ZHANG Caicai ^{1 ,2}, CHEN Ruwei ¹, CHEN Zhenhui ¹, LIN Man ¹, XUE Yongjie ^{1, 2}, DENG Tengfei ^{1, 2}

(1. Chaozhou Branch Center, Guangdong Laboratory of Chemistry and Fine Chemicals (Hanjiang Laboratory),

Chaozhou 521000, Guangdong, China; 2. State Key Laboratory of Silicate Materials for Architectures,

Wuhan University of Technology, Wuhan 430070, Hubei, China)

Extended abstract:

[Background and purposes] Jade-like porcelains are prone to pyroplastic deformation during high-temperature sintering, which compromises product dimensional accuracy and yield. While the effects of chemical composition are well-studied, the role of particle size of the raw materials, particularly silica (SiO₂), remains insufficiently understood. This study was aimed to systematically study the effect of SiO₂ particle size on the pyroplastic deformation behavior, aiming to elucidate the underlying mechanisms related to liquid phase formation and viscosity.

[Methods] Green bodies with a clay-feldspar-quartz formulation (10 wt.% SiO₂) were prepared using five SiO₂ powders with median particle sizes (D₅₀) ranging from 47 to 152 μm. Samples were fabricated via wet ball milling, dry pressing (10 MPa) and sintering at 1180–1260 ℃. Phase composition and microstructure were characterized by using XRD and SEM-EDS. Pyroplastic deformation index (PI) was measured by using a standardized method. Liquid phase viscosity was calculated using the modified M-SW model based on the EDS-derived chemical compositions.

[Results] Reducing SiO₂ particle size promoted densification, allowing vitrification at 1220 ℃ for finer particles, whereas coarser SiO₂ particles required 1240 ℃. The PI increased with increasing temperature and decreasing particle size. At 1260 ℃, the sample with the finest SiO₂ (D₅₀=47 μm) exhibited the maximum PI of 1.87×10⁴ mm⁻¹. Quantitative analysis of quenched samples revealed that decreasing the SiO₂ particle size from 152 μm to 47 μm increased the liquid phase content from 81.58% to 90.74% and decreased the calculated viscosity from 14273.44 Pa·s to 11839.91 Pa·s. The enhanced deformation is attributed to the combined effect of the increased liquid phase volume and reduced viscosity, which facilitated particle rearrangement and viscous flow.

[Conclusions] The mechanism of SiO₂ particle size to influence the high-temperature plastic deformation of jade-like porcelain was clarified. Finer SiO₂ particles accelerated densification, significantly increased liquid phase content and slightly reduced liquid phase viscosity at high temperatures. These changes synergistically enhance viscous flow, leading to increase in macroscopic deformation. It has been demonstrated that regulating SiO₂ particle size is an effective strategy for coordinating liquid phase properties, thus providing a theoretical basis for optimizing sintering processes and controlling dimensional stability of high-quality porcelain production.

Key words: SiO₂ particle size; pyroplastic deformation; liquid phase content; M-SW model