Synthesis of LiBGeO4 using compositional design and its dielectric behaviors at RF and microwave frequencies

Borates are promising candidates as dielectric substrate materials in low temperature cofired ceramics technology (LTCC) due to their relative low sintering temperatures and relative permittivities compared to their counterparts. However, synthesizing borates having single-phase is still challenging because of the volatility and hydrophilicity of boron resources. In this work, a compositional design was utilized to synthesize single-phase LiBGeO ₄ ceramics over a broad temperature range from 600 to 840 °C. Radio-frequency dielectric behaviours featured a strong temperature dependence, especially at high temperatures (>400 °C), which is related to the thermally activated polarizations. LiBGeO ₄ ceramic sintered at 820 °C has optimum microwave dielectric properties with the relative permittivity (ε _r) of 6.28, a quality factor (Q × f) of 21,620 GHz, and a temperature coefficient of resonance frequency (τ _f) of -88.7 ppm/ ^°C. LiBGeO ₄ also showed chemical inertness when cofired with silver (Ag), provided an evidence for its utilization in LTCC technology. Overall, this work provides a strategy for facile synthesis of phase pure borates, via the proposed two-step process to obtain stable boron resources.