The effects of CaO–B2O3–SiO2 (CBS) glass addition on the sintering temperature and dielectric properties of Li2ZnTi3O8–TiO2 (LZT) composite ceramics have been investigated. Due to the compensating effect of rutile TiO2 (τf ≈ +450 ppm/ °C), the temperature coefficient of resonant frequency (τf) for Li2ZnTi3O8 + 4 wt% TiO2 with biphasic structure was adjusted to a value near zero. The pure LZT ceramics were usually sintered at high temperature of about 1,160 °C. It was found in our experiment that a small amount of CBS glass additives could effectively lower the sintering temperature of LZT ceramics to 900 °C. With increasing the content of CBS glass, both of dielectric constant (er) and quality factor (Q × f) value decreased. Typically, the 1 wt% CBS glass added Li2ZnTi3O8 + 4 wt% TiO2 ceramic sintered at 900 °C for 4 h exhibited good microwave dielectric properties of er = 26.9, Q × f = 23,563 GHz and τf = −1.5 ppm/ °C, which made it promising for low temperature co-fired ceramics technology application.

Low temperature sintering and dielectric properties of Li2ZnTi3O8–TiO2 composite ceramics doped with CaO–B2O3–SiO2 glass

The novel low-temperature sinterable ceramic composites were fabricated by mixing B2O3-La2O3-MgO-TiO2 (BLMT) glass with Li2ZnTi3O8 ceramic. All composites could be well sintered at 900 °C for 2 h through liquid-phase sintering and viscous sintering process. With BLMT glass increasing, the main phase of composites changed from Li2ZnTi3O8 to LaBO3 phase crystallized from glass. Nevertheless, the rutile phase was observed in composites with ≥10 wt% glass, which could adjust the temperature coefficient of resonant frequency (τf) to near-zero owing to the opposite τf value to other phases. Simultaneously relative permittivity (er) and quality factor (Q × f) could be controlled by varying the content of Li2ZnTi3O8 ceramic and BLMT glass. The composite with 20 wt% glass exhibited excellent dielectric properties: er = 22.7, Q × f = 19,900 GHz, and τf  = 0.28 ppm/°C. In addition, the good chemical compatibility between the composite with 5 wt% glass and Ag electrode made it as a potential candidate for LTCC technology.

Investigation on low-temperature sinterable behavior and tunable dielectric properties of BLMT glass-Li2ZnTi3O8 composite ceramics

A new series of LTCC compositions having the general formula Bi3.9RE0.1(SiO4)3 where, (RE = Yb, Tm, Er, Gd, Sm, Nd, Pr) were developed. The crystal structure analysis using Rietveld refinement of the powder diffraction data of all compositions confirmed partial substitution of rare earth at bismuth site. The microwave dielectric and thermal properties of these new LTCC compositions were studied. Some of the rare earth substituted compound namely, Bi3.9Tm0.1(SiO4)3, Bi3.9Sm0.1(SiO4)3, show improvement in Qu × f value (22,600 GHz and 24,100 GHz respectively at 8.2 GHz) as compared to the parent Bi4(SiO4)3 (20,500 GHz, at 8.2 GHz).

Structural, thermal and dielectric properties of rare earth substituted eulytite for LTCC applications

The effects of Li2O–ZnO–B2O3 (LZB) glass additive on the sintering behavior, phase composition, microstructure and microwave dielectric properties of Li2TiO3 (LT) ceramics have been investigated. The addition of a small amount of LZB glass can reduce the sintering temperature of LT ceramics from 1150 °C to 900 °C without obvious degradation of the microwave dielectric properties. Only a single-phase Li2TiO3 is formed in LT ceramic with LZB glass addition sintered at 900 °C for 2 h. Typically, the 2.5 wt% LZB glass-added LT ceramic sintered at 900 °C for 2 h can reach a maximum relative density of 94.8% of the theoretical density and exhibits good microwave dielectric properties of e r =22.9, Q f =59,600 GHz and τ f =+23.7 ppm/°C. The XRD, SEM and EDX analyses showed that the ceramic can be co-fired well with Ag electrode, which may be applied for LTCC application.

Microwave dielectric properties and chemical compatibility with silver electrode of Li2TiO3 ceramic with Li2O–ZnO–B2O3 glass additive

Synthesis and characterization of high-density B2O3-added forsterite ceramics

The effect of B2O3 addition on the microwave dielectric properties and microstructure of Li2ZnTi3O8 ceramics prepared using conventional solid-state reaction was investigated for low-temperature co-fired ceramic (LTCC) applications. X-ray diffraction and scanning electron microscopy were used to investigate the effect of B2O3 addition on the sintering process. The Li2ZnTi3O8 ceramic sintered at 875°C with 0.5 wt% B2O3 for 4 h showed good microwave dielectric properties including er = 25, Q × f = 50,917 GHz, and τf = −17.8 ppm/°C. Silver was found to be unreactive toward the 0.5 wt% B2O3 doped Li2ZnTi3O8 ceramic under the above sintering conditions.

Bing-Guang Tsai

Papers

Influence of B2O3 Additive on Microwave Dielectric Properties of Li2ZnTi3O8 Ceramics for LTCC Applications