Thin dielectric films for thermo-dielectric energy conversio

Peltzer, C.

English

NASA Technical Reports Server

June 1966 
QuurtcrI\ h'vliort  (90. 111 1 Cozlering the Period 1 March t o  31 May 1966 
. 
STUDY OF THIN DIELECTRIC FILMS FOR THERMO- 
DIE L E  CTRl C EN E R GY C 0 N VER S IO N 
Prrpured  /vr; 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
AMES RESEARCH CENTER 
MOFFETT FIELD, CALIFORNIA 
By: C. PELTZER 
S R I Project FMU-5671 
Approved: A. E .  GORUM, ASSOCIATE EXECUTIVE DIRECTOR 
P H Y S I C A L  A N D  I N D U S T R I A L  S C I E N C E S  
CONTRACT NAS2-3197 
61 . ~ .{ 
Copy N o .  ..?ti ...... 
https://ntrs.nasa.gov/search.jsp?R=19670007181 2020-03-16T18:43:18+00:00Z
/ 
I f  CONTENTS 
L I S T  OF ILLUSTRATIONS, . . . . . . . . . . . . . . . . . . . . . .  iii 
ABSTRACT.  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  i v  
I INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . .  1 
I1 WORK ACCOMPLISHED - ANALYSIS. . . . . . . . . . . . . . .  2 
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10 
LIST OF ILLUSTRATIONS 
1 
Figure 1 Capacitance versus Temperature at 1 kcps . . . . . . . .  4 
Figure 2 Capacitance versus Temperature at 50 cps . . . . . . . .  5 
Figure 3 Capacitance versus Temperature a t  5 cps . . . . . . . .  6 
Figure 4 Change i n  Capacitance versus Temperature . . . . . . . .  7 
F i g u r e  5 Thermal Cycling ( P o s i t i v e  Voltage) . . . . . . . . . . .  8 
Figure 6 Thermal Cycling (Negative Voltage) . . . . . . . . . . .  9 
i 
iii  
ABSTRACT 
This  repor t  covers t h e  t h i r d  qua r t e r ' s  e f f o r t  on t h e  
study of t h i n  d i e l e c t r i c  f i lms f o r  thermo-dielectr ic  energy 
conversion. The  ob jec t ive  of t h i s  program is  t o  obta in  a 
b e t t e r  understanding of t h e  physical  mechanisms underlying 
t h e  response of c e r t a i n  t h i n  f i l m  dielectrics dur ing  
temperature cyc l ing  and under high e l e c t r i c  f i e l d  condi t ions.  
T h e  temperature dependence of the  d i e l e c t r i c  constant  of 
t h i n  Mylar f i l m  has been inves t iga ted  i n  vacuum as  a func t ion  
of frequency. 
and 30°C gave values  of 
values  a r e  i n  apparent cont rad ic t ion  t o  the  p o s i t i v e  value of 
t h e  order  of +0.001 t o  be expected from the  capaci tance br idge 
measurements. 
Thermal cycl ing runs i n  vacuum between -5O'C 
f3 of t h e  order  of -0.0001; t hese  
i v  
I INTRODUCTION 
This  repor t  covers t h e  t h i r d  qua r t e r  of a research program on t h e  
use of t h i n  d i e l e c t r i c  f i lms  f o r  thermo-dielectr ic  energy conversion. '  
The p r inc ip l e  underlying t h i s  energy conversion scheme may be 
descr ibed as fol lows:  r ad ian t  energy inc ident  on a capac i tor  i s  s tored  
i n  t h e  d i e l e c t r i c  i n  t h e  form of po la r i za t ion  energy and is converted 
i n t o  usable  e l e c t r i c  energy upon discharge of the  capac i tor  i n  a load 
c i r c u i t .  The purpose of t h i s  study i s  t o  inves t iga t e  the behavior of 
c e r t a i n  t h i n  f i l m  capac i tors  under the condi t ions required by t h i s  
energy conversion scheme, i . e . ,  thermal cyc l ing  and high electric 
f i e l d s .  O u r  f i r s t  ob jec t ive  i s  a ca re fu l  examination of t h e  temperature 
dependence of the d i e l e c t r i c  constant 8 of the  d i e l e c t r i c  ma te r i a l ,  i n  
a* obtained ' = e  d t  p a r t i c u l a r  of any divergence between t h e  values  of 
from s t a t i c  measurements and those deduced from thermal cyc l ing  runs.* 
Parameters t o  be considered here, aside f r o m  t h e  temperature,  include 
the appl ied e l e c t r i c  f i e l d ,  cyc l ing  per iod ,  environment, and na ture  of 
t he  e l ec t rodes .  
* C(T)  = capaci tance of t h e  capac i tor  at the temperature T .  
1 
I .  
I1 WORK ACCOMPLISHED - ANALYSIS 
1 
The test  se tup  used f o r  t h e  thermal cyc l ing  experiments c a r r i e d  out  
during t h i s  qua r t e r  i s  b a s i c a l l y  t h e  same as  t h a t  described i n  t h e  f i r s t  
and second q u a r t e r l y  repor t s .  The major d i f f e rence  i s  t h a t  the i n t e r n a l l y  
mounted furnace i n  the  equipment previously used has now been replaced by 
a 650 w a t t  movie f lood  iodine lamp. 
A comprehensive series of capacitance measurements i n  vacuum w a s  
The sample used f o r  these experiments w a s  a 1/2 m i l  Mylar completed. 
f i l m  capac i tor  having evaporated copper e l ec t rodes .  The capacitance 
versus  temperature [ C ( T ) ]  f o r  t h i s  material was measured over t he  range 
of -50°C t o  90°C a t  1 kcps,  50 cps,  and 5 cps ,  with a 1.5-  o r  3-volt 
source (Figs .  1 through 4 ) .  
A s imi l a r  series of runs was made on t h e  same material, using a 
300-volt d.c.  b i a s .  The resul ts  of the  measurements made a t  1 kcps a r e  
i n  agreement with those  previously made and reported i n  which the br idge  
technique w a s  used f o r  measurement. The only apparent e f f e c t  of t he  d .c .  
b i a s  w a s  a s h i f t  of t h e  C ( T )  curves i n  t h e  high d i r ec t ion .  The change 
w a s  on t h e  order  of 10% higher ,  i n  t h i s  case ,  with no not iceable  change 
i n  t h e  s lope  of t h e  curves.  On t h e  o the r  hand, t h e  50 cps and 5 cps 
measurements showed a l a r g e  decrease i n  t h e  s lope  of C(T)  a t  lower 
temperatures--a capaci tance drop of about 3% a t  50 cps ( r e sp .  < 1% at  5 
cps)  from room temperature t o  -50 C ,  as compared w i t h  a drop of > 6% a t  
1 kcps. S t a t i c  measurements using t h e  standard discharge method were 
a l s o  performed over t h e  same temperature range w i t h  charging vol tages  of 
6 and 300 v o l t s .  
N o  appreciable  decrease i n  t he  capaci tance w a s  observed from room temper- 
a ture  down t o  -50 C .  W e  should a l s o  note  t h a t  t h e  s t a t i c  capaci tance was 
higher  than t h e  ones obtained a t  t he  d i f f e r e n t  f requencies .  
0 
A t  temperatures above 70°C, considerable  leakage occurred 
0 
2 
The  open c i r c u i t  test2 i n  vacuum gave t h e  following resul ts :  when 
t h e  capac i tor  was charged ( 6 ,  18, and 300 v o l t s )  f o r  t h e  f i r s t  t i m e  a t  
t h e  low temperature ( - 5 0  t o  - 8 0 ° C ) ,  upon rapid heat ing w e  observed a 
very small drop i n  t h e  vol tage across the  capac i to r ,  corresponding t o  
a pos i t i ve  8 .  On subsequent thermal cyc l ing ,  however, negat ive 8 ' s  
were observed. A s  long as t h e  temperature of t h e  capac i tor  stayed below - 6OoC, t h e  magnitude of t h e  e f f e c t  was small (- 1%); going t o  higher 
temperature r e su l t ed  i n  a l a r g e ,  mainly i r r e v e r s i b l e  drop of t he  vol tage ,  
i n d i c a t i v e  of leakage. 
Using the  same sample we have m a d e  thermal cyc l ing  runs i n  vacuum 
(Figs .  5 and 6 )  from -50'C t o  30°C. The temperature was measured with a 
t h i n  w i r e  chromel-alumel thermocouple. Voltages of 100 t o  500 v o l t s  
were appl ied across  t h e  capac i tor ,  and t h e  cur ren t  flowing i n  and out of 
t h e  capac i to r  during the  thermal cycl ing was obtained from t h e  vol tage 
drop across  a 100 k2 r e s i s t o r  placed i n  s e r i e s  w i t h  the capac i to r .  T h i s  
vo l tage  w a s  picked up through a high impedance (1MSa)  meter,  amplif ied,  
and r eg i s t e red  with t h e  thermocouple e m f  on a Visicorder .  I n  a series 
of runs, w e  obtained records ind ica t ing  a negat ive f3 of t h e  order  of 
-0.0001 t o  -0.0002, i n  c o n t r a s t  t o  an expected f3 from t h e  br idge 
measurements of +0.0012. We should note t h a t  on the  b a s i s  of t h e  5 cps 
capaci tance curve,  or the  s t a t i c  one, w e  would expect a B of l e s s  than 
0.0002 i n  absolute  magnitude. 
For t h i s  reason,  w e  cannot conclude on t h e  b a s i s  of t hese  da t a  alone 
t h a t  there e x i s t s  a c o n f l i c t  between s t a t i c  and thermal cyc l ing  B's. 
Before reaching such a conclusion it w i l l  be necessary t o  obta in  f u r t h e r  
comparative d a t a  on o ther  mater ia ls  besides  Mylar .  W e  are present ly  
engaged i n  obta in ing  such da ta .  Alcar ,  another p l a s t i c  f i l m ,  i s  being 
inves t iga t ed  first. Inorg.auic f i l m s  -:%ll be stl&Fed next, We have set 
up a depos i t ion  apparatus f o r  forming t i t an ium dioxide f i lms  by r eac t ive  
vapor depos i t ion  and w e  a l s o  plan t o  study s i l i c o n  monoxide and aluminum 
oxide f i lms  i n  the  coming qua r t e r ,  The depos i t ion  apparatus f o r  t i t an ium 
dioxide  is  t h e  same as t h e  one reported by Feuersanger.3 
i s  produced by low temperature hydrolysis  of t i t an ium t e t r a c h l o r i d e :  
TiC1, + 2H20 - TiOz + 4HC1 T . Nitrogen i s  being used as  c a r r i e r  gas and 
platinum as  substratum. 
3 
I f  I f  
Titanium dioxide 
w 
4 
I I I I 1 I I I 
5 
6 
I I I 
- 
I 
- 
) - 
1 
0 
I 
- 
0 m 1 I 
0 
In 
0 -  Y r' Y '  * ? c y  - o o o o  o o t o  
I I I I 
3 0  - 33NW113VdW3 NI  39NVH3 
7 
V I S I  CORDER $_ 
1 
300 V Y  
SAMPLE 
100 KR 
0.001 IN. 
( a )  C I R C U I T  D IAGRAM 
0.3 
0.2 
0. I 
0 
rn 
- 
- I  - 
- 
0 -  
m V  - TEMPER AT UR E 
POSIT1 V E  
- 
2 1 1 1 1 1 1 1 1 1 1 1 1 1 1  -1 I- l s e c  
(b) T H E R M A L  C Y C L I N G  D A T A  
T A - 5 6 7 1  - I O  
FIG. 5 THERMAL CYCLING (Positive Voltage) 
8 
1 
I 
. 
- 2  
- I  
0 
m V  
I 
2 
3 
4 
0 
0. I 
0.2 
0.3 
m V  
4 I sec 
T A - S 6 7  1 - 1 1  
FIG. 6 THERMAL CYCLING (Negative Voltage) 
9 
REFERENCES 
1 .  B .  H. Beam, NASA TMX-50, 136; 
J .  D .  Childress  , J .  Appl. Phys. 33, 1793 (1962) .  
I T  2 .  B .  H .  Beam, et a l . ,  Experiments on radiant energy -- 
conversion using t h i n  d i e l e c t r i c  f i lms  ,I' (prepr in t ) .  
3 .  A .  E .  Feuersanger, "Titanium dioxide f i lms  prepared 
by vapor reac t ion ,"  Proc. IEEE, D e c .  1964, p .  1463. 
10 


Study of thin dielectric films for thermo-dielectric energy conversion Quarterly report, 1 Mar. - 31 May 1966

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