Enhanced microwave dielectric properties of Bi6B10O24 ceramics as ultra-low temperature co-fired ceramics materials

The Bi6B10O24 microwave dielectric ceramics for ultra-low temperature co-fired ceramics application were prepared by solid-state reaction method. The process conditions, phase composition, and microwave dielectric properties of the ceramics were investigated. The results indicated that boron volatilization was effectively avoided by dry ball milling of the raw materials and calcined in sealed environment for the powder preparation and then a single Bi6B10O24 phase ceramic was successfully obtained. The Bi6B10O24 ceramics exhibited microwave dielectric properties: εr = 13.2 ± 0.1, Q × f = 25,000 ± 200 GHz, and τf =  − 65 ± 2 ppm/°C. The effect of small excess B2O3 on the phase, microstructure, and microwave dielectric properties on the Bi6B10O24 ceramics were discussed. Bi6B10O24–xB2O3 ceramics (x = 0–0.12 mol%) were sintered at 670–710 °C for 2 h. The XRD patterns of specimens illustrated that only the Bi6B10O24 phase was observed for all the ceramics with varying x. The microwave dielectric properties of the ceramics were found to strongly correlate with the x values and sintering process. The appropriate excess B2O3 is beneficial to densification of the ceramics, effectively reducing the dielectric loss and increasing Q × f. The excellent microwave dielectric properties of the Bi6B10O24 ceramics were obtained for x = 0.1 mol, εr = 12.5 ± 0.1, Q × f = 38,200 ± 300 GHz, and τf =  − 62 ± 1 ppm/°C. The high-performance Bi6B10O24 ceramics are promising candidates for ULTCC integration applications.