GROWTH OF CRYSTALS

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• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 289
• Document Creation Date: December 27, 2016
• Document Release Date: March 7, 2014
• Sequence Number: 4
• Publication Date: October 1, 1959
• Content Type: REPORT

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kV
TIIREISIE1011
GROWTH OF CRYSTALS
(Selected Articles)
By Various Authors
October 1959
282 Pages
STAT
PREPARED BY
LIAISON- OFFICE
TECHNICAL INFORMATION CENTER
MCLTD
WRIGHT-PATTERSON AIR FORCE BASE. OHIO
STAT
?
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Akademii iauk SSSR
Institut Kristallograffii
Doklady
Ua Pervom Soveshohanii
Po Rostu Kristallov
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To the reader:
This translation is in two parts. Part I is a complete
translation of twenty?one selected articles from the book.
Part II is an abstract of six additional articles. A table
of contents precede each part.
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PART I
Complete Translation Of Foreign Pages
-
74-169
128-137
178-189
229-304
311-319
326-340
351-373
-
ii
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Ark
0
Table of Contents
Zan
Effect of Diffusion of Impurities in a Melt on their
Distribution in the Crystal during Directed
Crystallization, by A.I.Landau 1
On the Nucleation of Crystals in Binary Alloys,
13
by Ya.V.Grechniy
A Contribution to. the Question of the Formation and Growth
of Negative Crystals (Pores) Arising from Super-
_ saturated Solutions of Vacancies in the Crystal
Lattice, by Ya.ie.Geguzin 26
Thermal and Diffusional Processes during the Growth of
Crystals, by G.P.Ivantsov 37
The Influence of Modifiers an the Process of Ingot Crystal
lization, by V.Ye.Neymark and A.I.Dtkhin 55
Study of the Processes of Crystallization from a Melt,
by I.N.Fridlyander 70
Artificial Fluorite, by I.V.Stepanov and P.P.Feorilov 88
The Growing of Single Crystals of Lithium Fluoride and
Sodium Fluoride with a High Transparency in the
Ultraviolet and Infrared Regions of the Spectrum,
by M.A.Vasiltyeva 107
Methods of Growing Luminescent Crystals for Scintillation
Counters, by L.M.Belyayev, B.V.Vitovskiy, and
G.F.Dobrzhanskiy 118
Apparatus and Methods of Growing Single Crystals of
Semiconductors, by D.A.Petrov and V.S.Zemzkov 137
First Experiments in Growing Large Mica Crystals, by
K.T.Kapralov, Yu.V.Koritskiy and N.N.Sheitall 152
Synthetic Mica, its Properties and Application, by I.I.Yamzin
and M.S.Leyzerzon 159 .
On the Growing of Single Crystals of Sorbitol Hexaacetate,
by I.S.Rez and L.I.Tsinober 173
The Preparation, Dielectric and Optical Properties of
52--; Single Crystals of Solid Solutions (Ba - Sr)TiO3,
by A.L.Khodakov, M.L.Sholokhovich, Ye.G.Fesenko, and
?Paramarov--. . ? ? ? ? ? ? . ? 000000000000 ?
? -
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,
----A New Technique of Studying -the. Rase- TriniformatiOns-under,_
High Pressures and Temperatures and its Application
to the Study of the Polymorphism of Phosphorous,
_ by V.P.Butuzav and S.S;BOkshi . . . ? ? ? OOOOOOO _198
A New Type of Autoclave for Hydrothermal Synthesis,
by V.P.Butuzov, G.P.Shikhovskoy and S.P.Smirnov ? ? ? ? .? ? 212
?
Technique of Synthesis of Refractory Crystals Insoldble.
in Water, by. I.N.Anikin 217
A Precision Method of Determining the Saturation Temperature
of Transparent Solutions, by A.N.KovalevZkiy 228
Crystallization of Viruses, by V.L.Ryzhkor 234
4A__
4C__
50_2
_J
52-2
56-1
Some Questions of the Kinetics of Crystal Growth,
. bg,V.A.Koptsik 247
Experience of the Work of the Student Practical Course in
the Technology of Artificial Crystal Growing,
by N.L.Pokrovskiy 258
414
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EFFECT OF DIFFUSION OF IMPURITIES IN A MELT ON THEIR DISTRIBUTION IN
THE CRYSTAL DURING DIRECTED CRYSTALLIZATION
by
A.I.Landau
Formulation of the Problem in Partial Derivatives and Methods of Solution
The principle of directed crystallization from the melt is widely used today
for artificially growing large single crystals, and also for the preparation of
ultra-pure substances. There are a number of experimental methods based on this
principle: those of Obreimov and ShUbnikov, Bridgman, Kyropoulos, Stoeber, Stock-
barger (Bib1.1, 2), the method of zone melting (Bib1.3), and others. Since, in the
existing experimental methods of directed crystallization, the rate of advance of
the interface between the liquid and solid phases is slight, the process of crystal-
lization is quasi-stationary, and the liquid melt is always in equilibrium with the
solid phase at their interface, i.e., at the front of arystalli%ation. Here, as is
well known, in accordance with the equilibrium diagram, the liquid melt will become
enriched with the impurity, provided only that the solubility of that impurity in
the solid phase is lover than in the melt (which is what is, for the most part, ob-
served)*. The impurity driven into the melt will be distributed variously in it,
depending on the rate of diffusion,on the convection currents, and on other factors.
In many eases the natural convection in the liquid phase maybe neglected. Thus,
for example, in the Stockbarger method, the crystal grows in the vertical direction
when there is a higher temperature toward the top and the lower temperature toward
the bottom, the malt, enriched with the impurity, has a higher specific gravity than
*In the present work we are considering this ease, but all the results obtained by
us may easily extended. to the ease where the solubility of the impurity in the _
solid-phase is higher than in the melt.
1
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the melt with the lower content of impurity, the interface between the phases is
close to horizontal, the rate of crystal is low, etc. All these factors hinder
natural convection. In this case, the distribution of the impurity in the melt, and
consequently, in the single crystals as well, will depend primarily on its rate of
diffusion in the liquid phase.
In connection with the fact that the diffusion coefficient D of impurities in
liquid melts of salt or metals at temperatures close to the melting point is very
low (D = 10-4 ? 10-5 cm2/sec), the impurity driven into the liquid melt is irregular-
ly distributed in it, accumulating at the boundary of crystallization. To find the
distribution of the impurity along the length of the single crystal it is necessary,
in this case, first to find the distribution of the-inpurity-in tht-liquid-p se at
each given instant of time, i.e., to find the function clic, = clig(x4 t), where cliq
is the concentration of the impurity in the melt*. Then the value of clig(x4
taken at time t1 = x will give us the relation ca = ca(x) - t1)
Here ca is the concentration of the impurity of the solid phase, v the rate of
growth of the crystal, and g is the purification factor, equal to the equilibrium
ration ca/cliq on the boundary of crystallization. The calculation of the function
t) must be carried out by the aid of the diffusion equations
(32c ?
= D
at az=
( 1)
with a boundary condition on the boundary of crystallization of the following form
(Bib1.4, 5):
(1 ?g) vc . D = 01 .
ox x-rt
(2)
*Here x is the length of the single crystal in a fixed system of coordinates, rigid-
ly bound to the container (the origin of coordinates being selected on the front
wall of the container, at the initial point of crystallization). Hereafter we shall
also use a moving system of coordinates Y, where the origin of coordinate will be
selected on the moving boundary of crystallization. In both cases the coordinates
will be measured in the direction toward the liquid phase. The statements here made
about the moving and fixed coordinate systems relate to the figures in this paper.
2
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:??."
r-'
- - - - - - - - ---------- _ _
The second boundary condition, on the opposite side of the column of the melt, and
the initial condition, have the following forms:
and
(3)
(4)
where L is the length of the container (i.e., the original length of the column of
melt). Thus, in this case, one of the boundary conditions is assigned on the non-.
stationary (moving) boundary. This kind of problems, if they are solved in the
general form, are among the most difficult in mathematical physics. It is most con-
venient of all to perform the numerical solution of the system (1) - (4) by the aid
of the method of finite differences. Let us pass to the moving coordinates Y, the
origin of which has been chosen on the boundary of crystallization. In this system
of coordinates, eq.(1) will have the following form:
D
a2C ? & ?
v
as ay2 ay ?
(5)
The derivatives aclig(at, aclig(ay and a2cliq/3y2, written in finite differences,
will be, respectively, of the following form:
and
a
ciark+1 ? citig k) ; Mr*
2h
?i k_ 2ci.i k cfrl, k
tr
h* _
_ _ ? _ _ _ _ _ _ _ _ _ _ _
Here t is the interval in time; h is the interval in length; k is the number of
the cell along the t axis; i is the number of the cell along the y axis. Let us
choose the following relation. between the time and space interval:
(6)
With such a choice of the dependence between t and h, the error of the calculation
is-of the same order of magnitude as h4 (Bib1.6, 7), while eq.(5), written in
SI-AT
3
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1.
1
differences, takes the following forlii-
1, k+j, (1 Ito \ k 1 IW \ ;44, k
cjjq= 72?
clif )Ciki
The boundary conditions (2) and (3) and the initial-cOndition (4)-iiiii.ihen read re-
spectively as follows:
o.k 2h(1?g)vk k
= -r
(L?iolk-40111, k(L?v1k)ik, k
C mc Gun
1.
_
for all values of i
Results of Solution and Fundamental Equations
Calculations performed by the method of finite differences by the aid of
eqs.(7) - (10) yield the distribution of the
c4111
Ji impurity in the liquid phase which is shown
40
by us in Fig.l.
!
Ag c
it- These calculations also show that in the
2 f7 4 1 yam initial period of time the concentration
Fig.1 - Distribution of Impurity barrier of the impurity in the melt rapidly
in a Melt Close to the Boundary
of Crystallization, Calculated increases. Then follows its gradual stabili-
for D = 10-4 cm2/sec, v =
= 3.6 mm/hr, Cjq = 5% and g = zation, and the distribution of the impurity
0.1 at time t = 53 hr after in the liquid phase approaches a certain
Beginning of the Growth of the
Crystal; the Origin of Coordi-
asymptotic curve resembling that shown in
nates is Taken on the Boundary
of Crystallization; X is the
Fig.l. The equation describing this curve is
Characteristic Thickness of the
Concentration Barrier
easily found from the following considera-
tions. First of all let us assume that the concentration barrier has already become
completely stabilized and that the distribution of the impurity in the melt is de-
scribed by eq.(5) at aculiat ? 0, i.e., by the equation
D 81/414 v -22k o
ays ? py ?
?
4
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We note further that, as will be seen from Fig.1, the characteristic thickness X of
the concentration barrier of the mixture close to the boundary of crystallization is
not great and is smaller by one order than the dimensions of the container (L 16 ?
? 20 cm or more). For this reason we may consider the front of crystallization on
the opposite side of the container as being at infinity. The boundary conditions in
this case takes the following form (the origin of coordinates being chosen at the
boundary of crystallization):
(1--.61n411-D?A. ?. 01
(12)
and
cili0)?*41if at y.--).00.
Solving the system (11) ? (13) by the usual methods, we get:
0 [(1?g)
Cb(y) = Ciii g
q
(13)
(14)
It follows from the asymptotic formula (14) that, in the stabilized concentration
bo
barrier, the concentration, clig, of the impurity at the boundary of crystallization,
bo
is connected with the quantity c5liq by the following relation: clic" = qici/g*. In
bo
this case, the impurity will enter the crystal in the concentration ca = gcliq =
o
, i.e., in a concentration equal to the initial concentration of the impurity
in the melt (cf.Bib1.5). The characteristic thickness X of the concentration barri?
er may also be evaluated from eq.(14):
(15)
At D = 10-4 cal2/sec and v = 3.6 mm/hr, we shall have X= 1 cm (cf.Fig.1); at the
*Obviously, however c5liti gclui g (Fig.la), the
distribution of the concentrations of vacancies will be such that there will be a
_
flow of vacancies from the surface of the pore, which corresponds tb the process
of "sintering" the pore, or to a decrease in its size. When Acr
z ...;......
1
.
gions, in which the contaminations are
concentrated, are likewise formed in them.;
These .regions usually occupy a volume in
the crystal in the form of an inverted
cone, with the vertex at the bottom
(Fig.2). Most of the crystal, however,
grows without color, but with a faint
opalescence, and of moderate transparency
in the shortwave part of the spectrum.
It was found during the work that the
contaminated parts of vacuum-grown crys-
2.74 187 a
tals do not contain silicon nor aluminum,
as is the case in crystals grown in the
ordinary atmosphere. This is explained by
the ease of distillation of their fluorine
compounds in the vacuum. The principal
-
cOntaminant of such parts is Ii20, a com-
pound which is nonisomorphic with LiF. In crystals grown in the atmosphere; how-
ever, Li20 cannot be detected. They do, however, contain a certain quantity of
UCH, which does enter isanorphously into the LIF crystal lattice. Thus, on heating
.kor
Fig.4 - Transmission (T) of Lithium
Fluoride Crystals
The crystals were grown: 1 - In
the air; and 2 - In vacuo
and melting lithium fluoride in vacuo, it is freed from the principal isomorphous
- impurity (UCH) and becomes genuinely pure.
_
The crystals so grown were broken up into large lumps, from which the clowty
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- parts were carefully removed. The transparent parts, however, were then utilized as
raw material for regrowing,
The regrown crystals already differ markedly in their optical indices fran the
crystals grown in vacuo after the first crystallization, and still more from crystals
grown from the same raw materials under ordinary atmospheric conditions (by the
Kyropoulos or Stockbarger method).
Figure 3 gives the curves of spectral transmission of lithium fluoride crystals
twice grown in vacuo, and of sodium fluoride, also grown in vacuo.
For a final conclusion as to the quality of lithium fluoride crystals grown in
vacuo, we give in Fig.3 a transmission curve of a good specimen of optical fluorite.
It will be seen that lithium fluoride transmits further in the shortwave ultraviolet
region than the best specimens of fluorite, namely down to 105 n44 while the best
fluorite specimens are transparent only down to 125 - 130 mg. Figure 4. shows the
transmission of lithium fluoride crystals in the infrared regions, grown in the at-
mosphere and in vacuo. The vacuum-grown crystals have a higher total transmission
(almost 10% higher); and also have no absorption bands of water in the 2.7 ? region.
Another practically important result of this work is the possibility, demon-
strated by us, of using certain base metals as a material for crucibles employed for
growing lithium fluoride and sodium fluoride crystals. The following base metals
with a high melting point were tried: Fe, Ni, No, W, Tl. Experience showed that
- all these materials are entirely resistant to the action of melts of lithium and Na
--fluoride, and also of calcium fluoride (fluorite), provided water vapor and oxygen
-
are absent from the surrounding medium. The single crystals of lithium fluoride and
45?
,_--sodiun fluoride that are vacuum-grown in crucibles of these materials have no spe-
-!-J--
--cific tinge due to the presence of these metals. More precise spectrophotometric
z---
,?:--studies likewise failed to reveal their presence in the crystals grown.
*A .7
It should be noted that the upper limit of the temperatures at which the utili-
zrzation of one base metal or another is possible, lies below its melting point, and is
-1
STATS
3.15.
1
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determined by the beginning of its intense vaporization in vacuo.
Another remarkable property of the metals so tested was the unwettability of
their surfaces by melts of fluorides (except for tantalum). The crystals grown do
not intergrow with the walls of the crucibles, and are removed from them with perfect
freedom. This property advantageously distinguishes these metals even from platinum,
so widely used, which is very difficult to separate from the crystal: the crucible
Fig.5 - Lithium Fluoride Crystals
must be broken and the crystal removed from it in small parts. By comparison with
metal crucibles (iron, nickel, and molybdenum), crucibles made of the pure grades of
artificial graphite have great advantages. Their shape does not change under ther-
mal and mechanical influences taking place during the growth of the crystals. Many
tens of lithium fluoride or sodium fluoride crystals can be grown in a single
graphite crucible. The manufacture of graphite crucibles is considerably simpler
than that of metal crucibles, especially those of molybdenum.
The possibility of replacing platinum by base metals opens up wide possibili-
ties of industrial manufacture of lithium fluoride crystals of large sizes and high
quality, using vacuum technology.
Thus, we consider the possibility of growing lithium fluoride crystals with the
116
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1.?
widest transmission in the Schumann region of the spectrum, and without .selective
absorption bands in the infrared region, to have been established. For growing
high-grade lithium fluoride crystals (Fig.5), starting material of average quality
may be used.
The possibility of avoiding the use of the noble metals considerably simplifies
the problem of industrial preparation of these crystals.
BIBLIOGRAPHY
--1. Stockbarger,D. - Preparation of Large Single Crystals of Lithium Fluoride.
Rev.Sei.Inst., Vol.? (1936), PP.133 - 136
- -- 2. Cramers, - Synthetic Optical Crystals. Ind.Eng.Chem. (Industrial Ed.)
Vol.32, No.11 (1940), PP.1478 - 1483
- 3. Stepanov,I.V., and Feofilov,P.P. - Artificial Fluorite. This Symposium,
?
46 ?
4 C. --
52-
5.!
Z 4
;
?
P.229
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METHODS OF GROWING LUMINESCENT CRYSTALS FOR SCINTILLATION COUNTERS -
L.M.Belyayev, B.V.Vitovskiy, and G.F.Dobrzhanskiy
The use of crystals of a number of luminescent substances in physical instru- ?
ment building began in 1947 - 1948. The widely known method of registration of
nuclear radiation by the aid of scintillAtions (Bib1.1) has been considerably
proved in recent years. The visual method of counting the scintillations has been
replaced by photoelectric registration by the aid of what are called electron multi-
pliers (Bib1.2). A zinc sulfide screen, and a considerable number of-crystalline,
plastic and liquid phosphors are being used. The combination of a photoelectronic
-multiplier, a crystalline, plastic or liquid scintillator, and a special radio-
circuit counting device has received the name of scintillation counter (Bib1.3).
Such a scintillation counter is finding wider and wider application for the registra-
tion of nuclear radiation and in studies of the radiations emitted during operation
of various particle accelerators. The scintillator (crystalline, plastic or liquid
phosphor) plays an important role in such instruments, for it serves as a peculiar
transducer of the invisible nuclear radiation into visible radiation. This trans-
formation takes place at the instant of interaction of the radiation with matter.
The character of the interaction of various forms of radiation with matter varies.
Taking these differences into account, the requirements for scintillators are now
formulated, and a rather broad class of substances used for these purposes has been
found. We shall discuss only the crystalline scintillators.
For _crystalline scintillators to meet the demands made on them, the crystals '
--must possess:
-
1) Rather high density, and the presence of chemical elements and isotopes
-which are most reactive for the given form of radiation;
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2) High physical effectiveness (the proportion of the absorbed energy converting
- into-light must be high) and low transparency for its own radiation; the region of
its awn radiation must, to the maximum degree, correspond to the region of spectral
- sensitivity of the photocathode of the electron multiplier;
3) Short quenching time, i.e., law inertness;
4) Good mechanical properties, good heat and moisture resistance, so that they
can be used under various conditions.
We present a list of the crystals used in practice as the most effective scin-
1
44 '
_tillators. These substances are conveniently divided into two groups, organic and
Table 1
Name
-
Melting Point
oc
-facr%
,-1 0
mu
g ici
Maximum of
Radiation .
Spectrum, A
Characteristic
Absorption
Maximum,
Luminescence
Decay, sec
Naphthalene C10H8
80
1,15
3450
6.10.4
Anthracene CION
216
1,28
4400
4050
3.10-4
Phenanthrene C 1010
101
1,03
4100
8k10-4
4300
Chrysene. Cl8H12
254
4190
4.10-4
3520
Dibenzyl Ci4Hik
52
1,0
3950
1,5.10-4
Stilbene C1012
124
1,16
4200
8-104
.
408D
To lane C14510
62,5
1,18
3900
6.10.4 .
Terphenyl C1014
213
1,23
4000
1,2.10-4
Quaterphenyl C2018
318
4200
8-10-4
:
?

_inorganic. The two groups differ not only in chemical composition, but also in the
48?
_mechanism of the luminescent processes that take place in them (Bib1.4). Table 1 is
--i list of the most effective organic substances, and their physical and chemical
52-1.
--Characteristics.
Table 2 lists the inorganic substances, and gives their physical and chemical
56-1 -
,
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? characteristics.
. -
be seen from Tables 1 and 2 that the use of various methods is required
for growing crystals of these substances. It must be added that the specific nature
Table 2
Substanceo
Melting Point
?C
,
4.30 .?
?ri 0
0) 0
= \
rt) 6
Refractive
Index
44 64
o .
g
19
P 10 4131
1 in 0
.A31.
43 ?
?ri -
si o*
V ?rt .4
;all
. 0
10
ESQ
-
luminescence ?

Decay, ,!Ie
? ? -, -...
?
_
.
LiEtr(Tl)
547
3,464
1,784
'
LA1(T1)
446
4,06
1,955
4500
>10-?
1(1(T1)
682
3,13
1,677
4100
2870
2360
>10-41
Ma(T1)
651
3,67
1,770
4100
2930
240-7+340-7
1,48 .
2340
2,5.10-7
CSF
684
3,59
1,578
4000
5.10-0
CsBr(11)
636
4,44
1,582
1,608
?
ulturielst
?
CSI(TJ)
621
4,51
1,787
2410
2190
s
5.10-7-4-11,1.10-4
2990
4350
Rid(Ti)
642
3,55
1,648
4800
CaW04
1535
6,10
1,920
4300