Samples were diluted with BN to give suitable absorption rates (concentrations calculated using MAX ) and pressed into pellets of 10 or 13 mm diameter. Spectra were recorded in transmission mode at ambient temperature using a Si (220) monochromator with ionization chamber detectors. For each pellet, several zones were sampled using 3 x 0.25 mm incident beam, and these were summed to produce the final spectra for analysis. Gd2O3, Tm2O3 and Yb2O3 were used as standards. The first coordination sphere Gd-O and Tm(Yb)-O distances were extracted by fitting each spectrum to a 1 x 1