Dielectric mechanism and chemical bond characteristics of BaZn1-xCuxP2O7 ceramics in MW/THz frequency bands
To explore high-performance dielectric ceramics with intrinsically low sintering temperatures and low permittivity suitable for use in the microwave (MW) and terahertz (THz) ranges, Cu ions were selected to replace Zn ions in BaZnP 2 O 7 ceramics based on the considerations of ionic radius and chemical bond characteristics. Samples with moderate Cu 2+ substitution exhibited better performance than conventional ones, with a similar dielectric mechanism in both MW and THz frequency ranges. All samples of BaZn 1- x Cu x P 2 O 7 (0 ≤ x ≤ 0.1) solid solutions exhibit a single-phase with a triclinic structure ( P-1 ) when the sintering temperature is below 925 °C, while the BaCuP 2 O 7 phases form in the doped samples at 925 °C. Cu 2+ substitution improves density and enhances molecular polarizabilities and average ionicity, thereby raising the dielectric constant ε r . The substitution of Cu 2+ for Zn 2+ in BaZnP 2 O 7 ceramics shortens the chemical bonds, thus improving lattice stability and reducing the damping factor of phonon anharmonic vibrations. This, in turn, increases the Q × f values by 1.65 times and enhances temperature stability compared to conventional ceramics. The BaZn 1- x Cu x P 2 O 7 ceramics have good chemical compatibility with Cu, but react with Ag.
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