A series of fluorochlorozirconate glasses doped with manganese ions is synthesized and investigated as possible red‐emitting phosphors in comparison with conventional green‐emitting fluorozirconate ...glasses doped with Mn2+. It is found that the replacement of fluorine by chlorine ions results in broadening and a long‐wavelength shift of the manganese luminescence band into the red region (peaked at 615 nm) although the emission spectrum still has some contribution of the green sub‐band. It turns out also that decay kinetics of luminescence from fluorochlorozirconate glasses becomes nonexponential in contrast to single‐exponential decay observed for green luminescence from Mn2+‐doped fluorozirconate glasses. The observation of two emission components in the luminescence spectrum of fluorochlorozirconate glasses is interpreted as being due to the presence of two Mn2+ emission centers in different local environments. The presence of 2+ valence states of manganese ions in both types of glasses is confirmed by recording X‐ray absorption near edge structure (XANES) spectra at Mn L2,3 edge. Substitution of F− by Cl− ions in anion sites neighboring to Mn2+, leads to a significant rearrangement of the local environment of Mn2+ ions, which results in the long‐wavelength shift of Mn2+ emission spectrum.
Fluorochlorozirconate glasses doped with manganese ions are proposed as broadband green–red‐emitting phosphors for white light‐emitting diodes (LEDs). The replacement of F− by Cl− ions in fluorozirconate glass host results in the shift of Mn2+ emission spectrum caused by the 4T1–6A1 transition from the green region (λmax ≈ 545 nm) to the red one (λmax ≈ 615 nm).
Features of Methods to Produce High-Purity Arsenic Fedorov, V. A.; Menshchikova, T. K.; Nikonov, K. S. ...
Theoretical foundations of chemical engineering,
08/2023, Letnik:
57, Številka:
4
Journal Article
Recenzirano
This review surveys patent information and fundamental literature sources on the technological foundations of producing high-purity arsenic and its compounds in the leading countries: Russia (USSR), ...USA, Japan, Germany, and China. The 1960–1979 literature sources on the following issues are summarized:—recovery of elemental arsenic from various raw materials;—production of high-purity (99.99999 wt %) arsenic and its compounds;—devices and equipment for recovery and purification of elemental arsenic and arsenic-containing substances.
This paper reports results of studies aimed at developing physicochemical principles of the preparation of high-purity arsenic (99.9999 (6N) and 99.99999 wt % (7N) purity) from standard (As
2
S
3
and ...As
4
S
4
sulfide ores) and unconventional raw materials (lewisite disposal (detoxification) products, nonferrous metals industry waste, and III–V semiconductor fabrication waste). We present data on the behavior of impurities in arsine ultrapurification processes and substantiate integrated approaches to the preparation of high-purity arsine and arsenic from various raw materials.
We have studied electron paramagnetic resonance spectra of europium- and gadolinium-activated ZBLAN-type fluorohafnate glasses, using the composition 58HfF
4
· 20BaF
2
· 2LaF
3
· 3AlF
3
· 17NaF as an ...example. The ratio of the concentration of free Eu
2+
and Gd
3+
ions to that of ions in clusters has been quantitatively evaluated for the first time. The percentage of free ions has been shown to increase significantly with decreasing activator concentration. At activator concentrations of 1.25 mol % EuF
2
and 1 mol % GdF
3
, the activator ions predominantly form clusters and only a small fraction of Eu
2+
and Gd
3+
are present as individual ions, whereas at 0.1 mol % EuF
2
the concentration of free ions is comparable to that of ions in the clusters.
Display omitted
The nuclear quadrupole resonance (NQR) spectroscopy was used to control the comparative purity of three SnCl4 samples subjected to successive stages of deep purification. The results ...showed that at 77 K the samples were identical in purity degree due to the ‘freezing’ of impurities into a separate fraction not affecting the perfection of the SnCl4 crystal lattice. The results of relaxation measurements suggest that paramagnetic impurity atoms (Fe and Cr) contained in the samples in small amounts might be embedded into the crystal lattice causing extremely long spin–spin relaxation time.
This paper reports results of studies aimed at developing physicochemical and technological principles of the preparation of ultrapure, 99.99999 wt % (7N) arsenic from standard (As
2
S
3
sulfide ore) ...and unconventional raw materials (lewisite warfare detoxification products) using directional solidification as a final step in the arsenic ultrapurification process. Using different purification processes, we have obtained and investigated experimental batches of high-purity arsenic.
A technique has been developed for fluorinating the pyrochlore oxide Bi
1.8
Fe
0.2
FeSbO
7
, and a compound with the composition Bi
1.8
Fe
1.2
SbO
7–x/2
F
x
has been obtained. The synthesized ...oxyfluoride also has the pyrochlore structure (sp. gr.
Fd
3
m
), with a lattice parameter a = 10.4443(1) Å (
R
wp
= 5.2). It has been shown that the charge balance upon fluorine substitution for oxygen is maintained not through partial reduction of Fe
3+
to Fe
2+
but through the incorporation of fluorine into oxygen vacancies. The magnetic behavior of the fluorinated pyrochlore phase is determined by the persisting frustration of the octahedral sublattice, which is responsible for the development of a spin glass state below
T
f
= 12 K. The fluorination-induced changes in the anion sublattice led to an increase in the antiferromagnetic exchange interaction between neighboring Fe
3+
ions and changes in the dynamic properties of the spin glass phase.
—
This paper presents results of analysis of the patent, scientific, and technical literature concerned with the physicochemical and technological foundations of the preparation of high-purity ...arsenic-containing compounds from various raw materials. Considerable attention is paid to processing of unconventional raw materials (lewisite detoxification products, nonferrous metals industry waste, and III–V semiconductor materials fabrication waste). Arsenic-containing substances (elemental arsenic, arsenic trichloride, arsenic trioxide, and arsine) containing less than 1 ppm by weight of regulated impurities have been prepared and characterized.
—
A process has been proposed for ZrSe
2
crystal growth with the use of ZrOCl
2
as a transport agent source. The crystals thus grown have been characterized by X-ray diffraction. It has been shown ...that, unlike in the case of vanadium and molybdenum diselenides, the use of zirconium chloride causes no increase in crystal size. A mechanism of the chemical vapor transport process involved is proposed.
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