Enhanced quality factor (∼336,800 GHz) of MgTiO3 ceramic by Hf substitution for Ti-site.

Mg(Ti 1– x Hf x)O 3 (0 ≤ x ≤ 0.1) microwave dielectric ceramics were synthesized by solid-state reaction method. The effects of Hf substitution for the Ti-site on the phase composition, structure, and microwave dielectric properties of MgTiO 3 ceramic were systematically investigated. The study demonstrated that Hf substitution significantly improved the quality factor of MgTiO 3 ceramic. A single phase was confirmed at x = 0.002 and 0.005 by XRD and SEM, while secondary phases were observed at x ≥ 0.02. The Rietveld refinement of XRD data implied that the distortion of [Ti(Hf)O 6 ] octahedron started with alleviation and then gradually deteriorated with an increase in Hf content. Raman spectra displayed that the frequencies of the vibrational modes were high when there was low distortion in [Ti(Hf)O 6 ] octahedron, manifesting that the low distortion weakened the effect of non-harmonic vibration. The quality factor of the samples with x ≤ 0.05 was far higher than that of undoped MgTiO 3 , which may be related to low distortion in [Ti(Hf)O 6 ] octahedron and high relative density. Notably, the excellent microwave dielectric properties of Q × f ∼336,829 GHz, ε r ∼17.2 and τ f ∼ - 49.7 ppm/°C were achieved for the Mg(Ti 0.995 Hf 0.005)O 3 ceramic. The greatly improved quality factor of MgTiO 3 -based microwave ceramics through Hf substitution makes it a suitable candidate material for ceramic filters. [ABSTRACT FROM AUTHOR]