Photoluminescence of KZnF₃:Tl and KMgF₃:Tl crystals

Abstract

The luminescence spectra of KZnF3:Tl+ and KMgF3:Tl+ crystals with a perovskite structure were investigated in the temperature range of 4.2–300 K and at optical excitation in the A absorption band (∼6 eV). The spectrum of KZnF3:Tl+ at 300 K is a wide band with the maximum Emax at 5.48 eV and the width of about 0.47 eV. At 100 K the band splits into two components: an intensive one with Emax = 5.63 eV and a width of about 0.2 eV and a weak one with Emax = 4.66 eV. At 4.2 K an intensive broad band practically disappears and a narrow line accompanied by a vibration structure is observed at E = 5.725 eV. This line is assigned to a zero-phonon transition from the metastable 3 Γ 1u level to the ground 1 Γ 1g level, weakly allowed due to the hyperfine interaction and phonon-assisted mechanisms. The spectrum of KMgF3:Tl+ at 300 K is a band with the maximum at 5.78 eV and a width of about 0.3 eV. This band does not disappear at 4.2 K; its maximum shifts to higher frequencies (5.91 eV) and an intensive narrow line at 5.812 eV is observed on its background. The temperature-dependent luminescence decay was also investigated. At T = 10 K the lifetime of the slow component of luminescence is τs = 11.6 ms for KZnF3:Tl+ and τs = 14.9 ms for KMgF3:Tl+. The main features of the observed luminescence spectra are satisfactorily explained within the framework of the conventional theory, as a manifestation of the Jahn–Teller effect for the excited 6sp electron configuration of an admixture Tl+ ion, with a set of model parameters close to that used earlier to describe absorption spectra of the studied crystals.

Optical studies of Pb2+ions in a LiBaF3crystal

“…The A band luminescence decay of the ns 2 -ions in cubic surroundings has in general two components-fast and slow [1,2,7]. Our investigations have shown that the integral intensity of the fast luminescence is less than 1% of that for the slow one.…”

“…Our interest concerns fluoride crystals with the perovskite structure, where ns 2 -ions are located in a 12-fold fluorine surrounding. Previously, we have studied the absorption and luminescence of Tl + ions in KZnF 3 and KMgF 3 crystals [6,7]. In spite of the great similarity of the host lattices the luminescent properties of these crystals differ significantly.…”

“…Within the frame of this work, pure and Pb 2+ -doped LiBaF 3 single crystals were grown. Absorption and luminescence spectra as well as luminescence decay were studied in the temperature range 10-300 K. As the Pb 2+ ion replaces the Ba 2+ ion in the lattice there is no need for charge compensation, and the theory developed earlier [6,7] to explain the luminescent properties of the KZnF 3 :Tl + and KMgF 3 :Tl + systems was readily applied to the LiBaF 3 :Pb 2+ crystal.…”

VUV and UV spectroscopy of ns2 ions co-doped with Tb3+ ion in Ln(BO2)3 (Ln=La, Gd)

“…Table 1 shows the position of the A-C excitation bands, obtained from Figs. 1 and 2, together with those reported for KMF 3 :Tl + (M ¼ Zn, Mg) [13]. Parameter R, which defines the mixing of spin singlet and triplet states by the spin-orbit interaction, was estimated as 3.7 for La(BO 2 ) 3 : Tl + when the absorption of the polyborate anions was ignored.…”

Synthesis of KZnF\(_{3}\) Phosphors by Co-Precipitation Method

“…Photoluminescence and/or magnetic properties of 3d n ions like Mn 2+ [3,27,40], Mn 4+ [19], Ni 2+ [28,48], Co 2+ [5,45], Cr 3+ [49], Cr 2+ [14,31], Cu 2+ [12], 4f n lanthanides like Yb 3+ [4,25,39], Tm 3+ [41], Dy 3+ [15], Ce 3+ , Eu 2+ [20], Eu 3+ [34], Tb 3+ [9] and ns 2 ion Tl + [2] have been studied quite extensively. KZnF 3 :Tl + is of interest as a promising material for tunable lasers in the UV region [1] and scintillator [2] while KZnF 3 :Co 2+ serves similar purpose in mid infrared region [7,23,33]. Upconversion involving various ion pairs such as Yb 3+ -Mn 2+ [43], Yb 3+ -Er 3+ [22,44], Yb 3+ -Tm 3+ [41], Yb 3+ -Ho 3+ [6], KZnF 3 shows intrinsic luminescence [42] though it does not show any cross-luminescence [10].…”