Addition of different amount of zirconia (ZrO ) nucleating agent into MgO-CaO-SiO system to enhance the quality factor (Q × f) of CaMgSi O 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-ZrO added CaMgSi O 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 and ZrO forms after melted at 1500 °C. The t-ZrO appears in the amorphous matrix first and then crystalline CaMgSi O particle grows up at around the boundary of t-ZrO after thermal treatment at 850 °C due to heterogeneous nucleating. Formation of t-ZrO is attributed to diffusion of Ca to stabilize the m-ZrO . The quality factor of CaMgSi O was significantly enhanced by adding 3 wt.% m-ZrO , indicating that the ZrO nucleating agent could enhance crystallization and therefore increase the quality factor. © 2012 Elsevier Ltd. All rights reserved.