Zirconia nucleating agent on microstructural and electrical properties of a CaMgSi2O6 diopside glass–ceramic for microwave dielectrics

Addition of different amount of zirconia (ZrO2) nucleating agent into MgO–CaO–SiO2 system to enhance the quality factor (Q × f) of CaMgSi2O6 diopside glass–ceramic for low sintering temperature process (from 850 to 950 °C) was carried out in this work. The microstructures, microwave dielectric properties and nucleating/growth mechanism of m-ZrO2 added CaMgSi2O6 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–SiO2 and ZrO2 forms after melted at 1500 °C. The t-ZrO2 appears in the amorphous matrix first and then crystalline CaMgSi2O6 particle grows up at around the boundary of t-ZrO2 after thermal treatment at 850 °C due to heterogeneous nucleating. Formation of t-ZrO2 is attributed to diffusion of Ca2+ to stabilize the m-ZrO2. The quality factor of CaMgSi2O6 was significantly enhanced by adding 3 wt.% m-ZrO2, indicating that the ZrO2 nucleating agent could enhance crystallization and therefore increase the quality factor.