Influence of Al_2O_3/SiO_2 ratio on the microstructure and properties of low temperature co-fired CaO-Al_2O_3-SiO_2 based ceramics

摘要

In this work, in order to obtain the materials for low temperature co-fired ceramics applications, CaO-Al_2O_3-SiO_2 (CAS) based ceramics were synthesized at a low sintering temperature of 900 ℃. The influences of Al_2O_3/ SiO_2 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 Al_2O_3 is advantageous for the formation of the desired materials. Anorthite(CaAl_2Si_2O_8) is the major crystal phase of the ceramics, and the SiO_2 phase is identified as the secondary crystal phase. No new crystal phase appears in the ceramics with the increasing Al_2O_3 content. More or less Al_2O_3 addition would all worsen the sintering, mechanical and dielectric properties of CAS based ceramics. The ceramic specimen (Al_2O_3/SiO_2 = 20/18.5) sintered at 900 ℃ 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.