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

Abstract

A temperature stable low temperature co-fired ceramic (LTCC) was fabricated by the powder mixture of Li2ZnTi3O8 ceramic, TiO2 τf-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) Li2ZnTi3O8−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 (τf) to near-zero owing to the opposite τf value to other phases. And simultaneously dielectric constant (er) demonstrated gradually increase, whereas the quality factor (Q × f) decreased gradually. The composite with x = 2 had an optimal microwave dielectric properties with er = 25.3, Q × f = 32,800 GHz, and τf = − 0.54 ppm/°C. The corresponding fitting equations of er, Q × f and τf 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.