We carried out a comprehensive crystal structure characterization of ${\mathrm{Li}}_2{\mathrm{Ti}}_x{\mathrm{Ru}}_{1-x}{\mathrm{O}}_3$ to investigate the effect of Ti-doping on the structural phase transition arising from the melting of the dimer solid around 550 K. Experimental tools sensitive to the average structure (x-ray diffraction), as well as those sensitive to local structure (extended x-ray absorption fine structure, EXAFS; pair distribution function, PDF) are used. We observed nonmonotonic dependence of the structural transition temperature on the Ti-doping level. At low doping, the transition temperature slightly increases with doping, while at high doping, the temperature decreases significantly with doping. We note two important observations from our studies. First, Ti K-edge EXAFS data show persistent Ti-Ru dimerization even with substantial Ti doping. Second, we were able to use the PDF data to estimate the correlation length above the transition temperature, which would correspond to the size of the proposed local ‘dimer clusters’ formed by Ru-Ru and Ti-Ru neighbors. The correlation length is found to be around 10 Å, which remains robust regardless of doping. Our study therefore suggests that ${\mathrm{Ti}}^{4+}$ with its $d^0$ electronic configuration is a special type of dopant when replacing Ru.

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• Chemical bonding
• Crystal structure
• Doping effects
• Structural phase transition
• X-ray absorption fine structure spectroscopy
• X-ray diffraction
• X-ray pair-distribution function analysis