scholarly journals The growth of sapphire single crystals

2001 ◽  
Vol 66 (6) ◽  
pp. 411-418 ◽  
Author(s):  
Aleksandar Golubovic ◽  
Slobodanka Nikolic ◽  
Stevan Djuric ◽  
Andreja Valcic
Keyword(s):  
Crystal Growth ◽  
Single Crystals ◽  
Powder Diffraction ◽  
Chemical Polishing ◽  
Published Data ◽  
Czochralski Technique ◽  
Critical Rate ◽  
Etching Solution ◽  
X Ray ◽  
Crystal Diameter

Sapphire (Al2O3) single crystals were grown by the Czochralski technique both in air and argon atmospheres. The conditions for growing sapphire single crystals were calculated by using a combination of Reynolds and Grash of numbers. Acritical crystal diameter dc = 20 mm and the critical rate of rotation c = 20 rpm were calculated from the hydrodynamics of the melt. The value of the rate of crystal growth was experimentally found to be 3.5 mm/h. According to our previous experiments, it was confirmed that three hours exposures to conc. H3PO4 at 593 K was suitable for chemical polishing. Also, three hours exposure to conc.H3PO4 at 523Kwas found to be a suitable etching solution. The lattice parameters a = 0.47573 nm and c = 1.29893 nm were determined by X-ray powder diffraction. The obtained results are discussed and compared with published data.

scholarly journals The growth of ruby single crystals

2005 ◽  
Vol 70 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Aleksandar Golubovic ◽  
Slobodanka Nikolic ◽  
Stevan Djuric ◽  
Andreja Valcic
Keyword(s):  
Crystal Growth ◽  
Single Crystals ◽  
Powder Diffraction ◽  
Argon Atmosphere ◽  
Published Data ◽  
Czochralski Technique ◽  
Critical Rate ◽  
Etching Solution ◽  
X Ray ◽  
Crystal Diameter

Ruby (Cr:Al2O3) single crystals were grown by the Czochralski technique in an argon atmosphere. The critical crystal diameter dc = 1.0 cm and the critical rate of rotation ?c = 20 rpm were calculated by equations of the hydrodynamics of the melt. The rate of crystal growth was experimentally obtained to be 2.7 mm/h. For chemical polishing, conc. H3PO4 at 593 K for an exposure of 3 hours was determined. Conc. H3PO4 at 523 K for an exposure of 3 h was found to be a suitable etching solution. The lattice parameters a = 0.47627(6) nm and c = 1.301(1) nm were determined by X-ray powder diffraction. The obtained results are discussed and compared with published data.

scholarly journals The growth of Nd: YAG single crystals

2002 ◽  
Vol 67 (4) ◽  
pp. 291-300 ◽  
Author(s):  
Aleksandar Golubovic ◽  
Slobodanka Nikolic ◽  
Rados Gajic ◽  
Stevan Djuric ◽  
Andreja Valcic
Keyword(s):  
Crystal Growth ◽  
Single Crystals ◽  
Powder Diffraction ◽  
Lattice Parameter ◽  
Argon Atmosphere ◽  
Published Data ◽  
Czochralski Technique ◽  
Critical Rate ◽  
X Ray ◽  
Crystal Diameter

Y3Al5O12 doped with 0.8%wt.Nd (Nd:YAG) single crystals were grown by the Czochralski technique under an argon atmosphere. The conditions for growing the Nd:YAG single crystals were calculated by using a combination of Reynolds and Grashof numbers. The critical crystal diameter and the critical rate of rotation were calculated from the hydrodynamics of the melt. The crystal diameter Dc=1.5 cm remained constant during the crystal growth while the critical rate of rotation changed from ?c=38 rpm after necking to ?c=13 rpm at the end of the crystal. The value of the rate of crystal growth was experimentally found to be 0.8?1.0 mm/h. According to our previous experiments, it was confirmed that 20 min exposure to conc. H3PO4 at 603 K was suitable for chemical polishing. Also, one-hour exposure to conc. H3PO4 at 493 K was found to be suitable for etching. The lattice parameter a=1.201 (1) nm was determined by X-ray powder diffraction. The obtained results are discussed and compared with published data.

scholarly journals The growth and optical properties of Bi12SiO20 single crystals

2002 ◽  
Vol 67 (4) ◽  
pp. 279-289 ◽  
Author(s):  
Aleksandar Golubovic ◽  
Slobodanka Nikolic ◽  
Rados Gajic ◽  
Stevan Djuric ◽  
Andreja Valcic
Keyword(s):  
Crystal Growth ◽  
Single Crystals ◽  
Lattice Parameter ◽  
Published Data ◽  
Czochralski Technique ◽  
Critical Rate ◽  
X Ray ◽  
Wave Numbers ◽  
Different Temperatures ◽  
Crystal Diameter

Single crystals of Bi12SiO20 were grown from the melt by the Czochralski technique. The critical crystal diameter dc=10 mm and the critical rate of rotation ?c=20 rpm were calculated by equations from the hydrodynamics of a melt. The rate of crystal growth was experimentally obtained to be 5 mm/h. The crystal growth was in the [111] direction. The lattice parameter a=1.0096nm was determined by X-ray powder diffraction. The reflectance spectra were recorded in the wave numbers range 20?5000 cm-1 at different temperatures. For all the recorded spectra the values of the vibrational TO and LO modes were found using the Kramers-Kronig analysis (KKA). Twentyfive TO and LO modes were found at 70 K, and eighteen at 295 K. The obtained results are discussed and compared with published data.

scholarly journals Pb1-xMnxTe single crystals and their structural properties

2004 ◽  
Vol 69 (12) ◽  
pp. 1121-1128 ◽  
Author(s):  
Aleksandar Golubovic ◽  
Slobodanka Nikolic ◽  
Stevan Djuric ◽  
Nebojsa Romcevic
Keyword(s):  
Diffraction Analysis ◽  
Single Crystals ◽  
Structural Properties ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Chemical Polishing ◽  
Published Data ◽  
Etching Solution ◽  
X Ray ◽  
Vertical Bridgman

Pb1-xMnxTe crystals were grown by the vertical Bridgman method. Their structural properties were observed both by optical microscopy after chemical polishing and ething, and by X-ray powder diffraction analysis. A solution of 5 vol. % Br2 in HBr at room temperatur, for an exposure of 2 min was determined for chemical polishing. Asolution of 20 g KOH in 1 ml H2O2, 2 ml glycerol (C3H8O3), and 20 ml H2O at room temperature for an exposure for 6 min was found to be a suitable etching solution. The obtained results are discussed and compared with published data.

scholarly journals The growth of Nd:CaWO4 single crystals

2003 ◽  
Vol 68 (12) ◽  
pp. 1001-1009 ◽  
Author(s):  
Aleksandar Golubovic ◽  
Slobodanka Nikolic ◽  
Rados Gajic ◽  
Stevan Djuric ◽  
Andreja Valcic
Keyword(s):  
Single Crystals ◽  
Room Temperature ◽  
Chromic Acid ◽  
Critical Diameter ◽  
Published Data ◽  
Hydrodynamic Equations ◽  
Czochralski Technique ◽  
Critical Rate ◽  
X Ray ◽  
C 30

CaWO4 doped with 0.8 % at. Nd (Nd:CaWO4) single crystals were grown from the melt in air by the Czochralski technique. The critical diameter dc = 1.0 cm and the critical rate of rotation ?c = 30 rpm were calculated from hydrodynamic equations for buoyancy-driven and forced convection. The rate of crystal growth was experimentally obtained to be 6.7 mm/h. For chemical polishing, a solution of 1 part saturated chromic acid (CrO3 in water) and 3 parts conc. H3PO4 (85 %) at 433 K with an exposure time of 2 h was found to be adequate. A mixture of 1 part concentrated HF and 2 parts chromic acid at room temperature after exposure for 30 min was found to be a suitable etching solution. The lattice parameters a = 0.52404 (6) nm, c = 1.1362 (6) nm and V0 = 0.312 (2) nm3 were determined by X-ray powder diffraction. The obtained results are discussed and compared with published data.

scholarly journals Phonon anomalies in optical spectra of LnNbO3 single crystals

2004 ◽  
Vol 69 (6) ◽  
pp. 493-502 ◽  
Author(s):  
Aleksandar Golubovic ◽  
Rados Gajic ◽  
Ivana Hinic ◽  
Andreja Valcic
Keyword(s):  
Single Crystals ◽  
Published Data ◽  
Czochralski Technique ◽  
Phonon Modes ◽  
Critical Rate ◽  
Air Atmosphere ◽  
Domain Structures ◽  
Infrared And Raman Spectroscopy ◽  
Crystal Diameter ◽  
Domain Inversion

LiNbO3 single crystals were grown by the Czochralski technique in an air atmosphere. The critical crystal diameter Dc = 1.5 cm and the critical rate of rotation ?c=35 rpm were calculated by equations from the hydrodynamics of the melt. The domain inversion was carried out at 1430 K using a 3.75 V/cm electric field for 10 min. The obtained crystals were cut, polished and etched to determine the presence of dislocations and single domain structures. The optical properties were studied by infrared and Raman spectroscopy as a function of temperature. With decreasing temperature, an atypical behaviour of the phonon modes could be seen in the ferroelectrics LiNbO3. The obtained results are discussed and compared with published data.

scholarly journals Single crystals of bismuth silicon oxide grown by the czochralski technique and their characterisation

1999 ◽  
Vol 64 (9) ◽  
pp. 553-561 ◽  
Author(s):  
Aleksandar Golubovic ◽  
Slobodanka Nikolic ◽  
Rados Gajic ◽  
Stevan Djuric ◽  
Andreja Valcic
Keyword(s):  
Optical Properties ◽  
Single Crystals ◽  
Silicon Oxide ◽  
Critical Diameter ◽  
Lattice Parameters ◽  
Published Data ◽  
Czochralski Technique ◽  
Critical Rate ◽  
Bismuth Silicon Oxide ◽  
X Ray

Single crystals of Bi12SiO20 were grown by the Czochralski technique. The critical diameter and the critical rate of rotation were calculated. Suitable polishing and etching solutions were determined. X-Ray measurements were performed on powdered samples to obtain the lattice parameters. The optical properties of the bismuth silicon oxide single crystals were investigated. The obtained results are discussed and compared with published data.

scholarly journals The growth of Mg2TiO4 single crystals using a four-mirror furnace

2011 ◽  
Vol 76 (11) ◽  
pp. 1561-1566 ◽  
Author(s):  
Aleksandar Golubovic ◽  
Marko Radovic
Keyword(s):  
Optical Properties ◽  
Single Crystal ◽  
Diffraction Analysis ◽  
Single Crystals ◽  
Powder Diffraction ◽  
Spectroscopic Ellipsometry ◽  
Lattice Parameter ◽  
Published Data ◽  
X Ray ◽  
Float Zone

A single crystal of Mg2TiO4 was grown by the travelling solvent float zone (TSFZ) method. The lattice parameter a = 0.8444(8) nm was determined by X-ray powder diffraction analysis. The optical properties of the Mg2TiO4 single crystals were studied using spectroscopic ellipsometry. The obtained results are discussed and compared with published data.

Lead Germanate Pb5Ge3O11 Crystal Growth

2018 ◽  
Vol 284 ◽  
pp. 194-197
Author(s):  
D.A. Vinnik ◽  
Vladimir E. Zhivulin ◽  
S.A. Gudkova
Keyword(s):  
Crystal Growth ◽  
Curie Temperature ◽  
Single Crystals ◽  
Czochralski Technique ◽  
Lead Germanate ◽  
X Ray Diffraction ◽  
X Ray

Single crystals of lead germanate are obtained by the Czochralski technique. The dimensions of hexagonally shaped crystals are up to 25 × 25 × 5 mm3. According to X-ray diffraction measurements the grown crystals respond to lead germanate Pb5Ge3O11 structure. Curie temperature was also measured.

scholarly journals The optical properties of LiNbO3 single crystals obtained in air atmosphere

1999 ◽  
Vol 64 (10) ◽  
pp. 637-646 ◽  
Author(s):  
Aleksandar Golubovic ◽  
Slobodanka Nikolic ◽  
Rados Gajic ◽  
Stevan Djuric ◽  
Aleksandar Jelisijevic ◽  
...  
Keyword(s):  
Optical Properties ◽  
Single Crystals ◽  
Optical Constants ◽  
High Temperature Superconductor ◽  
Critical Diameter ◽  
Published Data ◽  
Critical Rate ◽  
X Ray ◽  
Air Atmosphere ◽  
Reflectance Data

Single crystals of LiNbO3 were grown by the Czochralski technique in an air atmosphere. The critical diameter and the critical rate of rotation were calculated. X-Ray measurements of the powder were carried out to obtain the lattice parameters.The optical constants were calculated by Kramers-Kronig analysis of reflectance data. The optical properties of LiNbO3 single crystals were studied for samples grown in an air atmosphere to investigate the influence of air on the optical properties of the formed crystals. A peak due to OH. gtroups appears in the transmission spectrum at 3385 cm -1. It was still present after annealing in an air atmosphere at temperature up to 873 K, but it was no longer detectable after annealing at 1473 K in an electric field. Thick films of the high-temperature superconductor YBa2Cu3O7 (Ag) were obtained on plates of LiNbO3 single crystals. The obtained results are discussed and compared with published data.

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