M. B. Kosmyna

Growth and characterization of Ca9Ln(VO4)7 crystals (Ln = Y, La, or Gd)

Ca9Ln(VO4)7 single crystals (Ln = Y, La, or Gd) have been grown by the Czochralski method. The grown crystals deviate from the stoichiometric ratio Ca/Ln; this deviation increases in the series from Y to Gd.

Peculiarities of the growth of PbWO4:Nd3+ and PbMoO4:Nd3+ single crystals

The dependence of the Nd segregation coefficient on Nd concentration in PbWO4 and PbMoO4 melts and on the method of its introduction is analyzed. In a study of the PbMoO4-Nd2(MoO4)3 pseudobinary system, the existence of the PbNd4(MoO4)7 compound is established for the first time. Its structure is identified, the melting temperature and character are determined, and a single crystal is grown. The dependences of the damage threshold and anomalous biaxiality angle of PbWO4:Nd3+ and PbMoO4:Nd3+ crystals on the concentration of the activator and the method of its introduction are investigated.

Effect of doping method on the formation of charge-compensating defects in PbMoO4:Nd3+ crystals

PbMoO4:Nd3+ single crystals have been grown using different doping schemes. Their dielectric properties have been studied in the temperature range of 20–550°C at frequencies from 25 to 106 Hz. The activation energies of dielectric relaxation are determined for all samples, and the Nd3+ luminescence decay kinetics is studied. The most realistic models of activator centers in PbMoO4:Nd3+ crystals are proposed based on the optical and dielectric spectroscopy data.

CdWO4 crystal growth and production of a spectrometric detection unit with a large-volume (V ≅ 350 cm3) crystal

Large-volume (V ≅ 350 cm3) CdWO4 single crystals of high optical quality have been grown by the Czochralski method. A scintillation detection unit based on a large CdWO4 crystal has been produced and its characteristics have been studied.

Growth of PbWO4:MeF2(MeF2 = PbF2, BaF2) single crystals and their properties

PbF2-and BaF2-doped PbWO4 crystals have been grown by the Czochralski method. The scintillation characteristics of the grown crystals have been determined. It is shown that introduction of BaF2 leads to an increase in the light yield of PbWO4 crystals by 20%, while PbWO4:PbF2 crystals demonstrate a significant increase in radiation hardness.

Growth of PbWO{sub 4}:MeF{sub 2}(MeF{sub 2} = PbF{sub 2}, BaF{sub 2}) single crystals and their properties

PbF2-and BaF2-doped PbWO4 crystals have been grown by the Czochralski method. The scintillation characteristics of the grown crystals have been determined. It is shown that introduction of BaF2 leads to an increase in the light yield of PbWO4 crystals by 20%, while PbWO4:PbF2 crystals demonstrate a significant increase in radiation hardness.

Broadly tunable Cr:ZnSe laser

In our study we have investigated Cr:ZnSe bulk crystal samples grown by the special Bridgeman method. The Cr2+ ion concentration was 1x1019 cm-3. Cr:ZnSe crystal bulks with a diameter up to 50 mm and a length up to 100 mm were produced. From the bulk the Cr:ZnSe dispersive prism was polished. This Cr:ZnSe dispersive prism was utilized as a laser active material and simultaneously as a wavelength tuning element inside the laser resonator.

Investigation of thermophysical characteristics of SrMoO4 crystals, nominally pure and doped with rare earth ions

Thermophysical characteristics of SrMoO4 crystals (grown by the Czochralski method from intrinsic melts), nominally pure and doped with rare earth ions, have been investigated. The temperature and concentration dependences of the thermal conductivity are obtained for SrMoO4 samples containing Nd3+ (0.28, 0.56, 0.84, and 1.33 at %), Pr3+ (0.01 and 0.41 at %), Ho3+ (0.01 and 0.06 at %), and Ho3+ (0.13 at %) + Tm3+ (0.13 at %) in a temperature range of 50–300 K. The thermal conductivities are measured in the directions parallel and/or perpendicular to the crystal optical axis. The thermal conductivity of nominally pure SrMoO4 at 300 K in the direction perpendicular to the c axis has been found to be 4.2 W/(m K). The introduction of impurities of rare earth metals reduces the thermal conductivity of SrMoO4 crystals. The anisotropy of the thermal conductivity is weak. The measured molar specific heat CP(T) of a nominally pure SrMoO4 crystal is 116.2 J/(mol K) at 300 K. The temperature dependence of the phonon mean free path l(T) in a SrMoO4 crystal is calculated for the temperature range of 80-300 K based on experimental data.

Production of Y3Al5O12 and Y2O3 nanopowders for optical ceramics

The physical and technical conditions for reproducible production of nanodispersed yttrium aluminum garnet (Y3Al5O12, YAG) and yttrium oxide (Y2O3) powders by chemical coprecipitation have been investigated. It is established that the obtained YAG nanopowders have enhanced reactivity, which significantly decreases the temperature range of interaction in the Y2O3-Al2O3 system in comparison with ceramic synthesis. It is shown that vacuum heat treatment may lead to reversible transformation of the YAG crystal structure from cubic to tetragonal.The physical and technical conditions for reproducible production of nanodispersed yttrium aluminum garnet (Y{sub 3}Al{sub 5}O{sub 12}, YAG) and yttrium oxide (Y{sub 2}O{sub 3}) powders by chemical coprecipitation have been investigated. It is established that the obtained YAG nanopowders have enhanced reactivity, which significantly decreases the temperature range of interaction in the Y{sub 2}O{sub 3}-Al{sub 2}O{sub 3} system in comparison with ceramic synthesis. It is shown that vacuum heat treatment may lead to reversible transformation of the YAG crystal structure from cubic to tetragonal.

Production of Y{sub 3}Al{sub 5}O{sub 12} and Y{sub 2}O{sub 3} nanopowders for optical ceramics

The physical and technical conditions for reproducible production of nanodispersed yttrium aluminum garnet (Y3Al5O12, YAG) and yttrium oxide (Y2O3) powders by chemical coprecipitation have been investigated. It is established that the obtained YAG nanopowders have enhanced reactivity, which significantly decreases the temperature range of interaction in the Y2O3-Al2O3 system in comparison with ceramic synthesis. It is shown that vacuum heat treatment may lead to reversible transformation of the YAG crystal structure from cubic to tetragonal.The physical and technical conditions for reproducible production of nanodispersed yttrium aluminum garnet (Y{sub 3}Al{sub 5}O{sub 12}, YAG) and yttrium oxide (Y{sub 2}O{sub 3}) powders by chemical coprecipitation have been investigated. It is established that the obtained YAG nanopowders have enhanced reactivity, which significantly decreases the temperature range of interaction in the Y{sub 2}O{sub 3}-Al{sub 2}O{sub 3} system in comparison with ceramic synthesis. It is shown that vacuum heat treatment may lead to reversible transformation of the YAG crystal structure from cubic to tetragonal.