It was recalled that the Zr(α) centre was the most prominent centre which was observed following the low-temperature X-irradiation of zircon. The centre was identified as being due to an electron trap in the form of a Zr3+ ion in the zircon lattice; with the centre being stabilized by interaction with a 100%-abundant I = 1/2 ion. Previous studies had explained the Zr(α) centre in terms of an 89Y3+ (I = 1/2) ion on a neighbouring Zr4+ site. By using both electron paramagnetic resonance and ENDOR techniques, it was clearly shown here that the I = 1/2 nuclear interaction was due to the presence of a 31P ion. A detailed analysis of the g and hyperfine matrices for 91Zr, 31P and 29Si was used to develop a model for the centre as an electron which was trapped on Zr as a Zr3+ ion with a P5+ ion on the nearest Si4+ site on the mirror plane. The defect was best described as being a [ZrPO4]0 centre.

An EPR/ENDOR Investigation of a [ZrPO4]0 Centre in X-Irradiated Zircon: the Zr(α) Centre. R.F.C.Claridge, W.C.Tennant, C.J.Walsby, S.Schweizer, J.M.Spaeth: Journal of Physics - Condensed Matter, 2000, 12[7], 1421-30