The structural data obtained from of high resolution optical spectroscopic investigations on Nd3+, Eu3+ and Yb3+ ions in rare earth calcium oxoborate crystals RCOB, mainly GdCOB and YCOB, but also EuCOB, are compared with those obtained from other studies such as X-ray diffraction or differential thermal analysis. The dependence of non-equivalent center intensities and on R3+ (dopants) ionic radii is in qualitative accord with X-ray diffraction data. The glassy like behavior of 4F3/2 Nd3+ emission under selective excitation, as well as the shift of one line of 5Do → 7F1 Eu3+ emission are explained in terms of cationic structural disorder of RCOB crystals.
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