Effect of addition of strontium on the structure and microwave dielectric properties of BaNi₂V₂O₈ ceramics

Ba_1-xSr_xNi₂V₂O₈ (x = 0, 0.05, 0.1, 0.15) ceramics were fabricated utilizing the solid-state reaction methods. The XRD and structural refinement results demonstrated an increased presence of a new Ba_0.5Sr_0.5Ni₂V₂O₈ phase with higher Sr²⁺ content. With a distinctive tetragonal structure, this new phase markedly differed from the hexagonal structure of BaNi₂V₂O₈. Our analyses of molecular polarization, packing fraction, and distortion of the [NiO₆] octahedra revealed that the ε_r and τ_f of Ba_0.5Sr_0.5Ni₂V₂O₈ surpassed those of BaNi₂V₂O₈, while its Q × f value was lower. This explains the amplified ε_r and τ_f value, alongside the diminished Q × f value of the ceramics. The introduction of Sr²⁺ elevated the τ_f value of the ceramics from − 49.5 ppm/°C to − 7.8 ppm/°C. The Ba_0.85Sr_0.15Ni₂V₂O₈ specimen, sintered at 950 °C for 4 h, exhibited the most superior microwave dielectric performance: ε_r = 12.7, Q × f = 34,200 GHz, τ_f =  − 7.8 ppm/°C. These outcomes underscore the promising practical potential of this ceramic.