A comprehensive study on low-temperature sintering and microwave/terahertz dielectric properties of BaO-P₂O₅ binary ceramics

In this study, the sintering characteristics, microstructure, phase composition, crystal structure, dielectric properties, and thermal properties of ceramic samples in the BaO-P₂O₅ binary system were comprehensively investigated. Furthermore, the intrinsic dielectric properties of ceramic samples in the BaO-P₂O₅ binary system were elucidated through the analysis of Fourier transform infrared (FTIR) reflectance spectra and terahertz time-domain spectra (THz-TDS). The experimental results showed that BaP₂O₆ ceramics exhibited good microwave dielectric properties after sintering at 800 °C for 2 h: permittivity (ϵ_r) = 6.3, quality factor (Q × f) = 17 100 GHz (@12.75 GHz), and τ_f (TCF, temperature coefficient of resonant frequency) = −45 ppm °C⁻¹. Ba₃P₂O₈ + 2 wt% BCB ceramics exhibited excellent microwave dielectric properties after sintering at 800 °C for 2 h: ϵ_r = 10.1, Q × f = 75 000 GHz (@11.05 GHz), and τ_f = +9 ppm °C⁻¹. Moreover, they showed good chemical compatibility with Ag and Cu electrodes. A cylindrical dielectric resonant antenna (DRA) element was designed based on Ba₃P₂O₈ + 2 wt% BCB ceramics, and a 1 × 4 line array was designed based on the unit antenna model. The 1 × 4 DRA line array exhibited a high radiation efficiency of 95%, accompanied by a realized gain of 9.5 dBi. The utilization of Ba₃P₂O₈ + 2 wt% BCB ceramics is anticipated for 5.8 GHz Wi-Fi communication. This study presents a comprehensive theoretical framework and technical guidance for developing ceramics in the BaO-P₂O₅ binary system.