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The feasibility of novel LiCo 1-x A x VO 4 (A = Mg, Zn; x = 0-0.09) microwave dielectrics for ULTCC (ultra-low temperature co-fired ceramics) applications was investigated. Continuous solid solutions were formed as expected in the whole composition range and can be indexed in the cubic system with the Fd3m space group. The Raman spectrum of the specimen was also analyzed. All samples can be sintered into dense ceramics (relative density> 97%) at the temperature 650°C. The variation of structure parameters resulted from minutely substituting Co with Mg or Zn has significant effect on the microwave dielectric properties of the specimen. The relative density and dielectric polarizability have significant impact on the ɛ r of the specimens. Q × f value is dominated by the density and packing fraction of the ceramics. The τ f , however, was mainly controlled by the bond-valence of the samples under a minute substitution. Specimen with 0.01 mol% Zn-substitution at 650°C revealed the highest Q × f of 53,000 GHz along with an ε r of 13.2 and a τ f of -57.5 ppm/°C. It also exhibited a good Alcofiring chemical compatibility.

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