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When Eu(3+) ions occupy Ca(2+) sites of CaMoO(4), which has a body centered tetragonal structure with inversion symmetry, only the magnetic dipole transition ((5)D(0)→(7)F(1)) should be allowed according to Judd-Ofelt theory. Even if there are a few distortions in the Eu(3+) environment, its intensity should be more than that of the electric dipole transition ((5)D(0)→(7)F(2)). We report here the opposite effect experimentally and ascribe this to the polarizability effect of the MoO(4) tetrahedron, which is neighboring to EuO(8) (symmetric environment). The contribution of the energy transfer process from the Mo-O charge transfer band to Eu(3+) and the role of Eu(3+) over the surface of the particle could be distinguished when luminescence decay processes were measured at two different excitations (250 and 398 nm). Further, the luminescence intensities and lifetimes increase significantly with increasing heat-treatment temperature of the doped samples. This is attributed to the reduction of H(2)O from the surface of the particles and a non-radiative process after heat treatment.

In the present study, two distinct starting microstructures of Zr-2.5 wt% Nb have been used: (1) single-phase α hcp martensitic structure; and (2) two-phase, 10% bcc β and rest hcp α, Widmanstätten structure. In the second case, two types of α were present-near grain boundary predominantly single-phase α (about 5% of the total α) and α plates in an apparently continuous β matrix. Both (1) and (2) had similar starting crystallographic texture of the hcp α phase and were deformed by unidirectional and cross rolling. In the two-phase structure the changes in the bulk texture on cold rolling was found to be insignificant, while in the single-phase material noticeable textural changes were observed. Taylor type deformation texture models predicted textural changes in single-phase structure but failed to predict the observed lack of textural development in the two-phase material. Microtexture observations showed that α plates remained approximately single crystalline after cold rolling, while the β matrix underwent significant orientational changes. Relative hardening, estimated by X-ray peak broadening, was observed mainly in β phase; while aspect ratio of α plates remained unchanged with cold rolling-indicating absence of effective macroscopic strain in the hcp α plates. Based on microstructural and microtextural observations, a simple model is proposed in which the plastic flow is mainly confined to the β matrix within which the α plates are subjected to 'in-plane rigid body rotation'. The model explains the observed lack of textural developments in the two-phase structure.

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Nanoparticles of GdVO4 doped with Eu3+ and core/shell of GdVO4:Eu3+/GdVO4 are prepared by urea hydrolysis method using ethylene glycol as capping agent as well as reaction medium at 130 °C. Unit cell volume increases when GdVO4 is doped with Eu3+ indicating the substitution of Gd3+ lattice sites by Eu3+. From luminescence study, it is confirmed that there is no particle size effect on emission positions of Eu3+. Optimum luminescence intensity is found to be in 5–10 at. % Eu3+. Above these concentrations, luminescence intensity decreases due to concentration quenching effect. There is an enhancement in luminescence intensity of core/shell nanoparticles. This has been attributed to the reduction in surface inhomogenities of Eu3+ surroundings by bonding to GdVO4 shell. The lifetime for D50 level increases with annealing and core/shell formation.

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