Article
Reference
Spontaneous polarization, dielectric constant, D.C. resistivity, and specific heat of orthorhombic boracite Fe
3B
7O
13I
SCHMID, Hans, et al.
Abstract
Iodo Fe boracite properties are: spontaneous polarization (25°C) 3.9 × 10-2 cm-2, dielec.
const., ε33, (25°C) 11, d.c. resistivity (71°C) 1.1 × 108 Ω m (mm2) and 3 × 106 Ω m (̅43m), vol. sp. heat (25°C) 3.5 × 106 J/m3/K, latent heat 3.1 × 103 J/mol, and transition entropy 8.9 J/mol/K.
SCHMID, Hans, et al . Spontaneous polarization, dielectric constant, D.C. resistivity, and specific heat of orthorhombic boracite Fe
3B
7O
13I. Ferroelectrics , 1976, vol. 13, no. 1, p.
351-352
DOI : 10.1080/00150197608236608
Available at:
http://archive-ouverte.unige.ch/unige:33563
Disclaimer: layout of this document may differ from the published version.
1 / 1
Ferroelectrics
1976, Vol. 13, pp. 351-352
© Gordon and Breach Science Publishers Ltd., 1976 Printed in Great Britain
S P O N T A N E O U S P O L A R I Z A T I O N , D I E L E C T R I C C O N S T A N T , D C . R E S I S T I V I T Y , A N D S P E C I F I C H E A T O F O R T H O R H O M B I C
B O R A C I T E Fe3B70i3l
H. SCHMID, P. CHANt, L . A. PETERMANN,t F . TEUFEL,§ and M. MANDLY Battelle Geneva Research Center, 1227 Carouge, Switzerland
(Received September 22, 1975)
Several properties of ferroelectric orthorhombic Fe-1 boracite have been measured; some individual values are:
spontaneous polarization P. (25°C) = 3.9 ± 0 . 1 x 10"^ cm"^, dielectric constant 633 (25°C) = 11, D.C. resistivity P (71°C, wm2) = 1.1 X 1 0 ^ n m , p ( 7 1 ° C , 4 3 m ) = 3 x 10* Hm, volume specific heat C„ (25°C) = 3.5 ± 0.3 x 10*
Jm"3 Kl a t e n t heat = 3.1 ± 0.3 x 10^ Jmole"^, transition enthalpy A5 = 8.9 ± 0.5 Jmole * K ' .
The spontaneous polarization of F c s B v O i s l in its mml phase has been measured at 25°C under simul- taneous visual control. The Sawyer-Tower method' at 50 Hz and the Camlibel pulse method^ both gave a value ofP, = 3.9 ± 0.1 x 10^ Cm'^ . At the Curie point Tc (71 -12°C) integration of the charge during the first order polarization breakdown yielded = 3.7 ± 0 . 1 X 10"^ C m-2.
The temperature dependence of the dielectric con- stant was measured parallel to in the poled mm2 phase (633) and in the 43m phase (Figure 1) using a micromanipulator and evaporated guard ring electrodes.
20 -
o o o 15 a:
o t - UJ
y 10
Q
50 100 TEMPERATURE ['C]
F'lGURE 1 Electric resistivity of Fe3B70i3l vs. reciprocal temperature.
t New address: Orbisphere Laboratories, 1227 Geneva, Switzerland.
X New address: ASUAG, 2503 Bienne, Switzerland.
§ New address: IBM Laboratories, Boblingen, Germany.
Following Sailer's^ fit of e of Mg-Cl boracite to Curie laws of the form
and
e^m- e / + ^ - ( e / , € / ; C ^ C ^ ; r / a n d r /
being the para- and ferroelectric temperature indepen- dent part of e, Curie constants and Curie-Weiss tem- peratures, resp.), the Curie-Weiss law of Fe3B7 0 i 3 l becomes obvious (Figure 2). This behaviour would be consistent with the requirements of the phenom- enological theory of Levanyuk and Sannikov,''
0,50 -
o>o
0,30- 0,20 -
0,10
' c 1 1
300 350
T E M P E R A T U R E [ ' K ]
400
F I G U R E 2 Dielectric constant (1 MHz, 15 mV) of Fe3B70i3l I's. temperature.
351
352 H. SCHMID et al.
The temperature dependence of the D.C. resistivity was measured at 4.5 Volts in the mnil phase and in the 43m phase using a guard ring method. Respective activation energies of Emm2 ~ 1.17 eV and £ ' 4 3 ^ - 0.52 eV were observed. At Tc the resistivity jumps abruptly from Pmmi = 1.1 x 10* 12m to p'izm = 3 X 10^ fim (Figure 3).
10"
-.10'°
(/) ui a:
O UJ
in
1.17eV
73*C
7rc
-0.52eV
J I I I L I I I I
2,5 3.0 3,5 RECIPROCAL TEMPERATURE [lO^K"!
F I G U R E 3 Curie-Weiss law of Fe3B7 0 i 3 L
the transition to occur within 0.2°C. The data points therefore reflect the true behaviour of the specific heat anomaly. The broad peak of Cp observed between - 6 0 ° and - 8 0 ° C (Figure 4) corresponds to the tran- sitions 3m±^m ^ mml,^ but resolution was poor owing to sluggishness of these transformations.
. ^ 0 . 5 0 J c
'01
•3 0,40 o a.
< 0,30 UJ I CJ
t 0,20 o
LU a . (/)
0.10
Weight of crystal: 47,4 mg Heating speed:4Vmin
-50 0 50
T E M P E R A T U R E ['C]
100 150
F I G U R F : 4 Specific heat of F e 3 B 7 0 i 3 l vs. temperature
( 1 9 0 ^ 2 5 K ) .
ACKNOWLEDGEMENTS
The authors gratefully acknowledge the support of this work by Rank Precision Industries, Brentford, Middlesex, England.
The specific heat was measured from - 80°C to + 150°C with a differential scanning calorimeter (Perkin-Elmer D S C l ) (Figure 4). The volume specific heat at 25°C is Q = 3.5 ± 0.3 x 10^ Jm"^ K " ' and -the latent heat and transition entropy at Tc were
found to be AQ = 3.1 ± 0.3 x 10^ Jmole"^ and AS = 8.9 ± 0.5 Jmole"* K " * , respectively. Visual observation of the sample at the scanning speed ( 4 ° / m n ) showed
REFERENCES
1. C. B. Sawyer and C H . Towci, Phys. Rev. 35, 269 (1930).
2. I . Camlibel, / . Appl. Phys. 40,1690-3 (1969).
3. R. Sailer, Diploma thesis, University of the Saarland, Institute for Experimental Physics I I , Saarbriicken (1973).
4. A. P. Levanyuk and D. G. Sannikov, Fiz. Tverd. Tela 17, 526-30 (1975) [Sov. Phys. Solid State 17, 327-9 ( 1 9 7 5 ) ] . 5. J. Kobayashi, Y . Sato and H . Schmid, p/!>'i'. stat. sol. (a)
10, 259 (1972).
