Ultralow Loss CaMgGeO₄ Microwave Dielectric Ceramic and Its Chemical Compatibility with Silver Electrodes for Low-Temperature Cofired Ceramic Applications

Abstract

A new ultralow dielectric loss cofired CaMgGeO4 dielectric material with olivine structure was fabricated by the solid-state route. The X-ray patterns, Rietveld refinement, and microstructure revealed the characteristics of the synthesized material. CaMgGeO4 ceramic belongs to the orthorhombic system with a Pbmn space group. Sintered at 1300 °C for 6 h, the ceramic exhibited a densification of 96.5%, an ultrahigh quality factor (Q × f) of 124 900 GHz (tan δ = 1.24 × 10–4) at a frequency of 15.5 GHz, a permittivity (εr) of 6.71, and a temperature coefficient of resonant frequency (τf) of −73.7 ppm/°C, and the average coefficient of thermal expansion of CaMgGeO4 was 12.4 ppm/°C. The sintering temperature of the CaMgGeO4 ceramic was reduced from 1300 to 940 °C with the addition of 5 wt % B2O3. The CaMgGeO4 + 5 wt % B2O3 ceramics exhibited favorable microwave dielectric performances: Q × f = 102 000 GHz (at 16.4 GHz), εr = 5.80, and τf = −64.7 ppm/°C, respectively. In addition, the CaMgGeO4 ceramic did not react with Ag electrodes, which could be advantageous in low-temperature cofired ceramic multilayer microwave devices.

Ultra‐low fired fluoride composite microwave dielectric ceramics and their application for BaCuSi2O6‐based LTCC

“…4,5 More importantly, these materials should not react with Ag electrodes and the sintering temperature should be lower than 961°C. 6 Adding a sintering aid is an efficient method to reduce the sintering temperature. The most commonly used glass for LTCC is the borate glass, such as BaCu(B 2 O 5 ), ZnO-B 2 O 3 , and La 2 O 3 -CaO-B 2 O 3 types of glass.…”

“…LTCC for millimeter‐wave devices must have a low ε r , a high Q × f , and a near zero τ f . More importantly, these materials should not react with Ag electrodes and the sintering temperature should be lower than 961°C …”

Crystal structure, dielectric properties, and lattice vibrational characteristics of LiNiPO4ceramics sintered at different temperatures

“…Owing to the wide application of microwave communication, it is necessary to investigate new technologies for the integration and miniaturization of microwave devices . Among these technologies, low‐temperature co‐fired ceramics (LTCCs) are widely used to manufacture high‐mount‐density, low‐loss modules for high‐performance electronic systems owing to their excellent electronic, mechanical, and thermal properties . The selection of materials is critical and determines the ultimate performance of the module.…”

“…1,2 Among these technologies, low-temperature co-fired ceramics (LTCCs) are widely used to manufacture high-mount-density, low-loss modules for high-performance electronic systems owing to their excellent electronic, mechanical, and thermal properties. 3,4 The selection of materials is critical and determines the ultimate performance of the module. During the production of LTCCs, the densification temperature should be lower than the melting point of the Ag or Cu electrode material (eg, 961°C for Ag).…”

Ultralow temperature cofired BiZn2VO6 dielectric ceramics doped with B2O3 and Li2CO3 for ULTCC applications

“…Microwave dielectrics ideally need to be sintered at low temperature for energy saving as well as for the improvement of their cofiring compatibility with cost‐effective metallic electrodes . In order to address this issue, low temperature cofired ceramics (LTCC) technology has been developed for the manufacture of miniaturized, lightweight and integrated electronic components, modules, substrates, and devices . The microwave dielectrics fabricated through the LTCC route have suitable relative permittivity (ε r ) (high for miniaturization and low for fast signal transmission), high quality factor ( Q × f , >5000 GHz), a quasi‐zero temperature coefficient of resonant frequency (−10 ppm/°C ≤ τ f ≤ +10 ppm/°C to guarantee temperature stability) and a sintering temperature below 1000°C (compatible with Ag, Au, Cu, and their alloys as electrodes) .…”