Solid-State NMR Characterization of Synroc
EMSL Project ID
2311
Abstract
Synroc is a titanate based multiphase ceramic developed for immobilizing high level waste from nuclear fuel reprocessing. The main constituent phases are zirconolite (CaZrTi2O7), perovskite (CaTiO3), hollandite (Ba(Al,Ti)2Ti6O16) and reduced rutile (TiO2). It can also contain nearly all fission products and actinides from high level waste in dilute solid solution. There has already been a large synthetic effort directed at producing the individual components, such that isotopic labels have been incorporated to facilitate NMR analysis. Previous efforts at natural abundance 47/49Ti solid state NMR generate complicated powder pattern as the gyromagnetic ratios of each isotope are very close. In the case of 91Zr the width of the line (due mainly to large quadrupole coupling interactions) has typically prohibited the use of solid state NMR and forced the researchers to turn to NQR methods. However with the advent of high field instrumentation such as the 18.8 T medium bore magnet, there is now the possibility of looking at these metals and extracting information about their environments. During previous proposal periods there has been significant work performed by EMSL staff (Jesse Sears) to design and construct a static probe to yield undistorted 47/49Ti lineshapes. Initial measurements were plagued with piezoelectric and acoustic ringing artifacts, as depicted in Figs. 1(a) and 1(b). As a result of a major probe redesign (i.e. moving the tuning capacitors out of the field and changing the probe wire geometry) we have been able to acquire acceptable lineshapes from basic titanates such as anatase (see Fig. 1(b)), rutile (see Fig. 2), BaTiO3, CaTiO3, MgTiO3, CdTiO3 (perovskite and ilmenite) fresnoite, etc. We have also been able to acquire some single crystal data on systems where single crystal growth has been possible (see Fig. 3). Furthermore, some very impressive 91Zr static lineshapes have also been acquired form some basic zirconia systems such as monoclinic ZrO2, tetragonal ZrO2 and zircon. This represents a major step forward as they have all been measured as a single broad NMR lineshape, whereas previous studies of these systems at lower fields have needed to resort to time consuming point-by-point acquisitions or the NQR technique.
Project Details
Project type
Capability Research
Start Date
2001-10-01
End Date
2002-04-01
Status
Closed
Released Data Link
Team
Principal Investigator