Understanding the local structure of Eu3+- and Y3+-stabilized zirconia: insights from luminescence and X-ray absorption spectroscopic investigations

Abstract

This study combines bulk structural and spectroscopic investigations of Eu3+- or Y3+/Eu3+ co-doped tetragonal and cubic zirconia polymorphs to gain an in-depth understanding of the solid solution formation process. Our bulk structural characterizations show that the dopant is homogenously distributed in the ZrO2 host structure resulting in an increase of the bulk symmetry with increasing dopant substitution (from 8 to 26 mol%). The local site symmetry around the Eu3+ dopant, however, determined with luminescence spectroscopy (TRLFS), remains low in all samples. Results obtained with X-ray pair distribution function and X-ray absorption spectroscopy show that the average coordination environment in the stabilized zirconia structures remains practically unchanged. Despite this very constant average dopant environment, site-selective TRLFS data show the presence of three nonequivalent Eu3+ environments in the ZrO2 solid structures. These Eu3+ environments are assumed to arise from Eu3+ incorporation at superficial sites, which increase in abundance as the size of the crystallites decrease, and incorporation on two bulk sites differing in the location of the oxygen vacancies with respect to the dopant cation.

Investigations towards incorporation of Eu3+ and Cm3+ during ZrO2 crystallization in aqueous solution

“…Both excitation peaks at 582.1 and 582.9 nm differ only minimally in their emission spectra, mainly in the relative intensities of the 7 F 1 and 7 F 2 bands. Thereby, the two Eu 3+ environments are very similar, and may differ only with respect to their coordination to the surrounding oxygen anions and created oxygen vacancies, as previously found for Eu 3+ incorporated in cubic ZrO 2 34 . More specifically, a coordination number of seven in the pristine monoclinic ZrO 2 environment would arise when the oxygen vacancy is not directly coordinated to the Eu 3+ cation, while a reduction of the coordination number to six would occur when a vacancy is directly coordinated to the incorporated Eu 3+ cation.…”

Immobilization of radiotoxic elements with Y‐stabilized zirconia: The thorium case

“…15 Interestingly, Ortho-I-II transition pressure is significantly reduced at higher temperatures, and this transformation takes place already at ∼12 GPa at T > 600 • C. 15,16 Various properties of ZrO 2 can be efficiently controlled by doping. 17 In particular, the introduction of Y 3+ ions is known to significantly influence a phase diagram of zirconia and to stabilize desired HT modifications. Specifically, tetragonal Y-stabilized zirconia (YSZ) phases, denoted as t′, can be obtained at ambient temperature for Y content of ca.…”

“…Various properties of ZrO 2 can be efficiently controlled by doping 17 . In particular, the introduction of Y 3+ ions is known to significantly influence a phase diagram of zirconia and to stabilize desired HT modifications.…”

Stability of doped zirconia under extreme conditions: Toward long‐term and secure storage of radioactive waste

“…Doping of zirconia, ZrO 2 , is widely used to stabilize a desired structural modification in diverse application fields. 4 For instance, introduction of yttrium allows one to obtain either tetragonal or cubic form of ZrO 2 , and the corresponding symmetry can be controlled by the amount of added Y. 5 The yttrium-stabilized zirconia phases (denoted as YSZ) are used, in particular, as host matrices for radiotoxic An elements since the YSZ family of compounds is known to incorporate substantial amount of these species.…”

“…Doping of zirconia, ZrO 2 , is widely used to stabilize a desired structural modification in diverse application fields 4 . For instance, introduction of yttrium allows one to obtain either tetragonal or cubic form of ZrO 2 , and the corresponding symmetry can be controlled by the amount of added Y 5 .…”