Perovskites,
crystals and Ceramics
(september 2018)
|
36- Evidence
of magnetoelectric coupling in 0.9BiFeO3-0.1Ba [Ti0.95(Yb0.5Nb0.5)0.05]O3
ceramic (paper) A. Amouri,
S. Aydi, N. Abdelmoula, H. Dammak and H. Khemakhem,
Journal
of Alloys and Compounds 739
(2018) 1065-1079. DOI: 10.1016/j.jallcom.2017.12.101 The physical
properties of the Multiferroïc lead-free 0.9BiFeO3-0.1Ba[Ti0.95(Yb0.5Nb0.5)0.05]O3 ceramic
were investigated by in-situ Mössbauer
spectroscopy, X-ray diffraction (XRD), dielectric measurements and Raman
scattering. Both BiFeO3 and 0.9BiFeO3-0.1Ba[Ti0.95(Yb0.5Nb0.5)0.05]O3
ceramics underwent in-situ Mössbauer spectroscopy
in the temperature range of 300 K to 653 K and the parameters of hyperfine
interactions were determined. The magnetic transition temperature TN of our
doped sample was of 568 K, which was lower than that of BiFeO3 ... 35- Average
vs. local structure and composition-property phase diagram of K0.5Na0.5NbO3-Bi0.5Na0.5TiO3
system (paper) LJ. Liu, M. Knapp, H.
Ehrenberg, L. Fang, HQ. Fan, LA. Schmitt, H. Fuess,
M. Hoelzel, H.
Dammak, …, J. European Ceramic Society 37,
1387 (2017).
DOI: 10.1016/j.jeurceramsoc.2016.11.024 Phase diagram of the
solid solution system K0.5Na0.5NbO3- Bi1/2Na1/2TiO3
[(1-x)KNN-xBNT] has been
established from dielectric permittivity measurement and structure analyses.
The unit cell volumes continuously decrease depending on the composition,
while the local structure maintains distortions away from the cubic average
structure in the range 0.10 <= x <= 0.90. No clear correspondence for
the temperatures of phase transition exists between structural studies and
physical properties. The dielectric behavior is depicted successively from
normal ferroelectric, diffuse phase transition, re-entrant-like relaxor, relaxor + dipolar
glass-like relaxor, BNT-like relaxor
with the increase of BNT ... 34- Dielectric
evidence of persistence of polar nanoregions within the ferroelectric phases
of (1-x)Pb(Zn1/3Nb2/3)O3
- xPbTiO3 relaxor ferroelectric system (paper) M. A. Hentati,
H. Dammak, H. Khemakhem,
N. Guiblin and M. P. Thi.,
J. App. Phys. 113, (2015) 034104. DOI: 10.1063/1.4926877 The electromechanical
and structural properties of [001] and [111]-oriented PbZn1/3Nb2/3O3
-6% PbTiO3 (PZN - 6% PT) single crystals have been characterized using
dielectric spectroscopy, x-ray diffraction, depolarization current, and
piezoelectric techniques from 80K to 300 K. Both unpoled and poled samples
show a dielectric loss peak located in the range from 100 to 200 K. The poled
samples show a change in the slope of the real part of the dielectric
permittivity and a broad, frequency dependent peak in the imaginary part
below 200 K. In the same temperature range, we observed a broadening of the
Bragg peaks, fluctuations in the macroscopic polarization, and a change in
the rate of decrease in the elastic compliance and the d31
piezoelectric coefficient… 33- Role of
Zinc and Niobium in the Giant Piezoelectric Response of PbZn1/3Nb2/3O3
(paper) A. Al-Zein,
H. Dammak, P. Papet,
O. Mathon, B. Hehlen, C. Levelut, J. Haines, J. Rouquette,
Inorganic
Chemistry, 53 (2014) 3985. DOI: 10.1021/ic402409f Relaxor
ferroelectric perovskites are highly polarizable and can exhibit giant
coupling between elastic strain and an applied electric field. Here, we
report an in situ extended X-ray absorption fine structure (EXAFS) study of a
PbZn1/3Nb2/3O3 (PZN) single crystal as a
function of the electric field. We show that the strong dipoles in the NbO6
octahedra bonds are aligned along the four < 011 > directions close to
the orientation of the electric field, while a small reversible polar shift
occurs for Zn in the direction of the electric field, i.e., positive or
negative. This reversible Zn-O polar shift is proposed to play an important
role in both the "easy" switching of the ferroelectric polarization
and the giant piezoelectric effect in PZN. 32-
Dielectric properties and phase transitions of [001], [110], and [111]
oriented Pb(Zn1/3Nb2/3)O3-6%PbTiO3 single crystals (paper) M. A. Hentati,
H. Dammak, H. Khemakhem
and M. P. Thi., J. App. Phys. 113, (2013) 244104. DOI:
10.1063/1.4812327 Phase transformations
of [001], [110], and [111] oriented Pb(Zn1/3Nb2/3)O3-6%PbTiO3 (PZN-6%PT)
single crystals have been investigated by means of dielectric permittivity
and loss, x-ray diffraction and depolarization current as function of
temperature (from 250 to 500 K). The unpoled samples undergo R-T-C phase
transition sequence during zero field heating (ZFH), where R, T, and C are
rhombohedral, tetragonal, and cubic phases, respectively. Under electric
field (0.5 kV/cm), an intermediate orthorhombic (O) phase is induced between
the T and R phases in the field cooling (FC) process. This phase reappears
during subsequent zero field heating of the poled sample (zero field heating
after field cooling: ZFHaFC). The existence range
of this O phase depends on both the crystal orientation and the measurement
conditions (FC or ZFHaFC). Finally, for the [001]
direction, it was found that the piezoelectric activity of the intermediate
phase is the highest. 31-
Dielectric characteristic of nanocrystalline Na0.5K0.5NbO3 ceramic
green body (paper) L. Liu, H.Q. Fan, L. Fang,
H. Dammak and M. P. Thi., J. Electroceramics,
28 (2012) 144. DOI: 10.1007/s10832-012-9695-6 30-
Orthorhombic to tetragonal structural phase transition in Na0.5K0.5NbO3-based
ceramics (paper) L. Liu, Y.M. Huang, Y.H.
Li, L. Fang, H. Dammak, H.Q. Fan
and M. P. Thi., Material Letters, 68 (2012)
300. DOI: 10.1016/j.matlet.2011.10.103 29- Effect of mechanical activation on the structure
and ferroelectric property of Na0.5K0.5NbO3 (paper) L. Liu, M. Wu, Y. Huang,
L. Fang, H. Fan, H. Dammak and M.
P. Thi., Mater. Res. Bull. 46 (2011) 1467.
DOI: 10.1016/j.materresbull.2011.05.001 28- Intrinsic effect of Mn doping in PZN-12%PT
single crystals (paper) M. A. Hentati, M. Guennou, H. Dammak, H. Khemakhem
and M. Pham Thi, J. App. Phys. 107 (2010) 064108. DOI: 10.1063/1.3331817 In this work we
study the influence of manganese doping on the electromechanical properties
of PZN–12%PT single crystal. The full electromechanical tensor of doped
PZN–12%PT in the tetragonal single domain state is determined by the
resonance-antiresonance method. Doping leads to a decrease in the dielectric
transverse permittivity e_11 and of the shear piezoelectric coefficient d15. We show by dielectric constant e_33
measurements that the single domain state in doped crystal is
stable in plates as thin as 90 mm, whereas it was unstable in plates thinner than
300 mm for the undoped crystals. This intrinsic effect is
discussed by using a volume effect model based on the symmetry conforming
principle of point defects. [Ren, Nature Mater. 3, 91 (2004)]. Mn doping forces the stability of PZN–12%PT single
domain state, which makes the doped crystal a most suitable candidate than
the pure crystal for high frequency ultrasonic medical imaging probe. 27- Grain size effect on electromechanical
properties and non-linear response of dense nano
and microstructured PIN-PT (paper) K. Alilat, M. Pham Thi, H. Dammak,
C. Bogicevic,A.
Albareda, M. Doisy, J.Eur. Crem. Soc. 30
(2010) 1919-1924. DOI:
10.1016/j.jeurceramsoc.2010.03.010 26- Effects of
Na/K evaporation on electrical properties and intrinsic defects in
Na0.5K0.5NbO3 ceramics L. J. Liu, H. Q. Fan, L. Fang, X. L. Chen, H. Dammak, M. PhamThi.
Mater.
Chem. Phys. 117 (2009) 138. DOI:
10.1016/j.matchemphys.2009.05.024 (paper) |
25- Non Linear
Properties of Dense PIN-PT Ceramics
Mai Pham Thi, Karima Allilat,
Hichem Dammak, Laurent Lebrun, Martine Doisy
24- Electromechanical
properties of single domain PZN–12%PT measured by three different methods
Mael Guennou, Hichem
Dammak, Philippe Djémia, Philippe Moch, Pham-Thi Mai
M. Guennou, H. Dammak
and M. Pham Thi
T. Delaunay, E. Le Clézio, M. Guennou, H. Dammak,
M. Pham Thi, G. Feuillard
Haixia Wang, H.
Dammak, Philippe Gaucher and
20- Étude du frittage non-conventionnel de céramiques de
type YAG:Nd en présence d’ajout de silice
C.
Sallé, A. Maître, J.F. Baumard, Y. Rabinovitch, C. Bogicevic,
Matériaux & Techniques 95, 241-249 (2007)
19- Freeze – Dried
Nanometric Neodymium doped YAG Powders for Transparent Ceramics
Y. Rabinovitch, C. Bogicevic, F. Karolak, D. Tétard, H. Dammak
Journal of materials processing
technology, 199 (2008) 314-320 (5 pages)
M. El Marssi and H. Dammak
Polarized Raman spectra
measurements have been performed on oriented single crystals of Pb[(Zn1/3Nb2/3)0.955Ti0.045]O3 (PZN-4.5%PT)
and Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3
(PZN-9%PT) poled by an electric field along the 
pseudo-cubic direction in order to determine the
nature of the induced ferroelectric phases. Under field-cooled (FC) conditions
the ferrolectric phase transition sequence,
tetragonal-orthorhombic-rhombohedral, was observed in PZN-4.5%PT. Comparison beween the phase transitions induced in PZN-9%PT and
PZN-4.5%PT crystals in FC shows that the low temperature ferroelectric phase in
PZN-9%PT can not be orthorhombic and it can be
attributed to the monoclinic phase. The characteristic temperatures found by
Raman spectroscopy correspond to those obtained by dielectric measurements and
by X-ray diffraction reported previously.
17. Thickness
dependence of electromechanical properties of PZN-xPT
single crystals :
H. Dammak, M. Guennou, C. Ketchazo, M. Pham-Thi, F. Brochin, T. Delaunay, P. Gaucher, E. Le Clézio
and G. Feuillard, 15th IEEE
International Symposium on Applications of Ferroelectrics, July 30 to
August 02, 2006, Page(s):249 - 252. article
We studied the electromechanical
properties of PMN-PT and PZN-PT single crystal plates poled along [001] with
thickness t ranging from 800 down to 70 mm. In the case of the tetragonal
single domain state (1T), the properties of the thickness mode remain stable
down to 250 mm. Below 250 mm, an instability of the polarization
is shown. The plates exhibit regions where polarization lies in the plane
of the plates. These emergence of these regions results in an additional shear
mode at a frequency close to that of the thickness mode, an important increase
of the dielectric constants eS33 and eT33 and a decrease of the
coupling-factor kt and longitudinal
wave velocity vD33t. In the rhombohedral
multidomain state (4R) a moderate variation of kt
can be observed while eS33 increases with decreasing thickness.
The increase of the dielectric constant in the 4R state is also related to an
additional shear mode. When t decreases, the volume ratios of each
domain family are not equal, leading to a tilt of the average spontaneous
polarization away from the poling electric field. Consequently the modification
of the domain structure for thin plates leads to a change of the electromechanical
properties.
16. Role
of Mn doping on the Electromechanical Properties of [001] Domain Engineered
Single crystals :
M. Guennou, H. Dammak, M. Pham-Thi and P. Gaucher, 15th IEEE
International Symposium on Applications of Ferroelectrics, July 30 to
August 02, 2006, Page(s):265 - 268, article
We studied the influence
of Mn doping on electromechanical properties of PZN-xPT with x = 7% and 9%.
Single crystals oriented along the [111], [011] and [001] directions were poled by a "field cooling" process with an
applied electric field of 1 kV/cm. It is shown that Mn doping has a significant
influence on the single domain crystals in both cases. It modifies the phase
symmetry of single domain PZN-7PT from orthorhombic to
rhombohedral. It reduces permittivity perpendicular to polarization direction
of single domain PZN-9PT by about 40%. This change in the
properties of the bulk material is the main cause for the decrease of permittivity
observed in [001] poled PZN-9PT crystals. Further effects of doping
on the properties of [001] domain engineered crystals are a decrease of the
piezoelectric coefficient, a hardening of the material and an increase of the
mechanical quality factor.
15. Fine
grains ceramics of PIN-PT, PIN-PMN-PT and PMN-PT systems: Drift of the
dielectric constant under high electric field :
M. Pham-Thi, C. Augier,
H. Dammak and P. Gaucher, Ultrasonics. 44 (2006) e627-e631 (5 pages). World Congress On Ultrasonics (WCU), 28-September 1st ,
2005
Lead-based ferroelectric
ceramics with (1-x)Pb(B1 B2)O3–xPbTiO3 formula have emerged as a group of
promising materials for various applications like ultrasonic sonars or medical
imaging transducers [Y.H. Chen, K. Uchino, J. Appl. Phys. (2001) 3928–3933].(1-x)PMN–xPT,
(1-x)PIN–xPT
and ternary solutions xPIN–yPMN–zPT ceramics are synthesised using the solid state reaction
method [Y. Hosono, Y. Yamashita, H. Sakamoto, N.
Ichinose, Jpn. J. Appl. Phys. 42 (2003) 5681–5686].
Our objective is to achieve higher structural transition temperatures
than those of PMN–PT ceramics with as good dielectric, piezoelectric and
electromechanical properties. Ceramics capacitance and
loss tangent are measured when the ac field of measurement increases up to E = 0.5 kV/mm. Behaviours of these materials under ac
field are related to their coercive field and Curie temperature.
14. Easy
induction of a ferroelectric fourfold monoclinic domain state from a tetragonal
ferroelectric monodomain state in PbZn1/3Nb2/3O3.:
A. Lebon, H. Dammak and G. Calvarin , J. Phy :
Condens. Matter. 17 (2005) 6385-6391 (7 pages).
article
We report a combined
pyroelectric, dielectic and structural characterization
of PZN single crystals in field cooling (FC) run along [001]. The pyroelectric
current and the dielectric permittivity show a new characteristic temperature,
at T » 370 K, related to a macroscopic competition
between two induced ferroelectric tetragonal (T) and monoclinic (M) phases. The
phase transition, which starts around TC-R = 385 K, spreads
over a large temperature range and some amount of T-phase is still observed at
room temperature (RT). The M-T phase mixture, induced below TC-R,
is stable after field removal. According to a previous Raman scattering work, a
fourfold symmetry of M-domains is proposed; the residual T-phase is stabilized by
the coexistence of four symmetry-allowed M-domains arranged around [001]. Our
results confirm the flatness of the free energy of relaxor-ferroelectrics
and their capability to zap from one polar order to another as a function of the
poling direction and of the temperature range.
13.
Frequency dependence of electromechanical properties
of PZN-xPT single crystals: article
T. Delaunay, E. Le Clézio, H. Dammak, P. Gaucher, M. Pham Thi, M. Lethiecq and G. Feuillard
Journal de Physique IV , 128 (2005) 161-167. (7 pages)
In this paper, the
frequency behaviour of electro-mechanical properties of PZN-xPT
single crystals with compositions close to the morphotropic phase boundary is
studied at frequencies up to 100 MHz. Properties are
deduced from the fit of the electrical input impedance, theoretically
calculated with the KLM equivalent circuit model, to experimental data. To
measure the electrical impedance of a crystal, its surfaces have first to be
metallized. For very thin samples, this metallization may influence the
resonances and alter the property identification. A theoretical study is thus
performed to quantify the influence of the electrodes on the crystal
vibrations. The results show that, even for high frequencies, their effects are
negligible. In a second part, the evolution with frequency of the single
crystal characteristics is studied. The properties are identified in a
frequency bandwidth centered on the resonances, from
the fundamental to the 21th harmonic. The study shows the stability
of the electromechanical properties versus the frequency. Finally, the
mechanical and dielectric loss tangents are quantified.
12. Phase
diagram of high Tc Pb(In1/2Nb1/2)O-3-PbTiO3 ceramics: article
C. Augier, M. Pham Thi,
Hichem Dammak and P. Gaucher
Journal of the European Ceramic
Society 25 (12): 2429-2432 (2005) (4 pages).
Dense (1-x)Pb(In1/2Nb1/2)O3-xPbTiO3
ceramics were synthesised by hot forging and thermal grain growth. (1-x)PIN-xPT phase diagram was investigated by X-ray diffraction and
dielectric meausurements. The morphotropic phase boundary
zone was found to be between a rhombohedral phase region for low PT contents
and a tetragonal phase region for high PT contents, i.e. in the 0.34-0.39 x
range. A mixture of tetragonal and probably monoclinic phases was observed for x=0.37
at room temperature.
11. Electric
field induced orthorhombic phase in PZN-4.5%PT single crystals
: article
A-E. Renault, H.
Dammak, G. Calvarin, P. Gaucher and M. Pham Thi.
J. Appl. Phys. 97(4), 044105 (2005)
(6 pages).
The ferroelectric
phase transition sequence of [
01], [001] and [111]-oriented PZN-4.5%PT single crystals was investigated,
between 300 and 450 K, as a function of E-field applying protocol.
At zero E-field, PZN-4.5%PT exhibits the following phase transitions:
cubic (C)®tetragonal (T)® Rhombohedral (R), in cooling run. Dielectric
and X-ray diffraction combined measurements, performed under E-field on
a [01]-oriented single crystal, show that
an intermediate orthorhombic (O) ferroelectric phase is induced between the T
and R ones. The temperature range of the induced O phase depends strongly both
on the direction and on the protocol (FC, ZFHaFC or
FH) of E-field applying. When E-field is applied along [01], it varies from 40K (FC under 100kV/m)
to 15 K (ZFHaFC); when E-field is applied
along [001] or [111], it is much narrower (< 15 K), to such an
extent that the O phase is not observed in FH for [001] and in FC for [111].
10. Orientation
Distribution and Fiber Texture of Highly Oriented
Piezoceramics: PMN-PT System: article
M. Pham Thi, H. Hemery, O. Durand and Hichem Dammak
Japanease Journal of Applied Physiscs: 43(12) (2004) 8190 (5 pages).
Textured (1-x)PbMg1/3Nb2/3-(x)PbTi03, (PMN-xPT), ceramics were synthesised by homo-epitaxial template grain
growth (HTGG) using PMN-PT nano-particles and cubic
templates. Orientation of the templates was obtained during tape casting. The
texture fraction of ceramics was estimated by the Lotgering
method at RT and above Tc. Textured Tape Cast Ceramics display quasi complete (001)
texture (f=0.99) in the cubic phase. The (111) pole figure reveals (001) fibre
texture in accordance with optical observation. The texture was obtained in all
the volume and only small misorientation was observed.
9.Origin
of the Giant Piezoelectric Properties in the [001] Domain Engineered Relaxor Single Crystals : article
H. Dammak, A.-E.
Renault, P. Gaucher, M. Pham Thi and G. Calvarin
Japanease Journal of Applied Physiscs : 42(10) (2003) 6477-6482.
Relaxor single crystals PZN-9%PT have been cut
and poled along [
01] direction for which the
spontaneous polarization Ps is approximately parallel
to the poling field Ep. The piezoelectric
matrix of the monoclinic single-domain (1M state) has been determined, in the approximation
of an orthorhombic symmetry. The shear mode (15) along [101], gives the highest
electromechanical coupling factor k15 (>80%) and
the largest piezoelectric coefficient d15 (~3200 pC/N). The properties of the disoriented 1M state have been
calculated from a change of axes. The maximum of 
is obtained along a direction
close to [001]. This is due to the very large value of d15 compared
to d33 in the basic 1M state. On the other hand the transverse
piezoelectric coefficient along [uv0] for the [001] disoriented Ps
single domain presents a strong anisotropy. Finally, in the [001] domain
engineered configuration, an important extrinsic contribution of the domain
coexistence is evidenced by comparing calculated and measured coefficients.
8.Tetragonal
and rhombohedral induced polar order from the relaxor
state of PbZn1/3Nb2/3O3 : article
A. Lebon, H. Dammak and G. Calvarin
J. Phy :
Condens. Matter : Vol 15, 3069 (2003).
Structural and dielectric
characterizations of the relaxor ferroelectric PbZn1/3Nb2/3O3
(PZN) were carried out on single crystals in the temperature range of the
dielectric anomaly (370 K< T < 440 K), under dc-electric field applied
along [001] and [111] directions. Two ferroelectric phases, tetragonal (T) and
rhombohedral (R), can be field induced in this temperature range, the symmetry
of which depends on the direction of the applied field, [001] and [111]
respectively. (E-T) diagrams were built and interpreted under the consideration
of polar nano regions (PNR) with a prominent
tetragonal component. These PNRs prevent the onset of a monodomain state when
the field is applied along [111] and explain the features of PZN for an applied
field along [001]: large lattice strain, easy onset of the T phase and
suppression of the dielectric relaxation for (E ³ 1.5 kV.cm-1). The microscopic
origin of these PNRs could be discussed in relation with recent NMR and
structural results reported in other isomorphous relaxors.
7.Cationic
competition induces monoclinic phase in high piezoelectric PSN-PT compounds
R. Haumont, B. Dkhil, J.M. Kiat, A. Al-Barakaty, H. Dammak,
and L. Bellaiche
Phys. Rev B : 68 (2003) 014114
A global picture for
the structural evolution in the relaxor -ferroelectric
solid solution (PbSc1/2Nb1/2O3)1-x-(PbTiO3)x, namely PSN-PT is proposed. Thanks to
X-Ray profile analysis and Rietveld neutrons powder refinement, a monoclinic phase
has been evidenced in the morphotropic region (i.e. x»0.43). This lower symmetry phase ‘bridges’
the rhombohedral Ti-poor phase (x
0.26) with the tetragonal Ti-rich phase
(x
0.55), in a similar way as in PMN-PT
or PZN-PT. For weak titanium concentration, we observe a macroscopic
rhombohedral state with local monoclinic symmetry resulting from the
combination between Pb and Sc/Nb/Ti shifts along [001] and [111] directions respectively. Cationic
competition with Ti-doping increases the coherence length of this short ranged
monoclinic phase which becomes long ranged in the morphotropic region. This
intermediate monoclinic phase is in complete agreement with our first-principles
calculations which predict a Pm or a Cm space groups. It has been showed that
these ones are very close to each other in the free energy space, and a minor
change of atomic distribution and/or a slight modification in composition is
enough to alter the space group of the monoclinic ground-state. Finally, in
Ti-rich region, the monoclinic ground state is destroyed in favor
of a tetragonal phase. Random fields due to the cationic distribution and the
competing orderings of the polarization along multiple direction on a mesoscale
are found to play a key role on the ground states and their associated
electromechanical properties.
6.Domain Engineering of PZN-9%PT Single Crystals and
Piezoelectric Related Properties: article
A-E. Renault, H. Dammak, P. Gaucher, M. Pham Thi
and G. Calvarin
IEEE catalog number 02CH37341, pp 439-442, Proceeding
of the 2002 13th IEEE, ISAF, (International
Symposium on the Applications of Ferroelectrics) Nara, JAPAN, May 28-June
1, 2002, Editors: Grady White and Takaki Tsurumi.
The domain configuration
and the electromechanical related properties have been studied in Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZN-9%PT)
single crystals cut along [001] and 
. It was established that soft (with
high d) and hard (with lower d) piezoelectric properties are respectively
obtained in a multidomain and a single domain configuration. The softer
piezoelectric material (d33 = 2700 pC/N,
= 180 pN/m2, k33 = 93%) was found
in the monoclinic multidomain state after poling with a small field along [001].
Optimal poling process and electromechanical related properties of the single
crystals were discussed in term of the field-temperature diagram.
5.The
cubic to rhombohedral phase transition of Pb(Zn1/3Nb2/3)O3 :
a high-resolution X-ray diffraction study on single crystals : article
A. Lebon,
H. Dammak, G. Calvarin, I. Ould
Ahmedou
J. Phy :
Condens. Matter., Vol. 14.(2002)
7035-7043.
The cubic to
rhombohedral (C-R) phase transition of the ferroelectric-relaxor
Pb(Zn1/3Nb2/3O3)
(PZN) is investigated using high-resolution X-ray diffraction on single
crystals. The phase transition is diffuse and spreads over the temperature
range TCR = 385 ± 5 K – TR = 325 ± 5 K. Below TCR, the
cubic phase transforms progressively into rhombohedral domains the average size
of which, about 60-70 nm in the [111] direction, remains unchanged as
temperature is lowered, so no growth of the R-domains is observed. At TR,
the nanometric R-domains fully pave the crystal but structural mismatches
between adjacent domains generate stresses, which increase as temperature is
lowered. The anomalous broadening of diffraction peaks of the R-phase, which
originates from size and strain effects, can be suppressed by applying a
dc-electric field, along the [111] direction, which transforms the polydomain
state into a rhombohedral quasi-monodomain state.
4.Domain structures in Monoclinic PZN-9%PT poled single crystals: article
A-E. Renault, H. Dammak, G. Calvarin, M. Pham Thi and P. Gaucher.
Japanease Journal of Applied Physiscs, 41 (2002) pp 1-5.
A tetragonal (T) « monoclinic (M) phase
transition characterized by a wide thermal hysteresis is observed in PZN-PT
single crystals close to the morphotropic composition PZN-9%PT. The domain
structure of crystals, determined by x-ray diffraction and optical
observations, is dependent on the poling crystallographic direction. A
monoclinic quasi single-domain structure is obtained by poling along the
pseudo-cubic [10] direction whereas an unexpected monoclinic
multi-domain state with macroscopic 2mm symmetry can be obtained for [001]
poled crystals. Finally it is shown that the largest piezoelectric response
corresponds to the monoclinic multi-domain state of [001] poled crystals.
3.Translational and orientational order in
Lead Zinc Niobate : an optical and Raman study : article
A. Lebon, M. El Marssi,
R. Farhi, H. Dammak and G. Calvarin
J. Appl. Phys. Vol 89, Issue 7, (2001) pp
3947-3954.
Raman and optical
experiments have been performed on a lead zinc niobate
(Pb(Zn1/3Nb2/3)O3 or PZN) single crystal oriented
along (111) under zero field cooling (ZFC), and zero field heating after field
cooling (ZFH/FC) conditions. At high temperature, the Raman spectra originate
from a phonon-polarization coupling whose selection rules depend upon the
wavevector of the quasi-static polarization, and that activates modes in the
entire Brillouin zone. At room temperature, ferroelectric macro-domains were
induced and stabilized under field cooling conditions. Their optically
uniaxial behavior along [111], reflects a
rhombohedral orientational order. However, Raman
analysis shows that a zone center line assignment on
the basis of the C3v point group is not appropriate, because of
translational symmetry breaking due to chemical and structural disorder. Raman spectroscopy was also performed on a single
crystalline sample of PZN oriented along (001). Raman measurements evidence the
similarity of the spectra for both crystals in the paraelectric phase. This
confirms the idea of a second order-like process. At room temperature, this
crystal configuration, with a dc electric field parallel to [001], is found
according to Raman experiments to give way to an equivalent distribution of the
four rhombohedral domains selected by the applied electric field.
2. Kinetic study of PZN polarization under a static
electric field (article)
H. Dammak, A. Lebon and G. Calvarin
Ferroelectrics vol 235 (1999) 151-158 (Proceeding of the
second international seminar on Relaxor
Ferroelectrics (ISRF II).
1 EXISTENCE
OF A DIRECT PHASE-TRANSFORMATION FROM HEMATITE TO MAGHEMITE
.
Hichem DAMMAK