Luminescence and properties of La2O3-B2O3-M2O5:Ln(M=Nb(V) or Ta(V)) and La2O3-B2O3-M2O5-PbO/Bi2O3 glasses

New glasses of (19-y)La2O3-(81-x)B2O3-xM 2O5: yLn3+ (M= Nb or Ta; Ln= lanthanide ion) and 19La2O3-(61-z)B2O3-20Nb2 O5-zPbO/Bi2O3 composition have been prepared and characterized. Homogeneous transparent glasses are obtained with concentrations up to 20 mol% Nb2O5, 10 mol% Ta2O5, PbO or Bi2O3 and 3 mol% Ln3+. These glasses have large chemical resistance and surface hardness, high refractive indices, excellent transparency in the visible IR region (400-1800 nm), and intense UV absorption. The luminescence of niobate and tantalate MO6 groups is reported for the first time in glasses. Intense luminescence is observed for Eu3+, Dy3+, Tb3+, or Tm3+ in 19La2O3-61B2O3-20Nb2O5 glasses upon UV excitation into the MO6 groups, showing that these materials are interesting hosts for optically active Ln ions. (orig.)