V2O5-Assisted Low-Temperature Sintering and Microwave Dielectric Properties of (1-x)Li2.08TiO3-xLi2ZnTi3O8 (x=0.3-0.7) Ceramics for LTCC Applications

초록

A new composite microwave-dielectric system, (1 - x)Li2.08TiO3-xLi(2)ZnTi(3)O(8) (x = 0.3-0.7), was systematically investigated to identify the optimal composition for low-temperature co-fired ceramic (LTCC) applications by correlating sintering behavior, microstructural evolution, and microwave-dielectric properties. Although the undoped compositions exhibited excellent intrinsic dielectric performance, they required sintering at 1100 degrees C, making them incompatible with Ag-based LTCC processing. Among the investigated formulations, 0.6Li(2.08)TiO(3)-0.4Li(2)ZnTi(3)O(8) was identified as the most suitable base composition. To reduce the sintering temperature, 0.3-1.0 wt.% V2O5 was introduced as a sintering aid, enabling densification at 900 degrees C for 30 min (97.0% relative density) while preserving the coexistence of Li2.08TiO3 and Li2ZnTi3O8 without XRD-detectable secondary phases. Microstructural observations indicated that V2O5 promoted liquid-phase sintering, leading to enhanced densification and Li2.08TiO3-selective abnormal grain coarsening without altering the intrinsic permittivity. Complementary dilatometry provided process-level evidence for this liquid-phase sintering mechanism: large total shrinkage at 900 degrees C (Delta L/L-o approximate to -17-19%), earlier T-onset/T-peak with T-peak lowered by similar to 250 degrees C, and an increased R-peak, collectively supporting 900 degrees C/30 min as the practical firing window. The optimized 0.6Li(2.08)TiO(3)-0.4Li(2)ZnTi(3)O(8) composition containing 0.3 wt.% V2O5 exhibits excellent microwave-dielectric properties (epsilon(r) = 23.32, Q x f = 68,400 GHz, and tau(f)= -1.55 ppm/degrees C). Higher V2O5 contents (>0.3 wt.%) caused a gradual reduction in Q x f due to increasing microstructural non-uniformity. Ag co-firing tests confirmed electrode stability with no interfacial reactions at 900 degrees C for 30 min. Overall, 0.3 wt.% V2O5-assisted 0.6Li(2.08)TiO(3)-0.4Li(2)ZnTi(3)O(8) provides a practical sub-950 degrees C processing window that satisfies key LTCC requirements, including moderate permittivity, high Q x f, near-zero tau(f), and compatibility with Ag electrodes.

키워드