To examine the relations between local structures around O and O K-edge spectral features, we extract ∆E and the ratio of intensities of peak A to peak B, I A /I B , from each spectrum and plot as a function of the coordination number (CN ) of oxygen atoms (Fig. ). The coordination numbers are measured using the effective coordination number definition proposed by Hoppe . As also shown in Fig. (C2/m), which are stable up to high temperatures of around 1400 • C under ambient pressure.