Wereport on the dynamics of laser generation during the transition from stable mode-locking to mode-locking accompanied by long period pulsations. In this case, the optical spectrum in the long-period pulsation regime is accompanied by emission in three spectral regions with maximum at three wavelengths: 1562, 1598 and 1623 nm.

The phase diagram of the SrF2–MgF2 system has been studied by differential thermal analysis (DTA) and X-ray powder diffraction (XRD). The stability area of the compound SrMgF4 is very small, and its extent is about 20°С between 870 and 890°С. The formation of compounds by magnesium fluoride and strontium fluoride with other metal fluorides is considered in the M versus X coordinates, where M is the cumulative moment of the cation and X is the cation electronegativity. Two areas of compound formation were identified for each of the fluorides. Magnesium and strontium fluorides are amphoteric compounds in terms of the Lewis acid and base theory.

The phase diagram of the SrF2–MgF2 system has been studied by differential thermal analysis (DTA) and X-ray powder diffraction (XRD). The stability area of the compound SrMgF4 is very small, and its extent is about 20°С between 870 and 890°С. The formation of compounds by magnesium fluoride and strontium fluoride with other metal fluorides is considered in the M versus X coordinates, where M is the cumulative moment of the cation and X is the cation electronegativity. Two areas of compound formation were identified for each of the fluorides. Magnesium and strontium fluorides are amphoteric compounds in terms of the Lewis acid and base theory.

Методом Бриджмена выращены монокристаллические образцы твердых растворов Ca x Sr y Ba z F 2 ( x = 0.31–0.4045, y = 0.31–0.50, z = 0.10–0.38) и Ca x Sr y Ba z Yb 0.005 F 2.005 ( x = 0.295–0.495, y = 0.30–0.50, z = 0.10–0.40) с флюоритовой структурой. Абсолютным стационарным методом продольного теплового потока в интервале 50–300 K исследована их теплопроводность. При комнатной температуре значения коэффициента теплопроводности всех исследованных образцов ниже 2.5 Вт/(м К). Теплопроводность убывает с увеличением содержания тяжелых компонентов в данных твердых растворах. Этот же фактор снижает негативное влияние на теплопроводность добавки гетеровалентной примеси YbF 3 .

— Single crystals of Ca x Sr y Ba z F 2 ( x = 0.31–0.4045, y = 0.31–0.50, z = 0.10–0.38) and Ca x Sr y Ba z Yb 0.005 F 2.005 ( x = 0.295–0.495, y = 0.30–0.50, z = 0.10–0.40) fluorite solid solutions have been grown by the Bridgman technique, and their thermal conductivity has been measured in the range 50–300 K by an absolute steady-state axial heat flow technique. The room-temperature thermal conductivity of all the crystals studied is below 2.5 W/(m K). As the percentage of the heavy components of the solid solutions increases, their thermal conductivity decreases. In addition, this factor reduces the negative effect of the heterovalent dopant YbF 3 on the thermal conductivity of the crystals.

The optical characteristics of Ca0.33Sr0.33Ba0.33F2 (CSBF) single crystal of a ternary solid solution of calcium, strontium and barium fluorides were studied in order to create disordered optical media. Characteristics of the single crystals of individual fluorides CaF2, SrF2, BaF2 and binary solid solutions Ca0.6Sr0.4F2 and Ba0.67Sr0.33F2 were obtained. Broadband reflection and transmission spectra of the said crystals were recorded in the frequency range of 3-5000 cm(-1), and the values of the complex refractive indexes and dielectric constants were calculated. The generalized four parameter model were used for calculation of absorption band parameters. For the CSBF crystal, a significant broadening of the band was observed in the absorption region at optical phonon modes along with an increased absorption in the region below the optical phonon frequencies, which is typical for disordered dielectric media.

Samples of CaF2:D y 3+ crystals and CaF2-SrF2:D y 3+ solid solution were obtained by the Bridgman-Stockbarger method. The spectroscopic characteristics were calculated from the experimentally obtained optical spectra. Using the Judd-Ofelt analysis, intensity parameters 02,4,6 were obtained. On their basis, integral luminescence cross sections, radiative lifetimes, and luminescence branching coefficients in the IR region are calculated. Using the correspondence method, the luminescence spectra of the 6H13/2 -> 6H15/2 transition were obtained

A concentration series of Ca(1 − X)SrXF2:4 mol % YbF3 crystals with Х varying from 0 to 1 has been grown. The absorption spectra of Yb3+ ions in these crystals are measured at temperatures of 300 and 77 K. It is shown that the intensity ratio of the absorption lines of clusters and tetragonal centers in the congruent crystals is higher than that in the other CaF2–SrF2 solid solution crystals. Analysis of the absorption profiles of Yb3+ optical centers in the concentration series of the solid solution crystals shows that it is energetically favorable for the Sr2+ ion to enter the local environment of both the tetragonal center and the cluster.

At the present time the sulfur content in pipe steel is strictly regulated. Under conditions of PJSC “Magnitogorsk Iron and Steel Works” the metal is smelted in BOF shop with preliminary desulfurization of molten iron, treatment of tapping steel by a solid slag-forming mixture and final desulfurization in the “Ladle-Furnace” unit (LP-unit). In order to increase the efficiency of the sulfur removal process, the influence of the covering slag composition on metal desulfurization is considered. Statistical processing of production data array consisting of 14 melts of steel grade 10Г2ФБЮ with K60 strength class was performed. The dependences of the sulfur content in the metal after desulfurization in the LP-unit on the oxidizing ability, covering slag basicity and the content of magnesium oxide was established: it is shown that the amount of sulfur removed during the ladle treatment process increases with the increase of the covering slag basicity and with the decrease of the magnesium oxide content in slag. For describing this dependence, a new parameter was proposed – the ratio of slag basicity to MgO content in it, %–1. A high content of magnesium oxide in the “white” slag was revealed. This fact indicates a significant amount of converter slag getting into the ladle due to its poor cut-off in the process of metal tapping from the unit. The study of the influence of the coating “white” slag composition on the metal desulfurization process in the LP-unit showed, that for the effective sulfur removal, it is necessary to provide not only welldeoxidized slag with a total content of iron and manganese oxides of less than 1%, but also to ensure the ratio of its basicity to the magnesium content in this slag not less than 0.60–0.65%–1.

At the present time the sulfur content in pipe steel is strictly regulated. Under conditions of PJSC “Magnitogorsk Iron and Steel Works” the metal is smelted in BOF shop with preliminary desulfurization of molten iron, treatment of tapping steel by a solid slag-forming mixture and final desulfurization in the “Ladle-Furnace” unit (LP-unit). In order to increase the efficiency of the sulfur removal process, the influence of the covering slag composition on metal desulfurization is considered. Statistical processing of production data array consisting of 14 melts of steel grade 10Г2ФБЮ with K60 strength class was performed. The dependences of the sulfur content in the metal after desulfurization in the LP-unit on the oxidizing ability, covering slag basicity and the content of magnesium oxide was established: it is shown that the amount of sulfur removed during the ladle treatment process increases with the increase of the covering slag basicity and with the decrease of the magnesium oxide content in slag. For describing this dependence, a new parameter was proposed – the ratio of slag basicity to MgO content in it, % –1 . A high content of magnesium oxide in the “white” slag was revealed. This fact indicates a significant amount of converter slag getting into the ladle due to its poor cut-off in the process of metal tapping from the unit. The study of the influence of the coating “white” slag composition on the metal desulfurization process in the LP-unit showed, that for the effective sulfur removal, it is necessary to provide not only welldeoxidized slag with a total content of iron and manganese oxides of less than 1%, but also to ensure the ratio of its basicity to the magnesium content in this slag not less than 0.60–0.65% –1 .

X-ray diffraction studies of crystals CaF 2 -ErF 3 , CaF 2 -YbF 3 , Ca x Sr 1-x F 2 were carried out at various concentrations of rare-earth elements. Phase analysis performed by the data base PDF-2. The structural characteristics of the found phases were refined using the full-profile analysis (Rietveld method). The dependence of the lattice constant on the impurity concentration is revealed.

The absorption spectra of Yb 3+ ions in a concentration series of Ca( 1-X ) Sr X F 2 crystals: 4 mol% YbF 3 were studied with varying X from 0 to 1 at temperatures T=300K and T=77K. The largest peak absorption cross section for the optical centers of Yb 3+ ion clusters is characteristic of congruently melting crystals. The composition regions of CaF 2 -SrF 2 -4 mol.% YbF 3 crystals with the maximum inhomogeneous broadening of spectral lines were determined. The features of the effect of the composition on the dominant optical centers of Yb 3+ ions are revealed.

Three stages of metal desulfurization in a ladle during production of low-sulfur pipe steel grade DNV SAWL 485 FD in the PAO MMK oxygen converter workshop are analyzed: the first stage is the treatment of semiproduct during metal delivery from a converter with solid slag-forming mixture; the second stage is steel processing in a ladle-furnace unit under a “white” slag; the third stage is the injection of fluidized lime into steel in a ladle-furnace unit. The relative amount of sulfur removed at different stages of treatment is compared. The greatest amount of sulfur, i.e., approximately three quarters of the total amount, is removed in the ladle-furnace during the second and third stages in the ratio 1:1.33. Dependences are revealed for the degree of metal desulfurization on the ratio of the lump lime weight to fluorspar weight, the specific consumption of fluidized lime and the intensity of its injection in the argon stream, are revealed for the second and third stages. Rational values are recommended for parameters in order to improve metal ladle desulfurization efficiency.

A new cast iron desulfurization unit is put into operation in the oxygen converter workshop of Magnitogorsk Metallurgical Combine. Statistically significant linear dependences are established for the degree of cast iron desulfurization on nitrogen injection duration, overall weight of fluidized lime and magnesium, and the weight ratio of fluidized lime and magnesium. An average degree of metal desulfurization of 77.3% is achieved in checking the technology for cast iron ladle desulfurization with injection lasting up to 30 min of fluidized lime and magnesium in a stream of nitrogen with specific consumption of 1.9 and 0.4 kg/ton, respectively.

The mechanisms of upconversion luminescence of CaF2:Ho crystals and ceramics from 5F3, 5S2(5F4), 5F5 and 5I6 levels upon excitation of 5I7 level of Ho3+ ions were investigated. Different mechanisms are responsible for the populating and depletion of the energy levels of Ho3+ ion in CaF2:Ho crystals and ceramics upon excitation of 5I7 level. The upconversion luminescence from 5F3, 5F5, and 5I6 levels in CaF2:Ho crystals and ceramics is explained by energy transfer upconversion processes. Our results also confirmed that both excited-state absorption and energy transfer upconversion are responsible for the populating of 5S2(5F4) level.

Yttria-stabilised zirconia crystals are grown by directional crystallisation in a cold container using direct RF melting. The spectral and luminescent properties of these crystals are studied in order to use them as active media of solid state lasers emitting in the wavelength range .

The anti-Stokes luminescence spectra of Ho : CaF2 crystals corresponding to the (5)G(4) -> I-5(8), (5)G(5) -> I-5(8), F-5(3) -> I-5(8), F-5(4)(S-5(2)) -> I-5(8), F-5(5) -> I-5(8), S-5(2) -> I-5(7), I-5(4) -> I-5(8), I-5(5) -> I-5(8), F-5(5) -> I-5(7), F-5(3) -> I-5(6), I-5(6) -> I-5(8), F-5(5) -> I-5(6), and I-5(5) -> I-5(7) transitions upon excitation of the I-5(7) level of Ho3+ ions are studied. A method for visualisation of IR radiation in the two-micron range using Ho:CaF2 crystals is proposed. The energy efficiency of conversion of two-micron laser radiation to radiation in the red spectral range 620-690 nm by a 1 mol % HoF3:CaF2 crystal is estimated to be no higher than 0.02 %.

The spectral dependences of the gain cross section of the I-5(8) -> I-5(7), I-5(7) -> I-5(8) transition of Ho3+ ions in the ZrO2-13.6 mol % Y2O3-0.4 mol % Ho2O3 crystal are calculated at different relative population inversions using the absorption and luminescence spectra of the I-5(8) -> I-5(7) and I-5(7) -> I-5(8) transitions of Ho3+ ions at T = 300 K. Lasing of these crystals at the I-5(7) -> I-5(8) transition is obtained for the first time under pumping by a Tm : YLiF4 laser (lambda(p) = 1.905 mu m). The lasing wavelength is 2.17 mu m.