Luminescence and Location of Gd³⁺ or Tb³⁺ Ions in Perovskite-Type LaScO₃

Abstract

The luminescence properties of Gd or Tb ions at La and Sc sites were investigated in LaScO with a distorted perovskite-type structure (ABO). Although the luminescence of lanthanide ions located at B sites is not common and has not been examined in detail, Gd or Tb luminescence from B sites and A sites is clearly observed in Gd- or Tb-doped LaScO. The differences in the luminescence characteristics concern peak positions, peak shapes, and decay time, which are all influenced by the crystal field and the site symmetry. The UV luminescence of Gd at B sites shows a red shift compared to Gd at A sites, and the green luminescence of Tb at B sites contrasts with the blue-violet and green luminescence of Tb at A sites. The decay time of the luminescence from B sites is systematically longer than that from A sites in both the Gd and Tb cases.

Site Dependence of Tb3+ Luminescence in Double Perovskite-Type Alkaline Earth Lanthanum Tantalates

“…excitation peaks in the range from 220 to 250 nm. [5][6][7][25][26][27][28][29] The crystal site of Tb 3+ in this assignment is consistent with the results obtained by XRD and XANES measurements. In the PL spectra measured under UV excitation at 247 nm, the Tb 3+ luminescence is composed with two series of transitions from 5 D 3 to 7 F J (J = 6, 5, 4, 3) and from 5 D 4 to 7 F J states.…”

“…The XANES spectra in Figure revealed that the crystal field splitting for Tb 5d orbitals in BLTO is as large as 3 eV, which would be larger than the centroid shift. Accordingly, the red-shift of the 4f–5d excitation peak in BLTO:Tb 3+ is primarily attributed to the larger crystal field at the B sites than that at the A sites, which is also observed in some perovskite-type oxides such as LaScO 3 and LaLuO 3 . , The preference of B-site occupation by Tb 3+ in BLTO:Tb 3+ observed in the PLE examination is consistent with the results of the XRD and XANES analyses. It is also worth noticing in the PL spectra that only the Tb 3+ luminescence derived from the 5 D 4 – 7 F J transitions is observed for BLTO:Tb 3+ .…”

“…The PLE spectrum of CLTO:Tb 3+ , which monitored the PL peak at 550 nm, exhibits an intense peak at 247 nm, just below the absorption edge of the HL. This intense peak is assigned to the allowed 4f–5d transition and matches with Tb 3+ at A sites because Tb 3+ at A sites in several Tb 3+ doped perovskite-type oxides usually gives the 4f–5d excitation peaks in the range from 220 to 250 nm. − ,− The crystal site of Tb 3+ in this assignment is consistent with the results obtained by XRD and XANES measurements. In the PL spectra measured under UV excitation at 247 nm, the Tb 3+ luminescence is composed of two series of transitions from 5 D 3 to 7 F J (J = 6, 5, 4, 3) and from 5 D 4 to 7 F J states.…”

“…The absence of the luminescence from the 5 D 3 – 7 F J transitions for BLTO:Tb 3+ provides a marked contrast to the PL spectrum for CLTO:Tb 3+ . These features are also almost the same with those found in Tb 3+ doped LaScO 3 and LaLuO 3 implying that the 5d levels of Tb 3+ at B sites lie more downside in energy than those at A sites. , …”

“…Recently, site-sensitive luminescence properties of Tb 3+ were reported in some distorted simple perovskite-type oxides (ABO 3 ), namely LaScO 3 and LaLuO 3 . , Even though Tb 3+ at both A and B sites led to a similar green luminescence ( 5 D 4 – 7 F J transitions) under UV excitation, Tb 3+ at the B site yielded a larger splitting of the main PL peak at 545 nm ( 5 D 4 – 7 F 5 transitions) than Tb 3+ at the A site. In addition, Tb 3+ at the A site gave rise to not only green luminescence but also a weak blue luminescence ( 5 D 3 – 7 F J transitions), while the blue luminescence was quenched for Tb 3+ at the B site.…”