Hyperfine interactions and diffusion of Cd in TiO2 (rutile)

Abstract

In the current work, we present an investigation of the electronic and defect structure in (TiO2) rutile monocrystals by virtue of time differential perturbed angular γ-γ correlation spectroscopy. Studies were performed using 111mCd, implanted at ISOLDE/CERN complemented with diffusion studies and density functional theory calculations. Hyperfine field parameters have been probed as a function of temperature between 298 K and 873 K. The results demonstrate that 111mCd/Cd implanted rutile has two local environments. The first environment is characterized with parameters attributed to Cd localized at the cationic site which goes relatively along with a specific case where a charged supercell Cd:Ti(2e−) is in the scope. The origin of the second fraction could be rising from the subsurface regions where according to a tracer diffusion study the major part of implant is bounded featuring different diffusion mechanisms. Performed ab initio calculations suggest that the disruptive surface environment could contain apical or equatorial vacancies near the probe, inducing high electric field gradients for the second fraction. Current results seem to differ from those obtained before with different methods of probing (Ag/Cd and In/Cd).

Perturbed Angular Correlation Technique at ISOLDE/CERN Applied for Studies of Hydrogenated Titanium Dioxide (TiO2): Observation of Cd-H Pairs

“…Firstly, one points to the small damping of the R(t) function that reveals a low density of defects, with an essentially defect free local environment. Secondly, the main frequency measured at this temperature ω 01 = 96.52(3) Mrad•s −1 matches closely with previously reported values on rutile with Cd isotope [24,26]…”

“…The non-zero axially asymmetry parameter resembles results already measured at room temperature, although being slightly higher (η = 0.19(2) than previously measured values on single crystals (η = 0.07(1) [24,25]. Based on these results, one may presume that most of the atoms reside at the Ti substitutional site, in an essentially defects-free environment.…”

“…The corresponding R(t) function has a well-defined pattern, what is the characteristic of a single EFG/environment for the Cd atoms in TiO 2 , being only slightly damped as a function of time. The electric field gradient (EFG 1) resembles the values previously obtained on rutile [24,25]. Absence of significant remaining implantation damage is evidenced by several factors.…”

TDPAC Studies of Local Defects and Phenomena in Ferroics and Multiferroics

“…In addition, attractive defect-defect interactions may lead to the clustering of defects, even in diluted samples. TDPAC studies can play a key role in elucidating these effects in detail [52] (including defects caused by implantation [53,54]), especially if they are performed in association with self-diffusion studies [55,56].…”

Alternative Approaches to Study Mining and Mineral Science at ISOLDE-CERN

“…The self-diffusion method [24] has yet to be used for investigating diamond. Recently, the technique was used to study the incorporation of Cd into a titanium dioxide lattice [25]. For instance, this radiotracer technique was used to investigate the diffusion of all constituent elements in equi-atomic CoCrFeNi and CoCrFeMnNi [24].…”