structural and dielectric properties of na1−x ba x nb1−x (sn0.5ti0.5) x o3 ceramics

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1 23 Journal of Materials Science Full Set - Includes `Journal of Materials Science Letters' ISSN 0022-2461 Volume 47 Number 4 J Mater Sci (2012) 47:1943-1949 DOI 10.1007/s10853-011-5987-5 Structural and dielectric properties of Na 1−x Ba x Nb 1−x (Sn 0.5 Ti 0.5 ) x O 3 ceramics H. Khelifi, A. Aydi, N. Abdelmoula, A. Simon, A. Maalej, H. Khemakhem & M. Maglione

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Journal of Materials ScienceFull Set - Includes `Journal of MaterialsScience Letters' ISSN 0022-2461Volume 47Number 4 J Mater Sci (2012) 47:1943-1949DOI 10.1007/s10853-011-5987-5

Structural and dielectric properties ofNa1−x Ba x Nb1−x (Sn0.5Ti0.5) x O3 ceramics

H. Khelifi, A. Aydi, N. Abdelmoula,A. Simon, A. Maalej, H. Khemakhem &M. Maglione

1 23

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Structural and dielectric propertiesof Na12xBaxNb12x(Sn0.5Ti0.5)xO3 ceramics

H. Khelifi • A. Aydi • N. Abdelmoula •

A. Simon • A. Maalej • H. Khemakhem •

M. Maglione

Received: 3 June 2011 / Accepted: 21 September 2011 / Published online: 5 October 2011

� Springer Science+Business Media, LLC 2011

Abstract Lead-free (1 - x)NaNbO3/xBa(Ti0.5Sn0.5)O3 (x =

0.1, 0.125, 0.15, 0.175, 0.2, and 0.3) ceramics were elaborated by

the conventional ceramic technique. Sintering has been

made at 1523 K for 2 h. The crystal structure was investi-

gated by X-ray diffraction with CuKa radiation at room

temperature. As a function of composition, these compounds

crystallize with tetragonal or cubic symmetry. Dielectric

measurements show that the materials have a classical fer-

roelectric behavior for compositions in the range 0.10

B x B 0.15 and relaxor one for compositions in the range

0.15 \ x B 0.30. Temperatures TC or Tm decrease as x con-

tent increases. The ferroelectric behavior has been confirmed

by hysteresis characterization. For x = 0.1, a piezoelectric

coefficient d31 of 42.146 pC N-1 was obtained at room

temperature. The evolution of the Raman spectra was studied

as a function of temperature for x = 0.1.

Introduction

Relaxor ferroelectrics are considered promising materials

for use in modern devices such as capacitors, sensors,

information storage devices, and optical modulators [1].

However, most typical relaxors are lead-based perovskite

compounds, which are environmentally unfriendly because

of the toxicity of lead [2, 3]. Recently, many studies have

been carried out on the lead-free relaxors [4–6].

Sodium niobate is a dielectric material of the perovskite

group. This material undergoes several phase transitions as

the following [7]:

Cubic��!914 Ktetragonal��!842 K

orthorhombic��!173 Krhombohedral:

At room temperature, NaNbO3 (NN) is antiferroelectric

[7, 8] and becomes ferroelectric by mixing with even a

small amount of KNbO3 [9, 10], LiNbO3 [11, 12], BaSnO3

[13], and SrSnO3 [14].

BaTi1-xSnxO3 are basically suitable as environmentally

friendly materials used for capacitor ceramic, dielectric

amplifier, switching circuit snubbers, sensor [15–17], and

in functionally graded materials [18].

In addition, several studies have shown that the partial

replacement of titanium by tin in BaTi1-xSnxO3 (BTSx) sys-

tem improves the dielectric behavior [19, 20]. As, increasing

Sn-content, the temperature TC of the paraelectric–ferroelec-

tric phase transition decreases considerably. Besides, the

analysis of temperature dependent permittivity data taken at

various frequencies revealed characteristic features of relaxor

ferroelectrics for x C 0.2 [21]. However, Boudaya et al. [22]

have shown that the replacement of titanium by tin in ceramics

Ba0.1Na0.9(Ti1-ySny)0.1Nb0.9O3 with 0 B y B 1 induces a

decrease in Curie temperature without relaxor behavior.

Therefore, in this study we report on the structural and

the relaxor behavior of Na1-xBaxNb1-x(Sn0.5Ti0.5)xO3 system

(0.1 B x B 0.3) obtained by mixing NN with Ba(Ti0.5

Sn0.5)O3. The ferroelectric and piezoelectric properties of the

sample with x = 0.1, characterized by the best density (of

about 93% of the theoretical one), are reported. Raman

spectroscopy characterization for x = 0.1 is also carried out.

H. Khelifi � A. Aydi � N. Abdelmoula (&) � A. Maalej �H. Khemakhem

Laboratoire des Materiaux Ferroelectriques, Unite de recherche

Physique-Mathematiques, 05/UR/15-04, Faculte des Sciences de

Sfax, Universite de Sfax, B.P. 1171, 3000 Sfax, Tunisie

e-mail: [email protected]

A. Simon � M. Maglione

CNRS, Universite de Bordeaux, ICMCB,

87 avenue Dr. A. Schweitzer, Pessac 33608, France

123

J Mater Sci (2012) 47:1943–1949

DOI 10.1007/s10853-011-5987-5

Author's personal copy

Experimental

Na12xBaxNb12x(Sn0.5Ti0.5)xO3 ceramics with various

compositions (x = 0.10, 0.125, 0.15, 0.175, 0.2, and 0.3)

were prepared by solid-state synthesis using the following

chemical reaction:

ð1�xÞ2

Na2CO3 þ xBaCO3 þð1�xÞ

2Nb2O5 þ

x

2TiO2

þ x

2SnO2 ! Na1�xBaxNb1�xðSn0:5Ti0:5ÞxO3

þ ð1�xÞ2

CO2 " :

The starting materials are BaCO3, Na2CO3, Nb2O5, TiO2,

and SnO2 (99% purity). They have been thoroughly mixed in

agate mortar for 1 h and calcined at 1300 K for 12 h. After

calcination, powders have been mixed for 1 h and pressed

under 100 MPa into disks of 8 mm in diameter and about

1 mm in thickness. These pellets have been sintered at

1523 K for 2 h in air atmosphere. The densities of the

sintered samples were 90–93% of the theoretical values. The

diameter shrinkages of ceramics disks were systematically as

(/init - /fin)//init (/init and /fin represent initial and final

diameter, respectively). Their values are between 0.15 and

0.18. Microstructure of the samples was observed by

scanning electron microscopy (SEM, JSM EMP-2300).

Average grain size is found to vary from 1 to 2 lm

depending on composition x. Figure 1 shows repre-

sentative SEM micrograph of the surface of Na0.9Ba0.1

Nb0.9(Sn0.5Ti0.5)0.1O3 ceramic as an example.

The phase structure of the ceramics sample Na1-x

BaxNb1-x(Sn0.5Ti0.5)xO3 was determined using a Philips

PW 3040/00 XPERTMPD diffractometer using CuKaradiation (k = 1.5406 A).

X-ray diffraction (XRD) data at room temperature were

performed on the milled ceramic powder data and were

collected over the angular range 10� B 2h B 80� with 10 s

counting time for each step of 0.02.

The dielectric measurements were performed under dry

helium on ceramic disks after deposition of golden elec-

trodes on the circular faces by cathodic sputtering. The

dielectric permittivity er0 was determined under helium

atmosphere as a function of temperature (80–600 K) and

frequency (102–2 9 105 Hz) using a Wayne–Kerr 6425

component analyzer. All the dielectric data were collected

while heating at a rate of 2 K min-1.

Results and discussion

XRD analysis

The XRD patterns were analyzed to confirm the symmetry

and to calculate the lattice parameters for (1 - x)NaNbO3/

xBa(Ti0.5Sn0.5)O3 samples. The values of the lattice and

profile parameter were determined using a global profile-

matching method with the software ‘‘Fullprof’’ [23]. All

the reflexion peaks of the X-ray profiles were indexed with

only one perovskite-type phase. The observed, calculated,

and the difference of the XRD patterns for ceramics with

composition x = 0.1 and x = 0.2 were shown in Fig. 2 as

examples.

The symmetry of the ceramic specimens appears to be a

small tetragonal distortion for compositions in the range

x B 0.15 and cubic for in the range 0.15 \ x B 0.3. For

x [ 0.3, the sample was not in single phase. The variation

of unit cell parameters a and c and volume V of the

Na12xBaxNb12x(Sn0.5Ti0.5)xO3 ceramics are plotted in

Fig. 3.

The regular increase of these parameters should be related

to the increase of ionic radii: r(Na?, C.N. = 8) = 1.18 A

and r(Nb5?, C.N. = 6) = 0.64 A for NN quite lower than

r(Ba2?, C.N. = 12) = 1.61 A, r(Ti4?, C.N. = 6) = 0.605 A,

and r(Sn4?, C.N. = 6) = 0.69 A (0.5 r(Ti4?) ? 0.5 r(Sn4?)

= 0.647 A) [24] in BTS.

Dielectric studies

The temperature dependence of the real (er0) and the imaginary

(er00) parts of the dielectric permittivity of Na1-xBaxNb1-x

(Sn0.5Ti0.5)xO3, for x = 0.1, 0.125, 0.15, 0.175, 0.2, and 0.3

samples exhibit two different behaviors, depending upon the

substitution rate. In fact, for x = 0.1, the ceramic shows

conventional ferroelectric behavior, with three dielectric

anomalies originate from structural phase transitions which

are known to exist in NN [7] (rhombohedral–orthorhombic at

T2, orthorhombic–tetragonal at T1, and tetragonal–cubic at TC)

(Fig. 4). The TC value corresponding to the paraelectric–fer-

roelectric phase transition does not depend on the frequency.Fig. 1 SEM micrograph of the surface of Na0.9Ba0.1Nb0.9

(Sn0.5Ti0.5)0.1O3 ceramic

1944 J Mater Sci (2012) 47:1943–1949

123

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In addition, the TC value gets to a lower temperature and T1

and T2 to higher temperatures with the substitution of Na by Ba

and Nb by Sn and Ti. Moreover, for x B 0.15, the temperature

dependence of 1/er0 at 103 Hz showed that the Curie–Weiss

law 1/er0 = (T - T0)/C is followed and that the paraelectric–

ferroelectric phase transition is of premier order, since the

Curie temperature T0 is slightly lower than the transition

temperature TC (TC - T0 = 2 K) (Fig. 4). All these obser-

vations characterize a classical ferroelectric behavior for all

compositions in the range x B 0.15.

For compositions in the range x [ 0.15, only one broad

peak occurs at Tm, with frequency dispersion at tempera-

tures below Tm (T \ Tm) for the real part and at T [ Tm for

the imaginary part (Fig. 5). The value of Tm is frequency

dependent, unlike that of TC, as in classical ferroelectrics.

Tm was found to shift to higher values and er0 decreased as

the frequency increases. For higher frequencies, the tem-

perature, Tm of the maximum of er0 shifts to higher values.

However, the maximum of er00 increases with the frequency

increasing. In addition, there is a large amount of deviation

from the Curie–Weiss law, which is not observed for a

classical ferroelectric. The value of Curie–Weiss temper-

ature T0 was greater than that of Tm. The observed tem-

perature and frequency dependence of er0 and er

00 is specific

Fig. 2 X-ray diffraction patterns for a tetragonal and a cubic

ceramics with compositions x = 0.1 and x = 0.2 in Na1-xBaxNb1-x

(Sn0.5Ti0.5)xO3

Fig. 3 Variations of the lattice parameters and cell volume versus

composition for Na1-xBaxNb1-x(Sn0.5Ti0.5)xO3 ceramics

0

3000

6000

9000

100 200 300 400 500 6000.000

0.001

0.002

0.003

0.004

0.005

1/ ε'r (1 kHz)

T0 TC = 466K

T2 = 254K

T1 = 385K

T(K)T0

ε' r

0.1kHz 0.5kHz 1 kHz 5 kHz 10 kHz 50 kHz 100 kHz 200 kHz

T(K)0 100 200 300 400 500 600

0 100 200 300 400 500 6000

100

200

300

400

500

ε'' r

0.1kHz 0.5kHz 1 kHz 5 kHz 10 kHz 50 kHz 100 kHz 200 kHz

T(K)

Fig. 4 Temperature and frequency dependences of er0 and er

00 and

temperature dependence of 1=e0r at 103 Hz (the symbols: experimental

data; the solid line: fitting to the Curie–Weiss law) for

Na0.9Ba0.1Nb0.9(Sn0.5Ti0.5)0.1O3 (x = 0.1) ceramic

J Mater Sci (2012) 47:1943–1949 1945

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to a relaxor behavior. The sample with x = 0.2 presents a

DTm = Tm (105 Hz) - Tm (102 Hz) of about 10 K at

Tm = 200 K. The relaxor behavior can be induced by

many reasons such as a microscopic region, the merging of

micropolar regions into macropolar regions [25], local

compositional fluctuation [26], superparaelectric [27],

and dipolar glass model [28]. In our solid solution

(1 - x)NaNbO3 - xBa(Sn0.5Ti0.5)O3, Na? and Ba2? ions

co-occupy the A-site of ABO3 perovskite structure, Nb5?

and Sn4? and Ti4? ions co-occupy the B site; therefore, the

cations disorder in perovskite unit cell should be one of the

reasons for the appearance of relaxor state. On the other

hand, it is known that the NN shows antiferroelectric at

room temperature [7]. The partial heterogeneous substitu-

tion of NN by Ba(Sn0.5Ti0.5)O3 (x B 0.15) make these

ceramics ferroelectric. For x [ 0.15, the macrodomain

formed in (1 - x)NaNbO3 - xBa(Sn0.5Ti0.5)O3 should be

divided into microdomains with increasing Ba2? and Sn4?

and Ti4? ion doping, which also may result in the

appearance of the more relaxor-like behavior.

The frequency dispersion of the er0 = f(T) maxima in

relaxor ferroelectrics has been attributed to the distribution

of relaxation times. A large number of theoretical models

have been proposed to understand the diffusiveness and the

dispersion. The Vogel–Fulcher model has been considered

to be the most successful mathematical representation for

the divergent nature of relaxation time below certain

temperature [29, 30]. The observed frequency dependence

of Tm was empirically evaluated using Vogel–Fulcher’s

relationship given as:

f ¼ f0exp �Ea=kB Tm � TVFð Þð Þ

where the activation energy Ea is determined by the

potential barrier for the relaxing particle to jump out of the

potential well, TVF the static freezing temperature of

polarization fluctuation. The pre-exponential factor f0 is the

Debye frequency and kB is the Boltzmann constant. We

fitted all the dielectric data of relaxor compounds to this

Vogel–Fulcher equation. The values of Ea, TVF, and f0 for

x = 0.175, x = 0.2, and x = 0.3 were summarized in

Table 1. It can be noted that as x increases, Ea increases

and f0 decreases reflecting a higher barrier between two

wells and an enlargement in potential well respectively. In

the relaxor compound PMN comparing to relaxor com-

pound PMN [27], the difference observed in pre-expo-

nential factor (f0 = 1.72 9 109 Hz) in NN-BTS and PMN

(f0 = 1 9 1012 Hz) can be definitely linked to the shape of

the potential well. Indeed, in the model of double-well

potential, the ion vibrates around its equilibrium position at

the bottom of one of the two wells with a frequency f0. The

narrower the well is, the higher the value of f0 is (large

restoring force). The activation energy Ea, much higher in

our compound, reflects a higher barrier between two wells.

These various features relating to potential well reflect

different mechanisms of polarization. Parameters such as

the anisotropy-related structural type, for example, can

account for the observed differences.

The variations of temperatures TC, Tm, and TVF with com-

position for ceramics of the Na1-xBaxNb1-x(Sn0.5Ti0.5)xO3

system is shown in Fig. 6. It can be noted that the ferro-

electric-relaxor crossover composition (xf-r) is about 0.15.

Then, for x \ xf-r, the paraelectric–ferroelectric transition

temperature decreases as x increases. When the crossover

0

50

100

150

ε'' r

0.5kHz

1 kHz

5 kHz 10 kHz

50 kHz

100 kHz

200 kHz

T(K)

0 100 200 300 400 500

100 200 300 400 500 600

600

1200

1800

2400

3000

3600

4200

100 200 300 400 5000.0000

0.0001

0.0002

0.0003

0.0004

0.0005

0.0006

0.0007

0.0008

1/ ε'r (1 kHz)

Tm= 236K

T0 = 264K

T(K)

Tdév = 370K

T(K)

ε' r 0.5kHz 1 kHz 5 kHz 10 kHz 50 kHz 100 kHz 200 kHz

Fig. 5 Temperature and frequency dependences of er0 and er

00 for

ceramic with composition x = 0.175

Table 1 Parameters Ea (activation energy), TVF (freezing tempera-

ture) and f0 (pre-exponential factor) fitted from the Vogel–Fulcher

equation for ceramics with compositions x = 0.175, x = 0.2, and

x = 0.3 of the Na1-xBaxNb1-x(Sn0.5Ti0.5)xO3 system

x Ea (eV) TVF (K) f0 (Hz)

0.175 0.0098 230 6.66 9 107

0.2 0.0370 167 6.62 9 108

0.3 0.0456 99 1.72 9 109

1946 J Mater Sci (2012) 47:1943–1949

123

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composition is reached, this transition line splits because of

the already mentioned dielectric dispersion in the relaxor

state. For x [ xf-r, the Vogel–Fulcher line TVF(x) is the best

extrapolation of the ferroelectric line TC(x). Similar varia-

tions of TC, Tm, and TVF with composition for ceramics

derived from BaTiO3 were observed by Simon et al. [31].

According to this study, the decrease of TC(x) can be

explained by the decrease of the maximal correlation length

as x increases.

Hysteresis loops

In order to confirm the ferroelectric behavior of these com-

pounds, we have chosen the composition x = 0.1 as an

example. Ferroelectric behavior was characterized using

polarization versus electric field (P–E) hysteresis loops mea-

sured at room temperature. Typical polarization–electric field

(P–E) hysteresis loops of Na1-xBaxNb1-x(Sn0.5Ti0.5)xO3 with

x = 0.1 ceramic was shown in Fig. 7. Non-linear P–E hys-

teresis loops are observed. The remanant polarization Pr is

found to be 5.06 lC cm-2 with a coercive field EC of

3.91 kV cm-1. The shape of hysteresis loop shows clearly a

typical ferroelectric phase and confirms the good densification

of this ceramic.

Piezoelectric measurements

Piezoelectric resonance measurements of the admittance

and the susceptance of the composition x = 0.1 versus

frequency were undertaken with an HP 4194A impedance

analyzer. The main radial electromechanical resonance was

recorded at various temperatures.

Piezoelectric measurements were performed at room

temperature on the ceramic with composition x = 0.1. The

sample (7 mm diameter and 0.8 mm thickness) was first

submitted to a dc filed of about 1.2 kV mm-1 at 300 K

during 5 min in dry helium atmosphere and then short-

circuited for some hours to eliminate any residual space

charge.

The determination of the piezoelectric parameters is

based on the measurements of the real admittance (G) and

imaginary susceptance (B) parts. Figure 8 presents the

variation of the maximal G and B as a function of the

frequency that follows a decrease and disappears around

478 kHz.

The calculation of the piezoelectric parameters, such as

the resonance frequency fr, the anitiresonance frequency,

the mechanic quality factor Qm, parallel frequency of res-

onance, speed of the waves of compression v11, the elec-

tromechanical coupling factor Kp (fine disk), and the

piezoelectric coefficient d31 given in Table 2, were done

with a home-made software following the IEEE [32]

specifications and using the equivalent circuit shown in the

0.10 0.15 0.20 0.25 0.30 0.3550

100

150

200

250

300

350

400

450

500

Tm ( 0.1 kHz) Tm (100 kHz) TVF

Tc

x

T(K

)

Fig. 6 Variations of temperatures TC, Tm, and TVF with composition

for ceramics of the Na1-xBaxNb1-x(Sn0.5Ti0.5)xO3 systemFig. 7 P–E Hysteresis loop measured at room temperature for

Na0.9Ba0.1Nb0.9(Sn0.5Ti0.5)0.1O3 (x = 0.1) ceramic

350000 400000 450000 500000 550000 6000000.00015

0.00020

0.00025

0.00030

0.00035

0.00040

0.00045

0.00050 B(S) G(S)

f(Hz)

B(S

)

0.0001

0.0002

0.0003

0.0004

0.0005

G(S

)

Fig. 8 Admittance G and susceptance B versus frequency for

Na0.9Ba0.1Nb0.9(Sn0.5Ti0.5)0.1O3 (x = 0.1) ceramic around the main

radial piezoelectric resonance, the inset shows schema of the

equivalent circuit for piezoelectric measurement

J Mater Sci (2012) 47:1943–1949 1947

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inset of Fig. 8. This value of the piezoelectric coefficient

(d31 = 42.146 pC N-1) for the composition x = 0.1 can be

considered as important compared with some values

obtained for other ceramics like Na0.5Bi0.5TiO3 (d31 = 14

pC N-1) and Na0.8Li0.2Nb0.8Sb0.2O3 (d31 = 15.3 pC N-1)

[33, 34].

Raman spectroscopy analysis

Raman spectra were recorded using a Labram HR800

monochromator Raman microscope. The Helium laser line

at 633 nm was used for excitation. The spectral resolution

was about 3 cm-1. The experiments were repeated several

times to confirm our results.

Like NN compound, Na0.9Ba0.1Nb0.9(Sn0.5Ti0.5)0.1O3

ceramic is particularly interesting for successive transitions

between different phases. For this reason, we have chosen

this specimen to investigate the phonon spectra related to

these phases observed by dielectric measurements, using

the Raman scattering in heating from 220 to 550 K.

Typical Raman spectra at various temperatures of this

ceramic on heating are shown in Fig. 8. Based on the

published results by Cross [35] and Juang et al. [36] on

LixNa1-xNbO3 compound, the vibrational modes of an

isolated NbO6 octahedron can be decomposed into two

pure bond stretching vibrations of symmetry A1g(m1) and Eg

(m2), two interbond angle bending vibrations m5 and m6 of

symmetry of F2g and F2u, respectively, and two vibrations

m3 and m4, considered as combinations of stretching and

bending, having both F1u symmetry. The high frequency

vibrational mode observed at 601 cm-1 is assigned as m1

stretching. The purposed assignments and the other

observed mode wave numbers are collected in Table 3. As

shown in Fig. 9, the peaks at 275 and 430 cm-1 gradually

decrease in intensity and finally disappear at 383 K. These

peaks can then be considered as the signature of the

orthorhombic to tetragonal phase transition at T2 = 385 K.

Therefore, the peak at 867 cm-1 decreases in intensity and

disappear at 473 K, which confirms the tetragonal to cubic

phase transition at TC = 466 K. This last phase transition

and the rhombohedral to orthorhombic phase transition can

be also observed on the evolution of the full width at half

maximum (FWHM) of the m1 stretching mode in the NbO6

as the temperature increases (Fig. 10).

Conclusion

(1 - x) NaNbO3/xBa(Ti0.5Sn0.5)O3 (x = 0.1) system was

characterized by several techniques and a relationship

between these characterizations was found. XRD analysis

showed that the ceramics with compositions 0 \ x B 0.15

crystallized in tetragonal structure and in cubic one in

the range 0.15 \ x B 0.3. The evolution from a classical

ferroelectric to a relaxor behavior was observed with rising

x. The relaxor ceramics obtained obey the Vogel–Fulcher

law. The ferroelectric and piezoelectric properties for

Table 2 Piezoelectric characteristics of Na0.9Ba0.1Nb0.9(Sn0.5Ti0.5)0.1

O3 (x = 0.1) ceramic at T = 300 K

Radial resonance frequency, fr 478 kHz

Mechanic quality factor, Qm 57.75

Speed of the waves of compression, v11 4515.73 m s-1

Planar coupling factor, Kp 0.128

Piezoelectric coefficient, d31 42.146 pC N-1

Table 3 Wave numbers of Raman band and their assignments for

Na0.9Ba0.1Nb0.9(Sn0.5Ti0.5)0.1O3 and NaNbO3 (refs. [35, 36]) at 300 K

NaNbO3

(Refs. [35, 36])

Na0.9Ba0.1Nb0.9(Sn0.5Ti0.5)0.1O3 Assignments

64 62 Na?

76 Na?

95 105

126

146

157 154 Ba2?

180 m6

186

223 222

258 240 m5

279 275

375

433 430

560

605 601 m1

867

0 200 400 600 800 1000 1200

T = 553K

T = 343K

T = 303K

T = 263KRam

an in

tens

ity

(arb

.uni

ts)

Frequency shifts (cm-1)

T = 223K

T = 513K

T = 473K

T = 433K

T = 383K

Fig. 9 Raman spectra of Na0.9Ba0.1Nb0.9(Sn0.5Ti0.5)0.1O3 compound

at different temperatures

1948 J Mater Sci (2012) 47:1943–1949

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x = 0.1 ceramic were studied. The polarization hysteresis

loops were observed with a remanant polarization of

5.06 lC cm-2. The evolution of the Raman spectra for

x = 0.1 at different temperatures confirms our structural

and dielectrics results. Some of these new compositions are

of interest for applications thanks to their physical prop-

erties and environmentally friendly character.

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200 240 280 320 360 400 440 480 520 560 60075

90

105

120

TC = 466 K

T1 =384 K

Fre

quen

cy (

cm-1

)

T (K)

FWHM

T2 =254 K

Fig. 10 Temperature dependence of the full width at half maximum

(FWHM) of the m1 stretching mode in the NbO6 of Na0.9Ba0.1Nb0.9

(Sn0.5Ti0.5)0.1O3 ceramic

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