(Co1/3Ni1/3Zn1/3)2+-substituted MgTa2O6 microwave dielectric ceramics with Qf value stability across a broad sintering temperature range

Mg 1–3 x (CoNiZn) x Ta 2 O 6 ceramics ( x = 0.00, 0.05, 0.10, 0.20, and 0.25) were synthesized by the solid-phase reaction method. The XRD and Rietveld refinement results suggest that the Mg 1–3 x (CoNiZn) x Ta 2 O 6 ceramics have a pure tri-rutile structure. (Co 1/3 Ni 1/3 Zn 1/3 ) 2+ can significantly broaden the sintering temperature range of ceramics. The chemical bonding theory reveals that the A-O bond (A = Mg, Co, Ni, or Zn) ionicity and Ta-O bond ionicity are closely related to the porosity corrected relative permittivity ( ε r -corr. ). The increase in A-O bond energy contributes to the greater stability of the AO 6 octahedron , resulting in a decrease in | τ f |. Additionally, the Raman spectroscopy reveals that there is a negative relationship between the Qf value and the full width at half maximum ( FWHM ) of the strongest peak of the A 1g mode. Correspondingly, Mg 0.4 (CoNiZn) 0.2 Ta 2 O 6 ceramic has excellent microwave dielectric properties after sintering at 1450°C for 4 h: ε r = 28.9, Qf = 91,900 GHz (at 7.4 GHz), and τ f = 44 ppm/°C. Furthermore, Mg 0.4 (CoNiZn) 0.2 Ta 2 O 6 ceramic can maintain a stable Qf value (∼ 91,000 GHz) across a broad range of sintering temperatures (150°C), which is a result of the combination of densification and FWHM . This characteristic facilitates adaptation to changes in furnace temperature in large-scale production. The strategy of multiple-element substitution to extend the sintering temperature range is expected to be applied to other ceramic systems.