Investigating on sintering mechanism and adjustable dielectric properties of BLMT glass/Li2Zn3Ti4O12 composites for LTCC applications

Abstract

A series of novel low temperature co-fired ceramics were fabricated in x BLMT-(100-x) Li2Zn3Ti4O12 (2.5 ≤ x ≤ 80 wt%) composites sintered at 900 °C. The sintering mechanism, phase composition, microstructure and dielectric properties of the composites were investigated. The results showed that the sintering mechanism of composites with <20 wt% BLMT glass could be attributed to non-reactive liquid-phase sintering and LaBO3 phase was crystallized from glass beside Li2Zn3Ti4O12 phase, while composites with ≥20 wt% glass were controlled by the coexistence of viscous sintering and reactive liquid-phase sintering, BLMT glass crystallized forming LaBO3, MgLaB5O10 and a small amount of rutile phase, nevertheless, more rutile phase was formed by reacting between glass and ceramic. As BLMT glass was increased, LaBO3, MgLaB5O10 and rutile phase gradually dominated the material and Li2Zn3Ti4O12 phase decreased. Meanwhile, the dielectric constant (εr) and quality factor (Q × f) demonstrated gradually decrease, whereas the temperature coefficient of resonant frequency (τf) presented a trend of fall first then rise. Typically, the composite with 60 wt% glass displayed excellent dielectric properties with εr = 14, Q × f = 23,000 GHz, and τf = −3.56 ppm/°C. The corresponding fitting equations of εr, Q × f and τf on the BLMT glass content were obtained by the Origin software, which indicated that the dielectric properties of BLMT/Li2Zn3Ti4O12 composites could be precisely adjusted by adding the suitable content of glass. Therefore, the sintering process, phase composition and dielectric properties of BLMT/Li2Zn3Ti4O12 composites can be controlled by varying the content of Li2Zn3Ti4O12 ceramic and B2O3-La2O3-MgO-TiO2 glass.