Developing high-Q × f value MgNb2–xTaxO6(0≤x≤0.8) columbite ceramics and clarifying the impact mechanism of dielectric loss: Crystal structure, Raman vibrations, microstructure, lattice defects, chemical bond characteristics, structural parameters, and microwave dielectric properties in-depth studies

•A strategy to optimize the bond characteristics by introducing Ta5+ is proposed.•Structural properties on MgNb2−xTaxO6 (0 ≤ x ≤ 0.8) solid solutions are clarified.•Considerably enhanced Q × f (∼ 170,000 GHz) is achieved when x = 0.6.•The theory associated with low dielectric loss of MgNb2O6 system is enriched.