—
We have studied optical absorption and luminescence in fluorozirconate glasses activated with manganese, which was added to the glass batch in the form of compounds of manganese in different ...valence states (Mn
2+
and Mn
4+
). The results demonstrate that, independent of its original valence state, the manganese is present in the glasses as Mn
2+
and Mn
3+
ions. The 300-K luminescence spectrum of the fluoride glass contains a broad green emission band due to the Mn
2+
4
T
1
(
G
) →
6
A
1
transition. Its absorption spectrum contains weak bands due to Mn
2+
and a relatively strong, broad band of Mn
3+
. Partial chlorine substitution for fluorine leads to a redshift of the luminescence bands and absorption band of manganese. The changes induced in the spectra by chlorine substitution for fluorine are due to changes in the local environment of the manganese ions.
Fluorozirconate glasses, including those with partial replacement of fluorine by chlorine in the composition, doped with MnO
2
and K
2
MnF
6
, have been synthesized, and their optical absorption and ...EPR have been studied. The EPR data demonstrate the absence of isolated Mn
4+
ions in the samples. The absorption spectra arise from Mn
2+
and Mn
3+
ions, which are formed because of the reduction of Mn
4+
ions introduced with MnO
2
and K
2
MnF
6
activators. It has been found that the replacement of fluorine by chlorine is accompanied by an increase in the relative concentration of Mn
3+
in glass.
A concentration series of (Pb
0.67
Cd
0.33
)
1 –
x
Mn
x
F
2 +
х
(0 ≤
x
≤ 0.7) solid solution crystals and Cd
0.93
Mn
0.07
F
2
crystal have been grown from melt by the vertical directional melt ...crystallization (Bridgman) method in a fluorinating atmosphere. Single-phase crystals with the fluorite structure are obtained by doping Pb
0.67
Cd
0.33
F
2
with manganese fluoride up to 5 mol %. At higher MnF
2
contents in the crystals, the tetragonal impurity phase, isostructural to the Ba
2
M
F
6
(
M
= Mn, Co, Zn) group of compounds, is precipitated. The optical absorption and luminescence of the Cd
0.93
Mn
0.07
F
2
and (Pb
0.67
Cd
0.33
)
0.95
Mn
0.05
F
2
crystals have been investigated. The absorption spectra indicate octahedral symmetry of the environment of Mn
2+
ions in the ternary crystal (Pb
0.67
Cd
0.33
)
0.95
Mn
0.05
F
2
. The wide Mn
2+
luminescence band in (Pb
0.67
Cd
0.33
)
0.95
Mn
0.05
F
2
, peaking at 605 nm, is observed only at 77 K.
—
We have studied luminescence and electron paramagnetic resonance (EPR) spectra of manganese- and europium-activated fluorozirconate glasses in the ZrF
4
–BaF
2
–LaF
3
–AlF
3
–NaF (ZBLAN) system and ...fluorohafnate glasses in the HfF
4
–BaF
2
–LaF
3
–AlF
3
–NaF (HBLAN) system in order to assess the oxidation state and spatial distribution of the activator ions. The manganese luminescence band has been shown to shift from the green (545 nm) to the red (610 nm) spectral region, and additional lines in the EPR spectrum of manganese have been observed to emerge in the EPR spectrum of manganese as a result of BaCl
2
substitution for BaF
2
in the ZBLAN glass. The ratio of the concentration of free activator ions to that of clustered ions has been estimated quantitatively. It has been shown that, at high doping levels, the manganese and europium ions in the glasses are predominantly clustered, and only a small part of them are present as isolated ions.
Crystals of the concentration series ZrO
2
–(8–10) mol % Sc
2
O
3
–(1–2) mol % Tb
2
O
3
were grown by the method of directional crystallization of the melt from a cold container. Analysis of the ...spectral-luminescence characteristics of these crystals after growth and after annealing processing in a vacuum revealed the presence of both Tb
3+
and Tb
4+
ions in them. In crystals ZrO
2
–(8–10) mol % Sc
2
O
3
–(1–2) mol % Tb
2
O
3
, the presence of a process of non-radiative energy transfer from Tb
4+
ions to Tb
3+
ions was revealed.
Chromium trifluoride-doped fluoride glasses in the ZrF
4
–BaF
2
–LaF
3
–AlF
3
–NaF (ZBLAN) system with partial substitution of fluorine for chlorine have been synthesized. The spectral data obtained ...confirm that chromium ions enter the glass structure and exhibit broadband luminescence caused by the
4
T
2
→
4
A
2
transition in the Cr
3+
ion. The observed long-wavelength shift of the broadband luminescence band and Cr
3+
absorption bands in fluoride–chloride glass compared to fluoride glass corresponds to the expected behavior of the Cr
3+
luminescence and absorption spectra when fluoride ions are replaced by chloride ions, which should lead to a weakening of the strength of the crystal field acting on Cr
3+
ions. At room temperature, the luminescence of Cr
3+
ions at 888 and 908 nm is strongly quenched due to the thermally stimulated nonradiative transition from the
4
T
2
excited state to the
4
A
2
ground state.
The EPR and luminescence spectra of fluorozirconate and fluorochlorozirconate glasses doped with various manganese compounds were studied to determine the oxidation state of manganese ions and the ...structure of their distribution. The luminescence spectra of both the fluorozirconate and the fluorochlorozirconate glasses showed the presence of only Mn
2+
ions due to the
4
T
1
(
G
) →
6
A
1
transition, regardless of the oxidation state of the manganese ions in the initial dopant compound. In the fluorozirconate glasses, Mn
2+
ions have a green emission band at 550 nm, which is shifted to the red region to 615 nm after the substitution of chlorine for a part of the fluorine in the glass. The ratio of the content of free manganese ions to the content of ions in clusters in the synthesized glasses was investigated. It was determined that manganese ions in the glasses are mainly aggregated to form clusters, and an increase in the activator concentration leads to a decrease of the fraction of free ions. The differences in luminescence and EPR spectra between the fluorozirconate and fluorochlorozirconate glasses are explained by a change in the structure of the local environment of the manganese ions.
We have studied the optical absorption, luminescence, and electron paramagnetic resonance of EuF
3
- and EuF
2
-activated fluorohafnate glasses. The glasses prepared with EuF
2
contain both di- and ...trivalent europium. The fraction of divalent europium clusters in the glass host decreases with decreasing EuF
2
concentration. Eu
2+
luminescence in the fluorohafnate glasses is quenched, which is due the overlap of Eu
2+
excited state levels with the conduction band of the glass, resulting in nonradiative relaxation through Hf
3+
levels in the conduction band. The Eu
3+
luminescence spectra contain lines corresponding to transitions from several levels of the
5
D
multiplet to levels of the
7
F
multiplet. The relationship between transitions from different
5
D
levels depends on europium concentration and temperature.
—
We have studied luminescence and electron paramagnetic resonance (EPR) spectra of manganese-activated fluorozirconate glasses. In ZrF
4
–BaF
2
–LaF
3
–AlF
3
–NaF (ZBLAN) glasses, manganese gives a ...green luminescence band peaking at 545 nm. Partial chlorine substitution for fluorine in the glass leads to a shift and broadening of the luminescence band. Complete BaCl
2
substitution for BaF
2
in ZBLAN〈Cl〉 fluoride chloride glass increases the peak emission wavelength to 610 nm. The observed distinctions between the EPR spectra of the Mn-doped ZBLAN and ZBLAN〈Cl〉 glasses correlate with those between their luminescence spectra. The effect of chlorine substitution for fluorine on the luminescence and EPR spectra of the fluorozirconate glass is tentatively attributed to a change in the oxidation state of the manganese ions.
—
We have prepared ErF
3
-doped glasses in the ZrF
4
–BaF
2
–LaF
3
–AlF
3
–NaF system containing chlorine ions substituted for fluorine ions. The crystallization behavior of the chlorine-substituted ...glasses has been studied at various BaCl
2
and ErF
3
concentrations. We have identified phases precipitating during heat treatment of the glasses and assessed the effect of chlorine substitution for fluoride on the optical absorption and IR luminescence in the glasses. The results demonstrate that chlorine substitution for fluorine causes the UV absorption edge of the glass to shift to longer wavelengths and produces an additional absorption in the visible spectral region. The formation of crystalline phases during heat treatment of the glasses leads to significant changes in the shape of the Er
3+
luminescence bands at 0.98 and 1.55 μm.
