Spectroscopic Studies of SrTiO3Using Impurity-Ion Probes

Abstract

Sharp-line fluorescence and absorption in the region of 7935 A were observed in Cr 3+ -doped and undoped SrTiC>3. It is reasonably established that the fluorescence and absorption are due to the 2 E <-> *A 2 transition (R line) of the Cr 3+ ion. Polarization and absorption measurements indicate that the i?-line transition is magnetic dipole. Fluorescence from Mn 4+ -doped SrTi03 was seen at about 7230 A. At low temperatures, a temperature-dependent splitting of the i?-line transition of Cr 3+ is seen. It is shown that this is due to the lifting of the degeneracy of the 2 E state by the temperature-dependent tetragonal field present in SrTiOs below 103±2°K. These results are compared with previous measurements on rare-earth ions in SrTi0 3 . The possible origin of the tetragonal transition is discussed.

Fluorescence of doped nanocrystalline insulating materials: Effects of structural phase transitions

“…The observed spectra were similar to that of the bulk doped SrTiO 3 [3] (Fig. 1 line-broadening observed in nanocrystalline samples caused by the larger random electric fields and strains in nanocrystals which may be due to the increased role of the surface.…”

“…1 line-broadening observed in nanocrystalline samples caused by the larger random electric fields and strains in nanocrystals which may be due to the increased role of the surface. The peculiar highly asymmetric shape of inhomogeneously broadened zero-phonon Cr 3+ R-line may be explained by the large nonlinear R-line shift in the electric field [3]. The large inhomogeneous broadening makes the observation of the R-line splitting in the D 4h phase [3] impossible, at least without the use of the fluorescence line narrowing (FLN) technique.…”

“…The peculiar highly asymmetric shape of inhomogeneously broadened zero-phonon Cr 3+ R-line may be explained by the large nonlinear R-line shift in the electric field [3]. The large inhomogeneous broadening makes the observation of the R-line splitting in the D 4h phase [3] impossible, at least without the use of the fluorescence line narrowing (FLN) technique. In order to detect the phase transition in SrTiO 3 :Cr 3+ nanocrystals the shift of the Rline with temperature was studied (see Fig.…”

Luminescence and optical absorption in nominally pure and Cr‐doped PLZT ceramics

“…They are shifted to the red spectral region, e.g., in comparison with ruby (693.8 to 691.3 nm). This effect is typical of chromium-doped ABO, compounds, e.g., the R line of SrTiO, at 77 K is peaked at 793.5 nm [29] and 745.0 nm in KTaO, [7, 301. A decrease of the ,E + 4A, transition energy is connected with the low value of the B parameter, which is a measure of the d-valence electron-electron interaction reduced by the covalency of ABO, materials. In PLZT B = 560 cm-' as compared with B = 850cm-' in ruby.…”

Nanocrystalline SrTiO3:Eu3+ and BaTiO3:Eu3+: fluorescence spectroscopy and optical studies of structural phase transitions

“…The sharp-line optical spectra of impurity ions are sensitive to these ions environment and thus may serve as efficient probes of structural phase transitions [3][4][5]. In present study Eu 3+ fluorescence was used to study structural phase transitions in nanocrystalline SrTiO 3 .…”