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Ceria-stabilized tetragonal zirconia polycrystal (Ce-TZP) has exceptional fracture toughness and flaw tolerance due to facile t‒m phase transformation toughening. However, its wider-range applications are limited by its relatively low strength due to its large grain size and low transformation stress, which results in yield-like failure. Here, we combined additive manufacturing (AM), pressureless two-step sintering, and hot isostatic pressing (HIP), and addressed the challenging grain size refinement problem in Ce-TZPs. We successfully produced dense ultrafine-grained Ce-TZP ceramics with an average grain size below 500 nm, a three-point bending strength above 800 MPa, and a single-edge-notch-beam fracture toughness in the range of 11‒12 MPa·m1/2. The critical roles of processing design, mixed Ce valences, and under- vs. over-stabilization of tetragonal polymorphs were noted. Our work offers insights and strategies for the future development of stronger and tougher Ce-TZP ceramics that can compete with tetragonal yttria-stabilized zirconia in various applications, including additive manufacturing.


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Grain size refinement of additive manufactured Ce-TZP ceramics by coupled two-step pre-sintering and HIP

Show Author's information Ruoshi ZhaoHongbing YangXintong LiuHezhen LiChang-An WangJing Ma( )Yanhao Dong( )
State Key Lab of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China

Abstract

Ceria-stabilized tetragonal zirconia polycrystal (Ce-TZP) has exceptional fracture toughness and flaw tolerance due to facile t‒m phase transformation toughening. However, its wider-range applications are limited by its relatively low strength due to its large grain size and low transformation stress, which results in yield-like failure. Here, we combined additive manufacturing (AM), pressureless two-step sintering, and hot isostatic pressing (HIP), and addressed the challenging grain size refinement problem in Ce-TZPs. We successfully produced dense ultrafine-grained Ce-TZP ceramics with an average grain size below 500 nm, a three-point bending strength above 800 MPa, and a single-edge-notch-beam fracture toughness in the range of 11‒12 MPa·m1/2. The critical roles of processing design, mixed Ce valences, and under- vs. over-stabilization of tetragonal polymorphs were noted. Our work offers insights and strategies for the future development of stronger and tougher Ce-TZP ceramics that can compete with tetragonal yttria-stabilized zirconia in various applications, including additive manufacturing.

Keywords: zirconia, two-step sintering, additive manufacturing (AM), hot isostatic pressing (HIP), grain size refinement

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Publication history

Received: 09 January 2024
Revised: 20 March 2024
Accepted: 21 March 2024
Published: 21 May 2024
Issue date: May 2024

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© The Author(s) 2024.

Acknowledgements

Acknowledgements

This work is supported by the National Key R&D Program of China (No. 2023YFB3812000), the National Natural Science Foundation of China (No. 51972189), and the Tsinghua University Initiative Scientific Research Program (No. 20233080030). The authors are grateful for Prof. James Zhijian Shen’s guidance, especially on the mentorship of the lead author Ruoshi Zhao. The work cannot be done without the insights and help from Prof. James Zhijian Shen. The authors would also like to thank Prof. Zhipeng Xie for insightful discussion.

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This is an open access article under the terms of the Creative Commons Attribution 4.0 International License (CC BY 4.0, http://creativecommons.org/licenses/by/4.0/).

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