ceramics, designed by replacing Ce4+ with Y3+, were prepared using a conventional oxide reaction. The oxygen vacancies, measured by X-ray photoelectron spectroscopy and analyzed through the electronic structure calculated via the first-principles method, were employed to investigate the effective valence electron charge, which plays a decisive role in calculating bond ionicity using P-V-L theory. After the substitution of Y3+ ions, the effective valence electron charge of the Ce-O bond changed because of an increase in oxygen vacancies, ultimately leading to a decrease in the Ce/Y-O bond ionicity of the YxCe1-xO2-0.5x ceramics. For microwave dielectric properties, when the YxCe1-xO2-0.5x (x = 0-0.5) ceramics were in the pure phase, porosity-corrected permittivity and Q x f values depended on the bond ionicity, and the temperature coefficient of the resonance frequency was analyzed using the bond valence. When the YxCe1-xO2-0.5x (x = 0.6 and 0.7) ceramics were in multiple phases, the microwave dielectric properties were associated with the phase composition.