In Situ Mullite Formation in 80 wt% Alumina Ceramics via Kaolin/Ca3(PO4)2 Ratio Modulation: Densification, Microstructural Evolution, and Dielectric Breakdown Behavior
- 1Advanced Ceramics Innovation & Research Center, Hanshan Normal University, Chaozhou 521041, China
- 2School of Materials Science and Engineering, Hanshan Normal University, Chaozhou 521041, China
- 3School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China
Abstract
Mullite–alumina composite ceramics were fabricated via in situ reaction sintering by modulating the kaolin-to-calcium phosphate (K/C) mass ratio (3, 6, 9, and 12) within an 80 wt% alumina matrix. The effects of liquid-phase sintering aid content on densification, phase evolution, microstructural development, and dielectric breakdown reliability were systematically investigated. X-ray diffraction confirmed corundum and mullite as the predominant phases across all compositions, with the mullite yield exhibiting a non-monotonic dependence on the K/C ratio. The optimal K/C ratio of 9 yielded the highest mullite content (9.15 wt%), the greatest bulk density (3.58 g·cm−3), and an apparent porosity (4.3%), attributable to a balanced liquid-phase volume and viscosity that promoted dissolution–precipitation transport while suppressing gas entrapment. Quantitative microstructural analysis revealed an average alumina grain size of 5.17 μm and uniform distribution of acicular mullite grains within the corundum matrix. Weibull statistical analysis of the dielectric breakdown strength for the optimal composition (K/C = 9) gave a characteristic breakdown strength E0 of 14.31 kV/mm and a Weibull modulus m > 20, indicating exceptional data reliability. The high breakdown resistance is ascribed to the synergistic effects of reduced porosity, increased grain boundary density, and residual compressive stresses at mullite–corundum interfaces. These findings establish a quantitative correlation among liquid-phase content, microstructural optimization, and dielectric reliability, providing a framework for the compositional design of cost-effective alumina-based energy storage ceramics.
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BibTeX
@article{lin2026situ,
title = {{In Situ Mullite Formation in 80 wt% Alumina Ceramics via Kaolin/Ca3(PO4)2 Ratio Modulation: Densification, Microstructural Evolution, and Dielectric Breakdown Behavior}},
author = {Shaomin Lin and Yaling Yu and Xin Chen and Haiyin Huang and Leilei Cai and Wei Xu and Chenyang Zhang},
journal = {Inorganics},
year = {2026},
month = oct,
doi = {10.3390/inorganics14100263},
url = {https://www.mdpi.com/2304-6740/14/10/263},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - In Situ Mullite Formation in 80 wt% Alumina Ceramics via Kaolin/Ca3(PO4)2 Ratio Modulation: Densification, Microstructural Evolution, and Dielectric Breakdown Behavior
AU - Shaomin Lin
AU - Yaling Yu
AU - Xin Chen
AU - Haiyin Huang
AU - Leilei Cai
AU - Wei Xu
AU - Chenyang Zhang
PY - 2026
DA - 2026/10/15
JO - Inorganics
DO - 10.3390/inorganics14100263
UR - https://www.mdpi.com/2304-6740/14/10/263
AB - Mullite–alumina composite ceramics were fabricated via in situ reaction sintering by modulating the kaolin-to-calcium phosphate (K/C) mass ratio (3, 6, 9, and 12) within an 80 wt% alumina matrix. The effects of liquid-phase sintering aid content on densification, phase evolution, microstructural development, and dielectric breakdown reliability were systematically investigated. X-ray diffraction confirmed corundum and mullite as the predominant phases across all compositions, with the mullite yield exhibiting a non-monotonic dependence on the K/C ratio. The optimal K/C ratio of 9 yielded the highest mullite content (9.15 wt%), the greatest bulk density (3.58 g·cm−3), and an apparent porosity (4.3%), attributable to a balanced liquid-phase volume and viscosity that promoted dissolution–precipitation transport while suppressing gas entrapment. Quantitative microstructural analysis revealed an average alumina grain size of 5.17 μm and uniform distribution of acicular mullite grains within the corundum matrix. Weibull statistical analysis of the dielectric breakdown strength for the optimal composition (K/C = 9) gave a characteristic breakdown strength E0 of 14.31 kV/mm and a Weibull modulus m > 20, indicating exceptional data reliability. The high breakdown resistance is ascribed to the synergistic effects of reduced porosity, increased grain boundary density, and residual compressive stresses at mullite–corundum interfaces. These findings establish a quantitative correlation among liquid-phase content, microstructural optimization, and dielectric reliability, providing a framework for the compositional design of cost-effective alumina-based energy storage ceramics.
SN - 2304-6740
ER -