# Optimal CeO2 Doping for Synergistically Enhanced Mechanical, Tribological, and Thermal Properties in Zirconia Ceramics

## TL;DR

Adding 15% cerium oxide to zirconia ceramics improves hardness, reduces friction, and lowers thermal expansion, but adding more than 15% causes performance to decline.

## Contribution

The study systematically correlates mechanical, tribological, and thermal properties of CeO2-doped ZrO2 ceramics, revealing their interdependent trade-offs.

## Key findings

- 15 wt.% CeO2 achieves peak hardness (310 HV1), lowest friction (0.205), and 72.2% lower thermal expansion.
- Excess CeO2 (>15 wt.%) causes agglomeration, grain coarsening, and increased porosity, degrading performance.
- Optimal doping enables simultaneous tuning of mechanical strength, wear resistance, and thermal management.

## Abstract

What are the main findings?
Optimal performance at 15 wt.% CeO2: peak hardness, lowest friction (0.205), and 72.2% lower thermal expansion.Enhancements from solid solution strengthening, grain refinement, and phonon scattering via point defects.Excess doping (>15 wt.%) leads to CeO2 agglomeration, grain coarsening, and increased porosity.

Optimal performance at 15 wt.% CeO2: peak hardness, lowest friction (0.205), and 72.2% lower thermal expansion.

Enhancements from solid solution strengthening, grain refinement, and phonon scattering via point defects.

Excess doping (>15 wt.%) leads to CeO2 agglomeration, grain coarsening, and increased porosity.

What are the implications of the main findings?
Provides a clear compositional guideline (15 wt.% CeO2) for designing high-performance ZrO2 ceramics.Warns against over-doping, emphasizing precise compositional control for optimal microstructure.Enables simultaneous tuning of mechanical strength, wear resistance, and thermal management.

Provides a clear compositional guideline (15 wt.% CeO2) for designing high-performance ZrO2 ceramics.

Warns against over-doping, emphasizing precise compositional control for optimal microstructure.

Enables simultaneous tuning of mechanical strength, wear resistance, and thermal management.

CeO2 doping is a well-established strategy for enhancing the properties of zirconia (ZrO2) ceramics, with the prior literature indicating an optimal doping range of around 10–15 wt.% for specific attributes. Building upon this foundation, this study provides a systematic investigation into the concurrent evolution of mechanical, tribological, and thermophysical properties across a broad compositional spectrum (0–20 wt.% CeO2). The primary novelty lies in the holistic correlation of these often separately examined properties, revealing their interdependent trade-offs governed by microstructural development. The 15Ce-ZrO2 composition, consistent with the established optimal range, achieved a synergistic balance: hardness increased by 27.6% to 310 HV1, the friction coefficient was minimized to 0.205, and the wear rate was reduced to 1.81 × 10−3 mm3/(N m). Thermally, it exhibited a 72.2% reduction in the thermal expansion coefficient magnitude at 1200 °C and a low thermal conductivity of 0.612 W/(m·K). The enhancement mechanisms are consistent with solid solution strengthening, grain refinement, and likely enhanced phonon scattering, potentially from point defects such as oxygen vacancies commonly associated with aliovalent doping in oxide ceramics, while performance degradation beyond 15 wt.% is linked to CeO2 agglomeration and duplex microstructure formation. This work provides a relatively comprehensive insight into the dataset and mechanism, which is conducive to the fine design of multifunctional ZrO2 bulk ceramics. It is not limited to determining the optimal doping level, but also aims to clarify the comprehensive performance map, providing reference significance for the development of advanced ceramic materials with synergistically optimized hardness, wear resistance, and thermal properties.