The solubility measurement system and the laser scattering microscope system were designed, built, and utilized for the study of crystal growth solutions and crystal characterization measurements. Solubility measurements and crystal defect maps were made with this equipment for a number of new materials. In some cases, where there have been published solubility data (i.e., TGS), more accurate measurements were made and discrepancies in the published data were resolved. The design of these instruments is presented along with a description of their use and some typical data generated using them

Kroes, Roger L.

Reiss, Donald A.

English

NASA Technical Reports Server

6 5 
NASA 
Technical 
1 Memorandum 
. 
NASA TM- 100371 
. 
DEVELOPMENT OF NEW TECHNIQUES FOR THE 
CHARACTERIZATION OF CRYSTALS AND T H E I R  
GROWTH SOLUTIONS 
CENTER D I RECTOR ' s D I SCRET I ONARY FUND F I NAL REPORT 
By Roger L. Kroes and Donald A. R e i s s  
Space Sc ience  Labora tory  
Sc ience  and Engineer ing  D i r e c t o r a t e  
June  1989  
[NASA-TM-100371) D E V B L U P N E N T  OF NEW N89-26741 
TECBNXUUES FOE THE CHARACTERIZATION O f  
C3Y STALS A N D  T H E i R  GROWTH SOLUTlONS:  CENTER 
UiRECTOa'S DISCHETIUNARY F U N D  E i n d l  Report Urrclas 
(NASA, Marshall Space Fliqht Center) 2 1  p G3/76 0219845 
Nationa! Aeronautics and 
Space Administration 
George C. Marshall Space Flight Center 
MSFC - Form 3190 (Rev. May 1983)  
https://ntrs.nasa.gov/search.jsp?R=19890017370 2020-03-20T02:17:40+00:00Z
I 
c 
NASA TM- 100371 I 
4. TITLE AND SUBTITLE 
TECHNICAL REPORT STANDARD TITLE P A G E  
1. REPORP NO. 12. COVERNkENT ACCESSION NO. I S .  RECIPIENT'S CATALOG NO. 
5. REPORT DATE 
Roger L. Kroes and Do- 
9. PERFORMING ORGANIZATION NAME AND ADDRESS 
George C. hlarshall Space Flight Center 
Marshall Space Flight Center, A L  35812 
12. SPONSORING AGENCY NAME AND ADDRESS 
Development of New Techniques for the Characterization of June 1989 
Crystals and Their Growth Solutions--Center Director's 6. PERFORMWG ORGANIZATION COO€ 
10. WORK UNIT NO. 
11 .  CONTRACT OR GRANT NO. 
13. TYPE OF REPORT (L PERIOD COVERE0 
Discretionary Fund Final Report I ES76 
7. AUTHOR(S) I 8. PERFORMING ORGAN1 ZATION REPOR f 1 
19.  SECURITY CLASSIF. (d thL n~-> 21. NO. OF 2AGES 22. =RICE 20. SECURITY CLASSIF. (of PI*) 
National Aeronautics and Space Administration 
Washington, DC 20546 
Technical Memorandum 
14. SPONSORlNG AGENCY CODE 
I 
15. SUPPLEMENTARY NOTES 
Prepared by Space Science Laboratory, Science and Engineering Directorate 
!6 .  ABSTRACt  
The solubility measurement system and the laser scattering microscope system were designed, 
built, and utilized for the study of crystal growth solutions and crystal characterization 
measurements. With these instruments we have been able to make solubility measurements and 
crystal defect maps for a number of new materials. In some cases, where there have been 
published solubility data (Le., TGS), we have been able to make more accurate measurements and 
resolve discrepancies in the published data. The design of these instruments is presented along 
with a description of their use and some typical data generated using them. 
17. KEY WORDS 18. DlSTRlEUTlON STATEMENT 
Solution Crystal Growth, Solubility, Crystal 
Defects, Crystal Characterizatiw, Light 
Scattering Microscope 
Unclassified-Unlimi ted 
TABLE OF CONTENTS 
I .  
I .  
Page 
Introduction 1 
Solubility Deter mination ......................................... 1 
Laser Scattering Microscope ...................................... 
.................................................. 
4 
Conclusion 14 
References .................................................. 16  
................................................... 
PRECEDING PAGE BLANK NOT FILMED 
iii 
LIST OF ILLUSTRATIONS 
Figure 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
Title 
Solubility measurement system ............................ 
Shadowgraph of growing TGS crystal 
Solubility of TGS in water 
Solubility of LAP in water 
Solubility of urea in water 
Solubility of urea in ethanol 
Solubility of urea in isopropanol 
Solubility of A1 alum in water 
Schematic of laser scattering microscope 
Light scattered from TGS crystal 
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iv 
TECHNICAL MEMORANDUM 
DEVELOPMENT OF NEW TECHNIQUES FOR THE CHARACTERIZATION 
OF CRYSTALS AND THEIR GROWTH SOLUTIONS 
Center Director's Discretionary Fund Final Report 
INTRODUCTION 
In order to carry out an exacting program in solution crystal 
growth along with analysis of the growth process applying 
mathematical models, it is necessary to be able to accurately 
determine the solubility curves for the materials of 
interest. It is also important to be able to characterize 
the degree of perfection of the crystals produced in order to 
properly optimize the growth parameters. The purpose of this 
project is to expand the in-house solution crystal growth and 
characterization capability in the Space Science Laboratory 
at MSFC. An investigation of the growth of triglycine 
sulfate (TGS) has been conducted at MSFC over the past 10 
years. 
Experiment System (FES) on Spacelab 3. Two ferroelectric 
crystals of TGS were successfully grown in the FES on this 
flight. With the conclusion of the post-flight analysis, the 
solution crystal growth and characterization program at MSFC 
is being extended by the addition of new growth and 
characterization systems and the investigation of new 
materials, with emphasis on electro-optical materials. 
This work culminated in the flight of the Fluid 
This paper describes two new and unique systems which were 
designed and developed under this program for the 
characterization of crystal growth solutions and for the 
mapping of defects in transparent solution grown crystals. 
These systems are the solubility measurement system and the 
laser scattering microscope. Both systems have been brought 
into operation in our laboratory and are described along with 
some of the experimental results they have produced. 
SOLUBILITY DETERMINATION 
One of the most fundamental aspects of solution crystal 
growth is the determination of the solubility curve. It is a 
plot of the equilibrium concentrations of the growth solution 
as a function of temperature. 
at any given temperature is the concentration at which no net 
growth or dissolution occurs. 
The equilibrium concentration 
A knowledge of the solubility 
curve is essential if the researcher is to control the growth 
process with precision. 
The solubility curve cannot normally be calculated from 
fundamental solution parameters and must be obtained 
experimentally. 
temperature dependence curve. 
express this temperature dependence of concentration are: 
The data points are often fitted to a 
Two equations commonly used to 
c = A+BT+CT~+. . . (1) 
where c = concentration expressed in mass of solute per 
given mass of solvent, and T is temperature in degrees 
centigrade. A,B,C are constants and can be found in the 
literature for many common substances. 
log x = a/T + b (2) 
where x is the mole fraction of non-solvated solute in 
solution, T is the temperature in degree K, a and b are 
constants. 
The latter equation has the advantage that a plot of log x 
versus 1/T gives a straight line plot. 
The solubility measurement apparatus is shown in Figure 1. 
It consists of a temperature-controlled water bath, a test 
cell containing a small crystal immersed in its growth 
solution, and an optical system consisting of a laser with a 
beam expander, collimating lens, and an ima e screen. The 
bath temperature can be controlled to 0.01 'C and has an 
operating range of 0 to 100 OC. 
capacity of approximately 150 ml. 
thin-walled glass for efficient heat transfer giving quicker 
response to temperature adjustments. 
feed-through for a separate temperature sensor so that any 
differences in temperature between its interior and that of 
the water bath can be recorded. 
The test cell has a volume 
It has been built with 
It also contains a 
Initially the concentration of the solution to be tested is 
made to an arbitrary or estimated value. The cell is filled 
with the solution, and a small crystal of the material 
mounted on the end of a glass rod is inserted into the cell. 
A thermal sensor is also inserted and sealed into the test 
cell. The test cell is then placed in the preheated water 
bath and the optical system turned on. With the crystal 
suspended in the solution and an arbitrary temperature set, 
the crystal will either be in a growth or dissolution mode. 
2 
Figure 1. Solubility measurement system. 
3 
This will produce a concentration depletion or enhancement 
region surrounding the crystal. 
this depletion region, which is less dense than the 
surrounding solution, will rise to the surface as a growth 
plume and be clearly visible in the shadowgraph image 
projected on the screen by the collimated laser beam. 
Similarly if the crystal is dissolving, a dissolution plume 
falling from the crystal will clearly be visible in the 
shadowgraph image on the screen. 
bath can be adjusted to slowly bring the crystal and its 
solution into equilibrium, and this will be confirmed by the 
absence of a growth or dissolution plume in the shadowgraph 
image. 
This is a very sensitive process and gives an equilibrium 
temperature with a very high degree of accuracy. 
concentration of the solution can be changed and the process 
repeated in order to get the equilibrium temperatures over an 
extended range of concentrations. 
temperatures are then plotted versus the corresponding 
solution concentrations and the solubility curve generated. 
Figure 2 shows the shadowgraph image of a growing crystal 
with its associated growth plume rising toward the surface. 
This apparatus has been used by the authors to generate 
solubility curves for a number of materials of interest and 
also to remeasure some previously known data in order to get 
increased accuracy. Figures 3 through 8 show the measured 
solubility curves for a number of different materials of 
interest. 
method has enabled the authors to control the growth process 
of crystals with greater precision, producing consistently 
better results. 
If the crystal is growing, 
Then the temperature of the 
The 
The equilibrium 
The high degree of accuracy obtained by this 
LASER SCATTERING MICROSCOPE 
In any crystal growth study it is imperative to be able to 
properly evaluate the quality of the crystals produced and to 
use this comparison to evaluate different growth techniques 
or different values for growth parameters in order to 
optimize a system or process. 
for all crystals. Electrical, structural, chemical, or 
optical properties are all measured differently. 
these techniques require cutting, shaping, modifying, or 
destroying the crystal to get the desired measurement. 
In solution crystal growth many crystals of interest are 
optically transparent, and their most prevalent growth 
No single technique is good 
Some of 
. 
4 
. 
ORIGINAL PAGE IS 
OF POOR QUALIW 
Figure 2. Shadowgraph of growing TGS crystal. 
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defects are small voids or inclusions. In such crystals 
these defects act as light scattering centers. The laser 
scattering microscope was designed and built to detect, 
measure, and map in three dimensions these light scattering 
centers. A particular advantage to using this instrument is 
the fact that it is a non-destructive test procedure which 
leaves the crystal available for other test procedures and 
for fabrication for device applications. It is a 
particularly useful method for mapping regions in the crystal 
of exceptionally high quality which can be cut out of an 
otherwise mediocre quality crystal and used in applications 
requiring a high degree of uniformity and perfection. 
fact that this instrument is only applicable to transparent 
materials is not as limiting as it might first appear since 
optically transparent, solution-grown crystals form a large 
class of the technically interesting crystals. 
Figure 9 is a schematic of the laser scattering microscope. 
It consists of a laser optical system, sample stage, 
microscope, electronic detection and control system, and 
computer system for data acquisition and analysis. 
crystal is mounted in the sample chamber which is then filled 
with a silicone fluid made to match the index of refraction 
of the crystal. 
The presence of this index matching fluid greatly reduces 
light scattering from the crystal surface at the points where 
the laser beam enters and exits. In this way we are able to 
detect growth defects very close to the surface without their 
presence being masked by scattered light from the surface. 
The light incident on the crystal comes from a 10 mW helium- 
neon laser which after passing through a chopper is focused 
down to a very narrow beam before entering the crystal. 
Next, crystal and laser beam are aligned with respect to the 
microscope. Light scattered from defects in the crystal is 
focused by the microscope on a photo detector whose signal is 
fed to the lock-in amplifier which is synchronized with the 
chopper wheel to reduce background noise. 
lock-in amplifier is fed to the data acquisition system which 
consists of an IBM model 30 PC computer and specially 
designed software. 
Three-dimensional maps of the defect structure in the crystal 
are made by stacking a series of two-dimension maps gotten by 
scanning a given plane in the crystal using the programmed 
X-Y moveable sample stage. 
preselected steps of about 20 microns over an adjustable 
range along the X and Y axis of the crystal. 
The 
A sample 
The output of the 
This scanning is done in 
The scanning of 
12 
Pinhole y Lod<-in I 
Amplifier 
0 Conver. 
Microcomputer 
B Storage 
He-Ne 
Laser 
Translation Stages 
Figure 9. Schematic of laser scattering microscope. 
13 
the crystal and the measurement of scattered light intensity 
at each step is coordinated by the data acquisition system 
and directed by a software program specially written for this 
instrument. A graph of the data can be displayed either on 
the computer screen or a hard copy made on the HP plotter. 
Figure 10 shows a plot of the positions and intensities of 
scattered light from a fixed plane in a TGS crystal. The 
intensity of the scattered light is proportional to the 
defect size. In this way the laser scattering microscope 
produces a highly accurate mapping of relative sizes and 
positions of defects in solution-grown crystals. 
CONCLUSION 
The solubility measurement system and the laser scattering 
microscope have significantly increased the capabilities of 
our solution crystal growth effort. The increased accuracy 
of solubility data enables us to control crystal growth 
processes to a higher degree of precision and also to better 
compare experimental growth rate date with theory by having 
more accurate data. The laser scattering microscope has 
added to our crystal characterization capability with its 
unique defect mapping ability. Since this is a 
nondestructive procedure it leaves the crystal free for other 
subsequent applications. 
our use of this instrument to include a number of new 
materials of interest. 
We are in the process of extending 
14 
I .  
15 
REFERENCES 
1. Kroes, R.L. and Reiss, D.A., Properties of TGS Aqueous 
Solution for Crystal Growth. J. Crvstal Growth, 69, 414- 
420, 1984. 
2. Reiss, D.A., Kroes, R.L., and Anderson E.E., Growth 
Kinetics of the (001) Face of TGS Below the Ferroelectric 
Transition Temperature. J. Crvstal Growth, 84(1), 7-10, 
1987. 
3. Kroes, R.L. and Reiss, D.A., The Pyroelectric Properties 
of TGS for Application in Infrared Detection. NASA TMX- 
82394, January 1981. 
4. Kroes, R.L., Reiss, D.A. ,  Silberman, E. and Morgan, S., 
Diffusion of Triglycine Sulfate in Aqueous Solution. 
Phvs. Chem., 89(9), 1657-1658, 1985. 
5. J . W .  Mullin, (Irvstallisation , CRC Press, Cleveland, Ohio, 
Chapter 2, 1972. 
J. 
t 
16 
APPROVAL 
DEVELOPMENT OF NEW TECHNIQUE FOR THE CHARACTERIZATION OF 
CRYSTALS AND THEIR GROWTH SOLUTIONS-CENTER DIRECTOR'S 
DLSCRETIONARY FUND FINAL REPORT 
By Roger L. Kroes and Donald A. Reiss  
The  information in th i s  repor t  has  been reviewed for technica l  content .  Review of 
any information concerning Depar tment  of Defense or nuclear energy ac t iv i t ies  or pro- 
grams has Seen made  by t h e  MSFC Securi ty  Classification Officer. This report ,  in i t s  
ent i re ty ,  has  been de termined  to be unclassified. 
, 
J 
E. TANDBERG-HANSSEN 
Director  
Space Science Laboratory 
17 


Development of new techniques for the characterization of crystals and their growth solutions: Center director's discretionary fund

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