Room-temperature-densified H3BO3 microwave dielectric ceramics with ultra-low permittivity and ultra-high Qf value

Abstract

With the rapid development of mobile communication technology towards 5G and 6G, the microwave dielectric materials with ultra-low permittivity and ultra-high Qf value are urgently demanded. Here, the excellent microwave dielectric properties are reported in H3BO3 ceramics with the molecular crystal structure, whose permittivity (2.84) and density (1.46 g/cm3) are record-low among the low-loss ceramics. The ultra-high Qf value of 146,000 GHz (or the ultra-low dielectric loss of 1.03 × 10−4 at 15 GHz) is also distinguished. Besides, the H3BO3 ceramics can be densified at room temperature by a simple cold sintering process in a short time of 10 min, and this brings many advantages for the integration with microwave circuits. The large molecule volume originating from the molecular crystal structure and the low dielectric polarizabilities of H+ and B3+ are responsible for the ultra-low permittivity of H3BO3 ceramics, and more microwave dielectric materials with ultra-low permittivity and ultra-high Qf value are expected to be explored in the molecular crystals. Keywords: Boric acid, Microwave dielectric ceramics, Room-temperature cold sintering, Ultra-low permittivity