The lattice location of three rare-earth ions (Pr3+, Ho3+, Yb3+) in LiNbO3 is investigated using Rutherford backscattering spectrometry/channeling techniques. All of them are found to occupy the Li+ octahedron but shifted from the Li+ regular position by different amounts (−0.45 Å for Pr3+, −0.38 Å for Ho3+, and −0.3 Å for Yb3+) as previously reported for other rare-earth ions. The amount of displacement is directly related to the variation of the ionic radius of the rare-earth ion, oppositely to transition metal ions which are not shifted. A simple model based on electronic configuration is given to account for this behavior.

Dihydroxybenzaldehyde (DHB) isomers can be oxidatively electrodeposited onto glassy carbon electrodes previously activated in base solution. We have studied the mechanism of such electrodeposition as well as the electrochemical features of films derived from 2,3-DHB, 3,4-DHB, 2,5-DHB, and 2,4-DHB isomers as well as related analogs including 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, and 4-nitrocatechol. The electrodeposition process and the electrochemical behavior of the modified electrodes were strongly dependent on pH as anticipated for quinone/hydroquinone functionalities. Glassy carbon electrodes modified with films derived from 2,3-DHB and 3,4-DHB exhibit catalytic activity in the electrooxidation of NADH. The catalytic currents are proportional to the concentration of NADH over the range 0.01−1.2 and 0.01−0.9 mM for films derived from 3,4-DHB and 2,3-DHB, respectively. These modified electrodes can be used in the design of biosensors based on coupled dehydrogenase enzymatic activities.

Optical absorption and fluorescence spectra have been systematically investigated in -doped crystals. The energy position and symmetry character of the Stark levels in the near-infrared region are deduced. The room-temperature absorption line strengths have been experimentally determined and the theory of Judd and Ofelt is used to obtain the radiative lifetimes and branching ratios of the emitting and states. Non-radiative relaxation processes are found to contribute to the transition probabilities of both states. In the case of the multiplets, a multiphonon relaxation process with an effective phonon energy of accounts for the temperature dependence of the lifetime. The -state luminescence shows a non-exponential decay time which indicates the existence of an energy transfer process. This energy transfer process exhibits a Boltzmann-type temperature dependence and is attributed to two-phonon-assisted energy transfer.