Complex (Mg1/3Ta2/3)4+ ionic substitution on the phase structure and microwave dielectric properties of wolframite MgZr1-x(Mg1/3Ta2/3)xNb2O8 (0 ≤ x ≤ 0.08) ceramics

In this study, single-phase MgZr1-x(Mg1/3Ta2/3)(x)Nb2O8 (0 <= x <= 0.08) ceramics with monoclinic wolframite structure were synthesized by the traditional solid-state method. The influences of (Mg1/3Ta2/3)(4+) substitution for Zr4+ on phase composition, microstructure, packing fractions, bond valences, and the microwave dielectric properties of the ceramics were systematically investigated. According to the Rietveld refinement results, with the doping of (Mg1/3Ta2/3)(4+), the decline of unit cell volume led to the shift of the main peak in XRD pattern to a higher angle. Furthermore, the trend of the experimental dielectric constant kept in line with the theoretical dielectric constant calculated by the Shannon complex polarizability theory. With the introduction of (Mg1/3Ta2/3)(4+) ion, the Q x f values were greatly improved due to the increase of the packing fractions, but the porosity caused by excessive substitution deteriorates the quality factor. The increase of B-site bond valence explained the decline of tau(f). In particular, the MgZr1-x(Mg1/3Ta2/3)(x)Nb2O8 (x = 0.04) ceramics sintered at 1340 degrees C for 4 h exhibited optimal microwave dielectric properties of epsilon(r) = 25.42, Q x f = 65,950 GHz, and tau(f) = - 61.04 ppm/degrees C.

Automated summary

In this study, single-phase MgZr1-x(Mg1/3Ta2/3)(x)Nb2O8 ceramics with monoclinic wolframite structure were synthesized by the traditional solid-state method. The effects of (Mg1/3Ta2/3)(4+) substitution for Zr4+ on phase composition, microstructure, packing fractions, bond valences, and microwave dielectric properties were investigated comprehensively. The results showed that the introduction of (Mg1/3Ta2/3)(4+) ions led to improvements in Q x f values due to increased packing fractions, but excessive substitution resulted in increased porosity.