Temperature stable microwave dielectric ceramics in Li₂ZnTi₃O₈–based composite for LTCC applications

A temperature stable low temperature co-fired ceramic (LTCC) was fabricated by the powder mixture of Li₂ZnTi₃O₈ ceramic, TiO₂ τ_f-tailoring dopant and B₂O₃–La₂O₃–MgO–TiO₂ (BLMT) glass sintering aid, and the sintering behavior, activation energy, phase composition, microstructure and microwave dielectric properties of the composite were investigated in the composition range (wt%) of 5 BLMT–(95-x) Li₂ZnTi₃O_8−X TiO₂ (x = 0, 1, 2, 3, 4 and 5). The sintering behavior results showed that all composites could be well sintered at 910 °C for 2 h through liquid-phase sintering. The activation energy of Li₂ZnTi₃O₈ ceramic was calculated to be 520.9 ± 40.46 kJ/mol, while 5BLMT–93Li₂ZnTi₃O₈–2TiO₂ (in wt%) composite was reduced to 330.98 ± 47.34 kJ/mol. The XRD results showed that Li₂ZnTi₃O₈ and TiO₂ phase stably existed in all sample and a new phase LaBO₃ was crystallized from BLMT glass during sintering process. As x increases, the rutile TiO₂ phase increased in composite, which could adjust the temperature coefficient of resonant frequency (τ_f) to near-zero owing to the opposite τ_f value to other phases. And simultaneously dielectric constant (ε_r) demonstrated gradually increase, whereas the quality factor (Q × f) decreased gradually. The composite with x = 2 had an optimal microwave dielectric properties with ε_r = 25.3, Q × f = 32,800 GHz, and τ_f = − 0.54 ppm/°C. The corresponding fitting equations of ε_r, Q × f and τ_f on the x value were obtained by the Origin software, indicating that the dielectric properties of the composite could be precisely controlled by varying the content of TiO₂. In addition, the good chemical compatibility of this material with Ag electrode made it as a potential candidate for LTCC technology.