Luminescence of Gd₂(WO₄)₃:Ln³⁺at ambient and high hydrostatic pressure

Abstract

This paper presents a spectroscopic characterization of Gd(2)(WO(4))(3):Ln(3+) (Ln=Eu, Pr, Tb and Dy). The luminescence and luminescence kinetics were measured under pressures up to 250 kbar. It was found that pressure quenches the luminescence of Pr(3+) and Tb(3+), whereas the emission of Eu(3+) and Dy(3+) was stable up to 250 kbar. This effect was related to a decrease in the ionization energy of Pr(3+) and Tb(3+) caused by pressure induced increase in energies of the Ln(2+) and Ln(3+) ions with respect to the band edges. Analysis of emission and excitation spectra allowed us to estimate the energies of the ground states of Ln(3+) and Ln(2+) with respect to the valence and conduction band edges of the Gd(2)(WO(4))(3) host. Differences between energies of the ground states of Ln(2+) and Ln(3+) have also been calculated.

High‐pressure phase transitions and properties of MTO4 compounds with the monazite‐type structure

“…A third subject of interest in the future is the study under HP of the emission bands of the rare‐earth ions. Such studies have been carried out under compression in scheelite‐type MTO 4 oxides and in systems with more complex crystal structures . They can be useful for the accurate detection of phase transition and to explore how the local environment around the rare‐earth metal is distorted under compression and how it is modified after the pressure‐induced phase transitions.…”

Energy levels in CaWO4:Tb3+at high pressure

“…[11][12][13][14][15] In the case of Pr 3+ or Tb 3+ doped samples, the emission dynamics are influenced by the formation of an intermediate charge transfer state (or the impurity trapped exciton state) that interferes with the 4f excited states of the dopants by creating new relaxation channels that lead to the quenching of otherwise emitting levels. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] The ionization transition creates the Ln 4+ ion (Ln = Tb, Pr) and an electron in the conduction band (e cb ). After ionization, the Coulomb attraction between Ln 4+ and e cb allows the system to exist in the bound state, which defines an impurity trapped exciton (ITE) state (also referred to the praseodymium/terbium trapped exciton (PTE/TTE) state) in the past literature.…”

“…After ionization, the Coulomb attraction between Ln 4+ and e cb allows the system to exist in the bound state, which defines an impurity trapped exciton (ITE) state (also referred to the praseodymium/terbium trapped exciton (PTE/TTE) state) in the past literature. [17][18][19][20][21][22][23][24][25][26][27] In the equivalent description of this process the excitation bands corresponding to Pr 3+ (or Tb 3+ )-W 6+ intervalence charge transfer (IVCT) are considered as a transition where the electron is transferred from Pr 3+ to nearby W 6+ cations. 15,[29][30][31][32][33][34][35] It should be noted that the different labels IVCT and ITE (or PTE/TTE) refer to the same phenomenon.…”

Luminescence Spectra of β-SiAlON/Pr3+ Under High Hydrostatic Pressure

“…The red shift of the emission lines for the Pr 3+ ions in 2b and 2a sites are similar. The respective rates range from −0.5 to −0.9 cm –1 /kbar and are small in comparison to the values of −1.75–4.1 cm –1 /kbar observed for Pr 3+ in oxide matrixes. − Furthermore, in oxides doped with Pr 3+ , the intensity of the luminescence from the 3 P 0 state was strongly quenched with increasing pressure. This effect has been attributed to the decrease of energy of the ITE state with respect to energies of the states of the 4f 2 electronic configuration of Pr 3+ .…”