Influence of Al2O3/SiO2 ratio on the microstructure and properties of low temperature co-fired CaO–Al2O3–SiO2 based ceramics

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In this work, in order to obtain the materials for low temperature co-fired ceramics applications, CaO–Al2O3–SiO2 (CAS) based ceramics were synthesized at a low sintering temperature of 900 °C. The influences of Al2O3/SiO2 ratio on the microstructure, mechanical, electrical and thermal properties were studied. According to the X-ray diffractomer and scanning electron microscopy results, the addition of the Al2O3 is advantageous for the formation of the desired materials. Anorthite(CaAl2Si2O8) is the major crystal phase of the ceramics, and the SiO2 phase is identified as the secondary crystal phase. No new crystal phase appears in the ceramics with the increasing Al2O3 content. More or less Al2O3 addition would all worsen the sintering, mechanical and dielectric properties of CAS based ceramics. The ceramic specimen (Al2O3/SiO2 = 20/18.5) sintered at 900 °C shows good properties: high bending strength = 145 MPa, low dielectric constant = 5.8, low dielectric loss = 1.3 × 10−3 and low coefficient of thermal expansion value = 5.3 × 10−6 K−1. The results indicate that the prepared CAS based ceramic is one of the candidates for low temperature co-fired ceramic applications.