Structural and mechanical modifications in Eu/Ho doped TiO2: Insights into phase transformation and strengthening mechanisms

Abstract

Titanium dioxide (TiO2) is renowned for its exceptional hardness, among metal oxides, rendering it indispensable in various applications. However, sol-gel-based TiO2 exhibits poor micromechanical properties compared with counterparts synthesized by other methods. This study aims to enhance the micromechanical properties through the co-doping of europium (Eu) and holmium (Ho) rare earth elements into the TiO2 crystal lattice. Accordingly, a notable increase in the microhardness of TiO2 (from 8.19 MPa to 36.34 MPa at 2 N) is achieved at a 5 % Eu-Ho doping rate. This improvement is attributed to the Hall-Petch strengthening mechanism resulting from the decrease in grain size (from 42 nm to 28 nm) and the corresponding changes in microstructure, including elemental composition, morphology, and crystal properties. The findings of the current study offer a new perspective on co-doped TiO2 as a promising candidate for nano and micro-scaled applications and also contribute to realistic long-term device design.