Perturbed angular correlation measurement of the electric field gradient at 181Ta in ZrSiO4 and HfSiO4

Abstract

We have used time-differential perturbed angular correlation (PAC) spectroscopy with 181 Ta-probes to study the electric field gradient at Zr-sites in synthetic zircon and hafnon between room temperature and 1,200 • C. PAC spectra are similar to those obtained from naturally occurring zircons. In particular, a change in slope of the quadrupole coupling vs. temperature is observed in the synthetic zircon at the same temperature as seen in natural zircons from the Mud Tank carbonatite (Australia). The synthetic hafnon data also shows this feature but at somewhat higher temperature. Low-temperature PAC spectra of both synthetic zircon and hafnon have a clearly reduced anisotropy. We believe that the cause for this is a electronic defect, possibly created during the β-decay of the probe parent nucleus.

Phase quantification of mullite–zirconia and zircon commercial powders using PAC and XRD techniques

“…2a) had to be assumed to achieve a satisfactory fit: the interaction describing crystalline zircon [5,6], hereinafter named cz, and an unknown and highly asymmetric interaction, xz in the following. The abundance ratio found for these sites was 1:1.…”

“…The hyperfine quadrupole interaction at Zirconium sites of monoclinic zirconia [4] and zircon [5,6] crystalline lattices are perfectly known.…”

Soft Hydrothermal Synthesis of Hafnon, HfSiO4

“…From a general point of view, the synthesis of HfSiO 4 was reported by high temperature solid state chemistry, 1,5,7,13,[21][22][23][24][25] sol-gel methods, 12,26,27 chemical transport reaction, 14,28,29 physical vapor deposition 30 and hydrothermal synthesis. 31,32 However, the only hydrothermal syntheses were reported by Caruba et al under acid conditions at T = 800°C, 75 MPa, 31 and by McNeil et al in very acid conditions, i.e.…”

PAC study in the HfO2–SiO2 system

“…5b. The spectrum for the annealed sample was fitted assuming the existence of a predominant interaction characterized by the following hyperfine parameters: According to the literature this main component can be associated with the formation of HfSiO 4 (hafnon) [3,8]. The rest of the probes are in defective phases with unknown stoichiometry.…”