Microstructure and microwave dielectric properties of Ni doped zinc borate ceramics for LTCC applications

Highlights: • The first principle calculation was performed to research the mechanism of the improvement of the sintering and dielectric properties of Zn₃B₂O₆ ceramic with Ni²⁺ substitution. The mechanism involved bond properties, electron density and formation energy. • The Zn1 site was the priority to be occupied by Ni²⁺, and the substitution happened in all the Zn tetrahedrons. The activation energy and densification window decreased slightly, and the sintering property was modified. The bond property and electron distribution of Zn tetrahedron changed. • Densification level and dielectric properties of the ZBO ceramic improved (ε_r = 6.9, Q×f = 91,000 GHz at 15 GHz, τ_f = −55.6 ppm/°C and relative density=97.1% at 900 °C). -- Abstract: A detailed study was performed using the density function theory to research the mechanism of the improvement of the sintering and dielectric properties of Ni²⁺ substituted Zn₃B₂O₆ ceramic. The mechanism involved bond properties, electron density and formation energy. The synthesis process is based on the solid-state reaction method and characterized via scanning electron microscopy, X-ray energy-dispersive spectroscopy, Raman spectrometry, network analysis, differential thermal analysis and thermo-mechanical analysis. The Zn1 site was the priority to be substituted by Ni²⁺, and the substitution happened in all the Zn tetrahedrons. The activation energy and densification window decreased slightly, and the sintering property was modified. The bond property and electron distribution around the tetrahedron with Ni²⁺ changed, and densification level and dielectric performance of the ZBO ceramic improved (ε_r = 6.9, Q×f = 91,000 GHz at 15 GHz, τ_f = −55.6 ppm/°C with high relative density (97.1%) at 900 °C).