Overall phase analysis of Eu-doped ZnO Overall phase analysis of Eu-doped ZnO with 0, 5, 10, 20, and 33 mol% EuO1.5 in ZnO (ZnO:0-33Eu) were made with powder-XRD and IR spectroscopy to investigate the metastable limit for carbonate-free Eu-oxide doping of ZnO without phase separation, i.e. with retained h-ZnO XRD patterns and Zn-O vibration peak in the IR spectra.