Defect Analysis in CaMgSi_2O_6 Glass-ceramic under Reduction Atmosphere

摘要

The co-firing process of base-metal-electrode (Cu) and glass-ceramic system in reducing atmosphere used for preparing microwave dielectric materials were studied for low temperature co-fired ceramic (LTCC) capacitors in the present work. In order to clarify reducing characteristics of pertinent materials, the defect analysis and dielectric properties of MgOCaO-2SiO_2-ZrO_2 glass-ceramics, sintered in different atmosphere, were investigated using x-ray diffractometry (XRD), x-ray photoelectron spectroscopy (XPS), and microwave dielectric measurement in this work. Experimental results demonstrate that peaks in x-ray diffraction show serious peak broadening, indicating that the specimens sintered in N_2/H_2 atmosphere exhibit high internal strain (ε≈ 0.00714 ± 0.05%) in the lattice. This may be attributed to the lattice distortion caused by formation of oxygen vacancy and clusters. Furthermore, it is found that most the silicon species exhibited as Si~(4+) primarily for specimens sintered in air. On the other hand, reduction of Si~(4+) to Si~(3+) and Si~(4+) to Si~(2+) happens in the specimens sintered in N_2 and mixed N_2/H_2 atmospheres. XPS study reveals that hydrogenation leads to an increase in the amount of oxygen vacancies to form the charge exchange mechanism in these sintered samples. Therefore, degradation of the quality factors and increasing of current densities occur in specimens under a reduced atmosphere, indicating that hydrogenation-resistance of MgO-CaO-2SiO_2-ZrO_2 based dielectrics in a sintering process needs to be improved.