Dual effect of ZrO2 on phase separation and crystallization in Li2O–Al2O3–SiO2–P2O5 glasses

Abstract ZrO 2 is an effective nucleation agent for low‐expansion lithium–aluminum silicate (LAS) glass–ceramic (GC) with high Al 2 O 3 content. However, the effect of ZrO 2 is still not fully understood in LAS glasses with low contents of Al 2 O 3 and P 2 O 5 . In this work, the effect of ZrO 2 on the phase separation and crystallization of Li 2 O–Al 2 O 3 –SiO 2 –P 2 O 5 glasses were investigated. The results revealed that ZrO 2 significantly increased T g and the crystallization temperature of Li 2 SiO 3 and Li 2 Si 2 O 5 crystals. Li 3 PO 4 crystals precipitated preferentially in the glass containing 3.6‐mol% ZrO 2 , wherein Zr was stable in the network and no precipitation of ZrO 2 nanocrystals was observed. Moreover, the separation of phosphate‐rich phases in the as‐quenched glasses increased with the addition of ZrO 2 . The findings of the study revealed a dual role of ZrO 2 . First, ZrO 2 acted as a glass network former rather than a nucleation agent, increasing glass viscosity and the nucleation barrier of Li 2 SiO 3 through its strong network connectivity. Second, as Zr preferentially combined with non‐bridging oxygen to form Si–O–Zr linkages, a sufficient amount of charge‐balancing Li + ions existed in the network, which promoted the separation of phosphate‐rich phases. It indicated that the incorporation of ZrO 2 contributes to the activation of the nucleation role of P 2 O 5 , thus contributing to the formation of nanocrystals and fine microstructure of GCs.