Next translucent glass-ceramics: Amorphous alumina boosts strength and toughness

2025-02-13

(Press-News.org)

Zirconia-based ceramics, particularly 3Y-TZP, have transformed dental restorations, enabling the development of durable all-ceramic crowns and fixed prostheses. However, their inherent opacity necessitates the application of a porcelain layer, which is prone to chipping and debonding. To address this, translucent glass ceramics (GCs) have been developed and commercialized, including mica-based, leucite-based, and lithium disilicate GCs. These materials offer excellent aesthetics and bondability due to their controlled crystallization process, but their brittleness and low fracture resistance restrict their applications to inlays, onlays, and small anterior restorations. Recently, a ZrO2-SiO2 nanocrystalline glass ceramic has been developed, where the ZrO2 nanocrystals are embedded into the amorphous SiO2 matrix. To further enhance the properties of these glass ceramics, yttrium oxide has been introduced as a dopant. The yttrium ions were found to segregate at the grain boundary (GB) of ZrO2 crystalline, and this segregation increases the work of separation. The indentation toughness reaches 6.69 MPa∙m1/2. Al2O3, widely used in prosthetic bearings due to its high mechanical strength and good wear performance, has also shown potential for improving the mechanical properties of glass ceramics. The segregation of Al3+ at grain boundaries is expected due to its size and charge mismatch with Zr4+, as well as its low solubility in TZP.

Recently, a team of ceramic scientists led by Wei Xia from Uppsala University, Sweden reported Al2O3-ZrO2-SiO2 nanocrystalline GCs synthesized via spark plasma sintering, systematically analyzing their microstructure, optical properties, and mechanical behavior to assess their potential for advanced dental applications. This work significantly improved mechanical performance.

The team published their work in Journal of Advanced Ceramics on January 09, 2025.

In this study, they developed highly translucent and toughened ZrO2-SiO2 glass matrix nanoceramics enhanced by amorphous Al2O3. The segregation and content of Al³⁺ at the grain boundaries of ZrO₂ nanocrystals play a crucial role in modulating the microstructure and mechanical properties of the resulting glass ceramics. ZrO₂ nanocrystals are embedded within the amorphous SiO₂ matrix, with Al³⁺ ions preferentially segregating at the grain boundaries. Additionally, localized Al³⁺-rich domains were observed, attributed to the low solubility of Al₂O₃ in the system.

An increase in Al₂O₃ and SiO₂ content effectively reduces the monoclinic phase fraction and limits grain growth, leading to improved stabilization of the tetragonal phase. The 10 mol% Al₂O₃ composition exhibited the smallest grain size (38 nm), achieving the highest translucency and fracture toughness of 8.05 MPa·m¹/², demonstrating strong potential for dental applications. Meanwhile, the 5Al-65Zr-30Si composition exhibited a higher flexural strength of 960 MPa. The enhanced mechanical properties are attributed to the synergistic effects of the ZrO₂ 3D nanostructure and Al³⁺ segregation at grain boundaries, which modifies bonding energy and improves mechanical performance.

This work was supported by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 812765, Swedish Research Council (2020-04341) and Carl Tryggers Foundation (CTS 21:1704). We also thank Myfab Uppsala for providing facilities and experimental support. Myfab is a national research infrastructure funded by the Swedish Research Council (2019-00207).

About Author

Dr. Wei Xia is a professor of Applied Materials Science at Department of Materials Science and Engineering at Uppsala University, Sweden. His research group consists of researchers from diverse backgrounds, including chemistry, materials science, physics, and biotechnology. His research focuses on the synthesis of bio- and customized materials, with key areas including: Advanced glass-ceramics/ceramics for dental and spinal applications; Nano-structured bioactive ceramics for bone repair and regeneration; Antipathogenic materials; Interactive implants. The group maintains strong collaborations with hospitals and industries worldwide. Prof. Xia has published over 200 scientific papers and conference proceedings, authored five book chapters, and edited a book on biomaterials. He holds more than 40 patents across different patent families. Currently, he serves as the president of the Academy of Ceramic Odontology in Sweden and is an editorial board member of Bioactive Materials and other academic journals.

Zhou Huasi, Ph.D. from Uppsala University, focuses on high-performance silica-based glass-ceramics. She has published multiple articles in journals such as Journal of Advanced Ceramics (JAC), Journal of the European Ceramic Society (JECS), Ceramics International, Applied Surface Science, International Journal of Applied Ceramic Technology, Biomedical Materials Devices, and Journal of Materials Chemistry B.

About Journal of Advanced Ceramics

Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen. JAC’s 2023 IF is 18.6, ranking in Top 1 (1/31, Q1) among all journals in “Materials Science, Ceramics” category, and its 2023 CiteScore is 21.0 (top 5%) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508

About SciOpen

SciOpen is an open access resource of scientific and technical content published by Tsinghua University Press and its publishing partners. SciOpen provides end-to-end services across manuscript submission, peer review, content hosting, analytics, identity management, and expert advice to ensure each journal’s development. By digitalizing the publishing process, SciOpen widens the reach, deepens the impact, and accelerates the exchange of ideas.

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Next translucent glass-ceramics: Amorphous alumina boosts strength and toughness

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