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

Addition of different amount of zirconia (ZrO{sub 2}) nucleating agent into MgO–CaO–SiO{sub 2} system to enhance the quality factor (Q × f) of CaMgSi{sub 2}O{sub 6} 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{sub 2} added CaMgSi{sub 2}O{sub 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{sub 2} and ZrO{sub 2} forms after melted at 1500 °C. The t-ZrO{sub 2} appears in the amorphous matrix first and then crystalline CaMgSi{sub 2}O{sub 6} particle grows up at around the boundary of t-ZrO{sub 2} after thermal treatment at 850 °C due to heterogeneous nucleating. Formation of t-ZrO{sub 2} is attributed to diffusion of Ca{sup 2+} to stabilize the m-ZrO{sub 2}. The quality factor of CaMgSi{sub 2}O{sub 6} was significantly enhanced by adding 3 wt.% m-ZrO{sub 2}, indicating that the ZrO{sub 2} nucleating agent could enhance crystallization and therefore increase the quality factor.