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1

Czochralski Growth and Properties of Scintillating Crystals

Yoshikawa A., Chani V., Nikl M.

Zeszyty Historyczne Politechniki Warszawskiej

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2014

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z. 16

135--149

EN

The Czochralski method is one of the very few melt growth techniques that are industry friendly when considering the combination of quality, dimensions, and cost of the produced crystals suitable for their commercialization in scintillation detectors. This method is one of the oldest and most developed crystal growth processes regarding an adequate understanding the physical phenomena observed during solidification process and its practical expansion especially in the industrial scale production. It allows controllable formation of single-crystalline cylindrical ingots of various inorganic scintillation materials. The review summarizes recent progress on the Czochralski growth of a number of scintillation materials. The oxide crystals are mainly considered including the Ce and Pr-doped RE3Al5O12, RE = Y, Lu, aluminum garnets and newly discovered ultraeffcient Ce-doped Gd3(Ga,Al)5O12 multicomponent garnet, high density PbWO4 and CdWO4 tungstates, Ce-doped RE2SiO5, RE = Y, Gd, Lu, oxyorthosilicates and (Y,Lu)AlO3 aluminum perovskites and finally the classical Bi4Ge3O12 scintillator. Additionally, the details of the growth of other practically important non-oxide crystals, namely the Ce and Eu-doped LiCaAlF6 neutron and ultraeffcient Ce-doped LaBr3 scintillators, are discussed. The potential of novel micro-pulling down growth method is briefly described in the combinatorial search for new scintillator materials. Selected luminescence and scintillation characteristics including the spectra and decay kinetics, light yield and radiation resistance are also illustrated and overviewed.

2

A Review of the Automation of the Czochralski Crystal Growth Process

Winkler J., Neubert M., Rudolph J.

Zeszyty Historyczne Politechniki Warszawskiej

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2014

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z. 16

123--134

EN

On the occasion of the centennial of the invention of the Czochralski crystal growth process by the Polish scientist Jan Czochralski, a review of selected strategies for the automatic control of this process is given. This review provides a sketch of the fundamental challenges of controlling the Czochralski process and the basic concepts of feedback control. Both early and modern approaches to the control of the Czochralski process are described. The discussion focuses on questions related to feed-forward control, feedback control, and state estimation. The presented methods rely on simple mathematical process models in contrast to the finite element model-based approaches typically used in crystal growth process design and analysis. Such mathematical models motivate both the structure and parameters of the chosen controller. A comprehensive list of references to background literature on this topic completes this survey.

3

Growth velocities and sectorial and zonal distributions of impurities in crystals

Szurgot M.

Scientific Bulletin. Physics / Lodz University of Technology

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2010

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Vol. 31

75-86

EN

Formulae for relative impurity content in various parts of a crystal have been derived and analysis of sectorial and zonal distributions of impurities conducted. Contribution of volume diffusion controlled crystal growth for sectorial and tonal distributions of impurities in lopezite crystals has been evaluated as small in comparison with surface diffusion.

PL

Analizowano rozkład zanieczyszczeń w kryształach, wprowadzając nowe zależności na zawartość zanieczyszczeń w różnych częściach kryształów, które wyprowadzono wykorzystując równanie Burtona-Prima-Slichtera. Porównanie zawartości domieszek określonych teoretycznie z danymi eksperymentalnymi gęstości klasterów defektów punktowych w różnych sektorach i prążkach domieszkowych kryształów lopezytu pokazuje, że dla lopezytu wkład dyfuzji objętościowej jest mały i uwzględnienie procesów dyfuzji powierzchniowej jest konieczne.

4

Estimation of surface supersaturation in Monte Carlo simulations of single crystal growth

Rak M., Brozi A., Żmija J.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 41, nr 1-2

91-95

EN

Purpose: The aim of this study is to propose a new calculation method using Monte Carlo simulations making it possible to estimate surface supersaturation and its transient behavior. Design/methodology/approach: Monte Carlo simulation method is used for investigations of crystal growth from microscopic point of view. It is assumed that the surface supersaturation may be represented by the number of growth units adsorbed on the crystal surface at any given moment. Findings: The presented method allows us to analyze the surface configuration of a growing crystal face and the mechanism of single crystal growth in various assumed growth conditions (supersaturation, temperature). Research limitations/implications: The results of the performed simulations show the influence of changes in bulk supersaturation on the behavior of surface supersaturation, which is very difficult to experimentally measure. In this way, some analytical results calculated previously and concerning transient behavior of surface supersaturation can also be verified. Originality/value: For the first time, Surface Roughening Coefficient (SRC) is defined and the method of its calculation is shown. The SRC coefficient allows us to estimate surface supersaturation determining growth mechanism and, in consequence, determining the quality of grown crystals. The results are useful for control of growth process to obtain good quality single crystals.

5

Experimental analysis of velocity and temperature fields in a system similar to the Czochralski method of single crystal growth

Nowak R., Fornalik E., Groniak J., Szmyd J.

Archives of Thermodynamics

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2008

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Vol. 29, no. 3

83-102

EN

The mixed convection phenomenon plays a very important role in the Czochralski crystal growth due to its essential influence on the heat and mass transport processes. This paper presents the experimental analysis of the natural and mixed convection in the case of a single crystal growth system by the Czochralski method. The influence of such parameters like: temperature difference, rotation of speed of the crystal and the crucible and also aspect ratios were examined. To simulate a configuration of the Czochralski method a glass cylindrical crucible was immersed in a cubic aquarium filled with water. The copper cylinder simulating the crystal (crystal dummy) was attached to the surface of working fluid. Two constant temperature baths were used to control the level of temperature difference between the crucible walls and the crystal dummy. The crucible and the crystal were rotated by the system of engines. Their movement was continuously controlled. Two main methods were applied to investigate the temperature and velocity fields - DPIT and DPIV. The liquid crystal slurry was used as the tracers in both methods. The results are presented in the from of colour temperature maps and vector velocity fields.

6

Wzrost i struktura kryształów roztworów stałych SrAl0,5Ta0,5O3: LaAlO3.

Berkowski M., Fink-Finowicki J., Byszewski P., Diduszko R., Aleksiyko R., Kikalejshvili-Domukhovska R.

Archiwum Nauki o Materiałach

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2003

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T. 24, nr 4

571-582

PL

Wzrost kryształów (SrAl0,5Ta0,5O3)1-x (LaAlO3)x ((SAT)1-x(LA)x) metodami Czochralskiego i topienia strefowego został zbadany w całym zakresie koncentracji poszczególnych składników; struktura otrzymanych kryształów została zbadana metodami dyfrakcji rentgenowskiej. Zaproponowano schematyczny diagram fazowy tych materiałów; roztwory stałe istnieją w zakresie koncentracji 0 mniejsze lub równe x mniejsze lub równe 0,5, w którym kryształy mają strukturę regularną. Metodą Czochralskiego można otrzymać monokryształy w zakresie koncentracji x=0,23/0,41. W otrzymanych kryształach nie stwierdzono występowania przejść fazowych ani zbliźniaczeń niskokątowych. Odpowiedni zakres wartości stałych sieci, wysoka temperatura topnienia tych materiałów wynosząca blisko 1850 stopni Celsjusza wskazuje na ich dobrą termiczną i chemiczną stabilność przy wykorzystaniu jako podłoży dla epitaksji HTSc perowskitów manganowych i GaN.

EN

Crystals of (SrAl0,5Ta0,5O3)1-x (LaAlO3)x ((SAT)1-x(LA)x) were obtained by the Czochralski and floating zone method in whole composition range; structure of these crystals was investigated by X-ray measurements. A schematic phase diagram of this solution is proposed; it was found that solid solutions exist at concentration 0 lto x lto 0.5 and crystals adopt cubic structure. The Czochralski method was successfully used to grow of single crystals with x=0.23/0.41. Structural phase transitions and tendency to formation of twins were no stated. The proper range of lattice parameters and high melting point close to 1850 degrees centigrade indicate their high thermal and chemical stability. Therefore these crystals may be used as substrates for the growth of HTSc, manganites or GaN epitaxial layers.

7

Crystal growth of L(+)-ascorbic acid in a batch crystallizer

Matynia A., Wierzbowska B., Szewczyk E.

Polish Journal of Chemical Technology

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2000

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Vol. 2, nr 1

14-18

EN

The measurements of the crystal growth rate in L(+)-ascorbic acid - water and L(+)-ascorbic acid - alcohol - water systems are presented. The influence of methanol, ethanol and isopropanol on the crystallization system has been studied. Measurements were carried out in the batch crystallizer with inner circulation of a suspension. The effect of the saturation temperature and the cooling rate has been determined. It was found that the rate of crystal growth decreases with the temperature increase, reaching the lowest value (ca 1.3-10-m/s) in the aqueous solution (Teq = 343.5 K) of initial concentration 50 mass % of L(+)-ascorbic acid. At the same temperature, the presence of 20.0 mass % of methanol, ethanol or isopropanol in the solution causes 2 - 3-fold increase of this rate. It may be assumed that for moderate cooling rates the type of alcohol does not influence the crystal growth rate. For higher cooling rates (R,. >16.6710^3 K/s) the differences are ranging from 0.5-10-8 to ca 2-10"8 m/s.

8

Krystalizacja nadpowierzchniowa i zjawiska transportowe towarzyszące korozji szkła krzemianowego sodowo-wapniowego.

Stoch L., Greiner-Wrona E., Ciecińska M., Wacławska I., Trybalska B., Środa M.

Szkło i Ceramika

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1999

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R. 50, nr 3

2-6

9

Symulacja rozrostu ziarn polikryształu zawierającego cząstki drugiej fazy metodą Monte Carlo

Sławuta K., Jeziorski L.

Archiwum Nauki o Materiałach

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1999

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T. 20, nr 1

5-25

PL

Kinetykę rozrostu ziarn w polikrysztale zawierającym cząstki drugiej fazy analizowano numerycznie, stosując metodę symulacji Monte Carlo. Opracowany program pozwala śledzić zmiany wyjściowej struktury modelu oraz dokumentuje obraz i wyliczone parametry stereologiczne w każdym punkcie planu eksperymentu. Do ilościowego opisu hamowania rozrostu ziarn przez cząstki drugiej fazy zastosowano wskaźnik, który uzależniono od względnej powierzchni przekrojów cząstek, ich rozdrobnienia, oraz czasu symulacji. Na podstawie otrzymanych wyników stwierdzono, że w analizowanych przypadkach rozkład wielkości ziarn jest logarytmonormalny, a jego parametry można wyrazić również za pomocą AA, LA(A) i czasu symulacji. Wyniki analizy wyznaczanej funkcji rozkładu porównano z teorią Hillerta.

EN

The kinetics of grain growth in the polycrystal containing second-phase particles was analysed numerically using the Monte Carlo simulation method. The developed program makes it possible to monitor changes in the initial model structure, and documents the image and computed stereological parameters in each point of the experiment plan. For the quantitative description of the grain growth inhibition by second-phase particles, an index was used which was related to the relative area and dispersion of particle cross-sections and the simulation time. On the basis of the results obtained it was found that, in the cases analysed, grain size distribution is logarithmic-normal, and its parameters may also be expressed with the use of: AA, L(A) and the simulation time. The results of the determined distribution function were compared with Hillert's theory.