title: Correlation between luminescence and EPR spectroscopy as evidence of ytterbium pair formation in Li6Ln(BO3)3:Yb3+ (Ln=Gd, Y) borate single crystals.
abstract: Synthesized powders and grown single crystals of nominal compositions Li(6)Ln(BO(3))(3):Yb(3+) (Ln=Y, Gd) were investigated by means of powder and single-crystal X-ray diffraction (XRD), as well as optical near-IR spectroscopy in conjunction with electron paramagnetic resonance (EPR) spectroscopy. The appearance of two distinct zero-phonon lines suggests the existence of two kinds of Yb(3+) ions in the single crystals. The XRD results exclude the possibility of a phase transition occurring between room and low temperatures. EPR spectra of single crystals show the presence of both isolated ions and pairs of ytterbium ions substituted for Y(3+). A strong temperature dependence of the intensity of Yb-Yb pairs resonance lines coincides with temperature dependence of emission peak at 978 nm, confirming a common origin of the defect giving rise to these spectra. Calculated from EPR spectra, the distance between pairs of Yb(3+) is in good agreement with crystallographic ones: R=3.856 Å, R(cryst) =3.849 Å.
authors.affiliation: Optical Materials, CNRS, Université de Bordeaux, ICMCB, 87 avenue du Dr. A. Schweitzer, Pessac, F-33608, France. jubera@icmcb-bordeaux.cnrs.fr
authors.forename: Véronique
authors.initials: V
authors.lastname: Jubera
authors.forename: Marie
authors.initials: M
authors.lastname: Chavoutier
authors.forename: Alla
authors.initials: A
authors.lastname: Artemenko
authors.forename: Philippe
authors.initials: P
authors.lastname: Veber
authors.forename: Matias
authors.initials: M
authors.lastname: Velazquez
authors.forename: Alain
authors.initials: A
authors.lastname: Garcia