Effects of Ta5+ substitution on mechanical and microwave dielectric properties of R(Nb1-xTax)2O6 ceramics

Microwave dielectric ceramics (MWDCs) are prone to mechanical failure, and improving the mechanical properties of MWDCs is of significance for their application under extreme conditions. Novel high-entropy R(Nb 1- x Ta x ) 2 O 6 (R = Mg 0.2 Mn 0.2 Co 0.2 Ni 0.2 Zn 0.2 ) ceramics were prepared by the solid-phase reaction method. The single-phase and composite solid solutions of the R(Nb 1- x Ta x ) 2 O 6 series were successfully prepared, as evidenced by XRD, Raman spectra, and combined with EDS energy spectrum analysis. The average grain size was found to increase with the Ta 5+ content, while the grain dispersion exhibited a trend of increasing and then decreasing, resulting in a trend of increasing and then decreasing Q× f . The replacement of Nb 5+ by Ta 5+ has been demonstrated to improve τ f and enhance the mechanical properties. An increase in Ta 5+ content from 0.5 to 0.75 results in a significant enhancement in ε r and mechanical properties, which is primarily attributed to the generation of the RTa 2 O 6 phase. When x = 1, the R(Nb 1- x Ta x ) 2 O 6 ceramics exhibit excellent microwave dielectric properties (ε r = 31.28, Q× f = 20,722, τ f = 48.36) and the most favorable mechanical properties ( H v = 7.99 GPa, σ = 882 MPa, TRS = 237.7 MPa). This study provides a new idea to improve the mechanical properties of MWDCs.