E. V. Koporulina

Efficient 1 W continuous-wave diode-pumped Er,Yb:YAl3(BO3)4 laser

We report the spectroscopy and high-power continuous-wave (CW) diode-pumped laser operation of Er:Yb:YAl3(BO3) crystal. Absorption and stimulated emission spectra, emission lifetimes, and efficiency of energy transfer from Yb3+ to Er3+ ions were determined. A CW Er:Yb:YAB laser emitting at 1602, 1555, and 1531 nm with output power as high as 1W and slope efficiency up to 35% was demonstrated.

Flux growth and luminescence of Ho : YAl3(BO3)4 and PrAl3(BO3)4 crystals

Abstract HoxY1−xAl3(BO3)4 and PrAl3(BO3)4 crystals have been grown from high-temperature solutions. Holmium segregation coefficients ranged from 1.08 to 1.40. Strong visible and near-infrared luminescence from Ho3+ and Pr3+ was obtained in the crystals with only weak-concentration quenching. Spectral evidence of energy transfer among Ho3+ ions was also observed. The simultaneous observations of low-concentration quenching and Ho3+–Ho3+ energy transfer suggest that YAl3(BO3)4 is a suitable host lattice for high-efficiency rare-earth energy transfer and sensitization schemes.

Crystal growth of solid solutions based on the YAl3(BO3)4, NdAl3(BO3)4 and GdAl3(BO3)4 borates

Abstract Single crystals of NdxY1−xAl3(BO3)4 (NYAB) and GdxY1−xAl3(BO3)4 (GYAB) have been grown from fluxed melts based on the potassium trimolybdate by both the TSSG method and spontaneous crystallization. Neodymium and gadolinium are practically uniformly distributed over the entire volume of crystals. The effective segregation coefficients of neodymium and gadolinium were found to be 0.3–0.8 and about 1 for NYAB and GYAB, respectively. In the case of NYAB, this coefficient increases with an increase in crystallization temperature and a decrease in the crystal growth rate. Growth striations are developed on the trigonal prism faces of the NYAB and GYAB crystals enriched by NAB and GAB which tend to form the monoclinic structures.

Crystallization of solid solutions based on double borates with huntite structure

Abstract Single crystals of RE x Y 1− x Al 3 (BO 3 ) 4 (REYAB), where RE=Nd, Gd, Ho, Yb and Lu, have been obtained from fluxed melts based on potassium trimolybdate. The Nd x Gd 1− x Al 3 (BO 3 ) 4 (NGAB) ( x =0.2) have also been grown by top seeded solution growth (TSSG) method. Effective segregation coefficients of rare earth elements were found to be 0.3–1.03, depending on the type of dopant cations. In the case of Nd x Y 1− x Al 3 (BO 3 ) 4 (NYAB), it increases with increasing Nd 2 O 3 /Y 2 O 3 ratio in the initial mixture. The crystal structure of Nd 0.17 Gd 0.83 Al 3 (BO 3 ) 4 was refined.

Flux growth, composition, structural and thermal characteristics of (RxY1−x)Al3(BO3)4 (R=Nd, Gd; x=1, 0.6, 0.65, 0.7 and 0.75) crystals

(R x Y 1-x )Al 3 (BO 3 ) 4 (R = Nd, Gd; x = 1, 0.6, 0.65, 0.7 and 0.75) single crystals have been grown from fluxed melts. The segregation coefficients of neodymium and gadolinium were estimated to be 0.66-0.92 and 0.88-1.03, respectively. This coefficient increases with an increase of R 2 O 3 /Y 2 O 3 ratio in the initial mixture. The (Nd 0.63 Y 0.37 )Al 3 (BO 3 ) 4 structure was refined. The thermal behavior of the above borates was studied in the temperature range of 940-1030°C. Among the decomposition products, the crystalline aluminoborates Al 4 B 2 O 9 , Al 18 B 4 O 33 and rare earth borates RBO 3 were determined.

Surface activation and induced change of physicochemical and process properties of galena by nanosecond electromagnetic pulses

X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy are used to study the change of the surface layers and chemical state of atoms on galena surface after treatment by high-voltage nanosecond electromagnetic pulses. By XPS the induced structural changes of galena surface layer are associated with alteration of chemical state of sulfur atoms, which conditions the change of electrochemical and flotation properties of the semiconductor sulfide mineral: growth of electrode potential creates favorable conditions for adsorption of anion collector and promotes increased floatability of galena.

High-temperature crystallization of novel rare-earth borate materials: Single crystals and thin films

Phase formation has been studied in the complex system YbAl3(BO3)4 – K2Mo3O10 – B2O3 – Yb2O3 within the stability region of YbAl3(BO3)4 (YbAB). The obtained data were compared with those for YAl3(BO3)4 as another end member of the YbAB-YAB solid solutions. Visually transparent (Er,Yb):YAl3(BO3)4 single crystals with a typical size up to 10×10×15 mm3 and crystalline layers were obtained from K2Mo3O10 based fluxed melts. The 1.5 μm emission spectra of (Er,Yb):YAl3(BO3)4 thin films as well as bulk crystals were measured using CW Ti:sapphire laser tuned to 976 nm as a pump source.

Changes in the functional chemical composition of the surfaces and microhardness of kimberlite minerals under the action of nanosecond high voltage pulses

Using a set of physicochemical methods (XPS, analytical electron microscopy, the adsorption of acid–base indicators, and measuring microhardness), the effectiveness of nonthermal action produced by nanosecond high voltage pulses for targeted changes in the phase (functional chemical) composition and technological properties of rock-forming minerals of kimberlites and diamonds is shown. According to data obtained via XPS and SEM-EDX analyses, pulse energy actions damage the surface microstructure of dielectric minerals with the subsequent formation of traces of surface breakdowns and microcracks, softening rockforming minerals, and reducing their microhardness by 40–66% overall. The following changes in the functional chemical composition of a geomaterial surface are established through the adsorption of acid–base indicators: mutual transformations of the Brønsted base, Lewis base, and Brønsted acid sites on a calcite surface under the action of an electromagnetic pulse and the hydroxylation and/or formation of carbonyl groups on a diamond surface, doubling the diamond electrokinetic potential in the negative range.

Flux growth of (Y,RE)Al3(BO3)4 solid solutions (RE=Nd, Gd, Ho, Yb, Lu)

(RE x Y 1-x )Al 3 (BO 3 ) 4 (RE = Nd, Gd, Ho, Yb and Lu) single crystals have been grown from fluxed melts based on potassium trimolybdate. The average RE distribution coefficients were found to be 0.35-1.02 for different rare earth elements. Among these solid solutions, a new polytype (Nd 0.17 Gd 0.83 )Al 3 (BO 3 ) 4 has been obtained.

REEAl2.07(B4O10)O0.60 dimetaborates (REE = La, Pr); synthesis and X-ray structural characterization

Abstract Nonstoichiometric REEAl2.07(B4O10)O0.60 (REE = La, Pr) borates have been crystallized and analyzed by means of single crystal X-ray diffraction. The compounds resulted to be isostructural within hexagonal space group P-62m (n. 189), with the following unit cell parameters: a = 4.6170(1) Å, c = 9.3640(3) Å and V = 172.87(1) Å3 (La); a = 4.5990(1) Å; c = 9.3270(2) Å and V = 170.87(1) Å3 (Pr). REE cations make up a trigonal prismatic coordination, by means of six REE-O bonds under 2.5 Å; aluminium cation is five-coordinated, displaying a square pyramidal coordination, while the boron atom forms BO4 tetrahedral units. The present borates belong to the structural type of NdAl2.07(B4O10)O0.60 dimetaborate [1]: thus, the three-dimensional framework can be described as a structure packed down crystallographic axis c, with layers of six-membered rings of B tetrahedra alternated by inter-layers REE cations and layers of Al polyhedra. An intricate network of Al···O and REE···O interactions complete the array.