Zirconia nucleating agent on microstructural and electrical properties of a CaMgSi_2O_6 diopside glass-ceramic for microwave dielectrics

摘要

Addition of different amount of zirconia (ZrO_2) nucleating agent into MgO-CaO-SiO_2 system to enhance the quality factor (Q × f) of CaMgSi_2O_6 diopside glass-ceramic for low sintering temperature process (from 850 to 950 ℃) was carried out in this work. The microstructures, microwave dielectric properties and nucleating/growth mechanism of m-ZrO_2 added CaMgSi_2O_6 system were analyzed using transmission electron microscopy (TEM) and electrical property measurements. Experimental results demonstrate that a solid solution of an amorphous phase MgO-CaO-SiO_2 and ZrO_2 forms after melted at 1500 ℃. The t-ZrO_2 appears in the amorphous matrix first and then crystalline CaMgSi_2O_6 particle grows up at around the boundary of t-ZrO_2 after thermal treatment at 850 ℃ due to heterogeneous nucleating. Formation of t-ZrO_2 is attributed to diffusion of Ca~(2+) to stabilize the m-ZrO_2. The quality factor of CaMgSi_2O_6 was significantly enhanced by adding 3 wt.% m-ZrO_2, indicating that the ZrO_2 nucleating agent could enhance crystallization and therefore increase the quality factor.