Titanium dioxide investigated with time-differential perturbed angular correlation at CERN

Titanium dioxide is commonly used in our everyday lives, from cosmetics to food coloring. A better characterization of the material could help improve its current use and may even open new doors for future applications. A new study has taken a fresh approach to studying the hyperfine structure of titanium dioxide by using time-differential perturbed angular correlation (TDPAC). Studying the hyperfine interactions is useful for the local characterization of a material and the method allowed the researchers to measure temperature dependence of hyperfine parameters and better understand lattice defects and irregularities in the material.

Schell et al. studied the hyperfine interactions in titanium dioxide with a cadmium probe using the Isotope mass Separator On-Line facility (ISOLDE) at CERN. A 1.4 gigaelectronvolt proton beam directed at the ISOLDE target produces a stream of ionized isotopes. The resulting radioactive beam is then directed at a sample surrounded by TDPAC sensors, which measure gamma rays emitted by the sample. Measurements were made both in a vacuum and in an annealing oxygen dioxide atmosphere.

“It’s an indescribable feeling to see the spectra in the computer screen knowing that it’s the result of the effort of more than hundreds of CERN workers,” said author Juliana Schell. “Moreover, ISOLDE-CERN is the only place in the world where one can implant ^111mCd and measure TDPAC spectra. The results are unique, reviewing two different local environments.”

The paper reports on previous TDPAC measurements of titanium dioxide in anatase and rutile phases, as well as the new experimental results collected at ISOLDE-CERN with cadmium as probe nuclei, and showed that the hyperfine parameters were highly sensitive to local changes in the non-stoichiometry of the rutile crystal structure.

Source: “A hyperfine look at titanium dioxide,” by J. Schell, D. Zyabkin, Doru C. Lupascu, Hans-Christian Hofsäss, M. O. Karabasov, A. Welker, and P. Schaaf, AIP Advances (2019). The article can be accessed at https://doi.org/10.1063/1.5097459 .