Effect of Ba(Zn1/3Ta2/3)O3 and SiO2 ceramic fillerson the microwave dielectric properties of butyl rubber composites

J. Chameswary • M. T. Sebastian

Received: 22 May 2013 / Accepted: 23 July 2013 / Published online: 2 August 2013

� Springer Science+Business Media New York 2013

Abstract Butyl rubber–Ba(Zn1/3Ta2/3)O3 (BR–BZT)

composites and butyl rubber–silica (BRS) composites were

prepared by sigma mixing. The dielectric properties at

1 MHz and 5 GHz of BR–BZT and BRS composites were

investigated as a function of ceramic loading and were

found to be improved with filler loading. For a optimum

BZT loading of 0.26 vf, the BR–BZT composite have

er = 4.88, tand = 0.0022 (at 5 GHz), coefficient of ther-

mal expansion (CTE) = 112 ppm/�C, thermal conductivity

(TC) = 0.30 Wm-1 K-1 and water absorption = 0.047

vol%. The BRS composites attained er = 2.79, tand =

0.0039 (at 5 GHz), CTE = 102 ppm/�C, TC = 0.40

Wm-1 K-1 and water absorption = 0.078 vol% for the

same loading of silica. The stress–strain curves of both

composites showed good flexibility of the composite. The

measured relative permittivity and TC of both composites

were compared with different theoretical approaches.

1 Introduction

Flexible electronics is a current research area in the

microelectronic industry. Flexible electronics known as

flex circuits is a technology for building electronic circuits

by depositing electronic devices on flexible substrates [1].

A new generation of flexible circuit connectors could

produce a new class of electronic applications, such as

stretchable thermometers, biomedical devices and elec-

tronic clothing etc. [2]. The future of electronic appliances

should be flexible and stretchable in order to meet the

demand of today’s electronic industry [3]. The need for

stretchability for electronic components is reported in the

annual report of advanced packaging and interconnection

[4]. Today’s citizen carries more electronic systems near or

even inside the body. Hence the systems must be light

weight, must take the desirable shape of the object and

should follow all complex movements of these objects [4].

The ever increasing demand for high performance elec-

tronic devices needs new materials to be used as circuit

board laminates.

Extensive research is being done in the field of microwave

dielectric properties of low permittivity filler–polymer

composites [5–8]. Recently Manu et al. [9] reported the

effect of Ba(Zn1/3Ta2/3)O3 ceramic on dielectric, mechanical

and thermal properties of high density polyethylene com-

posites. Nijesh et al. [10] reported that PTFE filled with 76

wt% Ba(Mg1/3Ta2/3)O3 ceramic attained a relative permit-

tivity of 6.7 and a loss tangent of 0.003 in the X-band. Kim

and Chang [11] investigated the effect of ZnNb2O6 and

crystallinity of polymers on dielectric properties of

ZnNb2O6/polytetrafluoroethylene, polypropylene and poly-

styrene composites at 10–16 GHz. Silica loaded polymer

composites were also reported for microwave electronic

applications [12–14]. These polymer-ceramic composites

are not useful for stretchable electronic applications.

Low loss and low permittivity composites are needed for

electronic packaging applications. Recently elastomer

ceramic composites have been found to be most promising

candidates for flexible electronic applications. These

composite combines the stretchability and light weight of

elastomer with good dielectric and thermal properties of

ceramics. Namitha et al. [15] recently studied the effect of

micron and nano alumina on microwave dielectric, thermal

and mechanical properties of silicone rubber composites

J. Chameswary � M. T. Sebastian (&)

Materials Science and Technology Division, National Institute

for Interdisciplinary Science and Technology (CSIR),

Trivandrum 695019, India

e-mail: mailadils@yahoo.com

123

J Mater Sci: Mater Electron (2013) 24:4351–4360

DOI 10.1007/s10854-013-1410-0

and silicone rubber-micron alumina composite is found to

be good for microwave substrate applications. Tomer and

Randall [16] investigated the electrical properties of sili-

cone elastomer–BaTiO3 composites as a function of cera-

mic volume fraction (vf) and connectivity at 1 kHz.

Recently microwave dielectric properties of butyl rubber

(BR) based composites are reported by Sebastian et al.

[17–20]. Elastomer–silica composites are reported in order

to improve the dielectric and mechanical properties of

elastomer [21, 22]. Hanna et al. [21] reported the dielectric

properties of styrene–butadiene rubber–silica composites in

the frequency range from 60 to 108 Hz. Ward et al. [22]

investigated the effect of stress strain cycles on the

dielectric properties of BR vulcanizates filled with silica in

the frequency range 10-3–106 Hz.

The microwave dielectric properties of BR–BZT and BR–

silica (BRS) composites were not yet reported. In the present

work, we try to make an insight into the effect of BZT and

silica ceramic on the microwave dielectric, thermal and

mechanical properties of BR composites as a function of

ceramic volume fraction. BR is a synthetic elastomer with

excellent dielectric properties in the microwave frequencies

(er = 2.4, tand & 10-3), good mechanical flexibility, age-

ing resistance, weathering resistance etc. [23]. BZT is a good

dielectric ceramic with er = 30 and tand & 10-3 [24] and

silica is another well known ceramic with excellent dielectric

properties (er = 4, tand & 10-3), good thermal properties

etc. In the present paper we report the use of BZT and silica

ceramic fillers to improve the dielectric, thermal and

mechanical properties of BR.

2 Experimental

Ba(Zn1/3Ta2/3)O3 ceramic was prepared by following the

conventional solid state ceramic route. Stoichiometric

quantities of BaCO3, ZnO (99.9? %, Sigma-Aldrich) and

Ta2O5 (99.99 %, Treibacher Industries,) were ball milled for

24 h in distilled water using yttria-stabilized zirconia balls in

a plastic container. The slurry was dried and calcined at

1,200 �C for 4 h. The calcined powder was ground well and

sintered at 1,500 �C for 4 h. The powder was then sieved

through a 25 lm sieve. Silica was procured from Sigma

Aldrich and was dried at 100 �C for 24 h before use. BR–

Ba(Zn1/3Ta2/3)O3 and BRS composites were prepared by

sigma mixing as described in our earlier paper [25]. The

density of BZT (q & 7.96 g cm-3) is higher than that of

silica (q & 2.6 g cm-3). Hence the BR–BZT composites

were prepared up to a filler loading of 400 phr and that of

silica filled composites up to a loading of 200 phr. The

sample designation and the corresponding ceramic volume

fraction are given in Table 1. The composites were then hot

pressed at 200 �C for 90 min under a pressure of 2 MPa.

The phase purity of the ceramic powder was analyzed by

X-ray powder diffraction technique with Cu–Ka radiation

(Philips X’Pert PRO MPD X-ray diffractometer). The

microstructures of the composites were examined using a

scanning electron microscope (SEM) (Jeol Model, JSM

5600LV). The dielectric properties at 1 MHz were mea-

sured following the parallel plate capacitor method using a

LCR meter (Hioki Model, 3532-50). The microwave

dielectric properties were measured using a split post

dielectric resonator (SPDR) with the help of a vector net-

work analyzer (Agilent Technologies, E5071C, ENA Ser-

ies) [26]. The microwave dielectric properties of both

composites were also investigated after bending the sam-

ples manually by an angle of 180� and the bending cycle

was repeated for 125 times. The moisture absorption

characteristics of the composites were measured following

ASTM D 570-98 procedure [19] using the samples with

dimensions 50 mm 9 50 mm 9 2 mm. The samples were

weighed accurately and immersed in distilled water for

Table 1 Dielectric and water

absorption properties of BR–

BZT and BRS composites

a Parts/100b The corresponding ceramic

volume fraction is given in

parenthesis

Composite

material

Sample

designation

Amount of filler

(Phr)a ()ber

(1 MHz)

tand(1 MHz)

Water absorption

(vol%)

BR–BZT BR-0 0 (0) 2.44 0.0003 0.039

BR–BZT-1 10 (0.01) 2.45 0.0010 0.040

BR–BZT-2 25 (0.028) 2.50 0.0012 0.041

BR–BZT-3 50 (0.055) 2.71 0.0015 0.043

BR–BZT-4 100 (0.10) 3.11 0.0016 0.044

BR–BZT-5 200 (0.19) 3.49 0.0018 0.045

BR–BZT-6 300 (0.26) 4.45 0.0019 0.047

BR–BZT-7 400 (0.32) 5.46 0.0021 0.057

BRS BRS-1 10 (0.03) 2.51 0.002 0.048

BRS-2 25 (0.08) 2.75 0.005 0.052

BRS-3 50 (0.15) 2.83 0.006 0.059

BRS-4 100 (0.26) 3.10 0.008 0.078

BRS-5 200 (0.42) 3.37 0.010 0.091

4352 J Mater Sci: Mater Electron (2013) 24:4351–4360

123

24 h. The samples were then taken out and again weighed

after removing the excess water from the surface. The

vol% of water absorption was then calculated using the

relation,

Volume% water absorption ¼ ðWf �WiÞ=qw

Wf �Wi

qwþWi=qc

� 100

ð1Þ

where Wi and Wf are the initial and final weights of the

sample and qw and qc are the densities of distilled water

and sample respectively.

The thermal conductivity (TC) of the composites was

measured by laser flash technique using a TC analyzer

(Flash LineTM 2000, Anter Corporation, USA) by using

the relation

TC ¼ k� Cp � q ð2Þ

where k is the thermal diffusivity, Cp is the specific heat

capacity at room temperature and q is the density of the

sample.

The linear coefficient of thermal expansion (CTE) of

each composite was measured using a dilatometer (Netzsch

Model, DIL 402 PC) in the temperature range from 30 to

100 �C. Tensile tests of both BR–BZT and BRS compos-

ites were carried out in a Universal Testing Machine

(Hounsfield Model, H5K-S UTM) with a rate of grip sep-

aration of 500 mm/min.

3 Results and discussion

Figure 1 shows the XRD pattern of sintered BZT and sil-

ica. The peaks were indexed based on the JCPDS file no.

18-0201 and 89-8934 for BZT and silica respectively. The

phase purity of both the ceramics were obvious from the

XRD patterns.

Figure 2a, b shows the SEM images of silica and BZT

powder respectively. Both silica and BZT particles are

irregularly shaped and are \1 lm in size. The Fig. 2c, d

represents fractured SEM images of BRS-5 and BR–BZT-7

respectively. From the figure it is clear that the filler par-

ticles are uniformly distributed in the rubber matrix of both

composites.

Table 1 shows the dielectric and water absorption

properties of BR–BZT and BRS composites. The relative

permittivity and loss tangent of both the composites

increases with filler content. The increase in er of the

composites is mainly due to the high relative permittivity

of BZT and silica as compared to rubber matrix. The

connectivity among the filler particles increases at higher

filler content which in turn increases the relative

permittivity of the composites [27]. The loss tangent which

is the main factor affecting the frequency selectivity of a

material is influenced by many factors such as porosity,

microstructure and defects [28]. The interfacial area and

the possibility of accumulation of space charges at inter-

face of polymer–ceramic composite increases with increase

in the ceramic loading which in turn increases the dielectric

loss. The tand of BRS composite is found to be higher than

that of BR–BZT composites. This may be due to the

presence of more moisture content in the silica sample.

Hanna et al. [21] reported a similar observation in SBR–

SiO2 composites. The moisture content is an important

parameter for materials used for packaging applications.

Absorption of moisture from the working atmosphere will

degrade especially the dielectric properties since the water

is a polar molecule. It is also evident from the Table 1 that

the vol% of moisture content increases with filler content

for both BR–BZT and BRS composites. This may be due to

the hydrophilic nature of ceramic. It has been reported that

Fig. 1 The XRD pattern of a Ba(Zn1/3Ta2/3)O3 and b SiO2

J Mater Sci: Mater Electron (2013) 24:4351–4360 4353

123

materials with moisture absorption up to about 0.1 % can

be used for electronic packaging applications [29]. The

present composites exhibit moisture absorption within this

limit.

Figure 3a, b depicts the microwave dielectric properties

of BR–BZT and BRS composites at 5 GHz. The relative

permittivity of both the composites increases with filler

loading. The increased total polarizability of composite

material contributes to the increase in relative permittivity

of the composites. The relative permittivity of BZT filled

BR composites has er of 5.72 for the maximum filler

loading of 0.32 vf. The relative permittivity of BRS com-

posite is 3.09 for the maximum silica loading of 0.42 vf.

The BZT based composite has higher relative permittivity

since silica has a lower relative permittivity. From the

figure it is also clear that the dielectric loss of BR–BZT and

BRS composites shows similar trend as that of relative

permittivity with increase in filler loading. The tand of BR–

BZT composites is lower than that of silica filled com-

posites. The tand of BR–BZT-7 and BRS-5 composites at

5 GHz is 0.0025 and 0.0045 respectively. The increase in

loss of BRS composites is due to the presence of more

moisture content in silica composites than that of BR–BZT

composites which is evident from Table 1. The dipole

relaxation of water molecule in the microwave frequency

contributes to dielectric loss [30].

The precise prediction of effective relative permittivity of

the composites is very important for electronic packaging

applications. Figure 4a, b shows the comparison of experi-

mental and theoretical relative permittivity of the BR–BZT

and BRS composites at 5 GHz respectively. In the present

study, the following equations were used to predict the rel-

ative permittivity of both the composites [31].

Fig. 2 SEM image of a SiO2 powder, b Ba(Zn1/3Ta2/3)O3 powder, c fractured surface of BRS-5 and d BR–BZT-7

Fig. 3 Variation of er and tand of a BR–BZT and b BRS composites

with filler content at 5 GHz

4354 J Mater Sci: Mater Electron (2013) 24:4351–4360

123

Lichtenecker equation:

ln eeff ¼ ð1� vf Þ ln em þ vf ln ef ð3Þ

Maxwell–Garnet equation:

eeff ¼ em

2em þ ef þ 2vf ef � em

� �

2em þ ef � vf ef � em

� � ð4Þ

Jayasundere–Smith equation:

eeff ¼em 1� vf

� �þ ef vf

3em

eiþ2em

h i1þ 3vf ef�emð Þ

eiþ2em

� �� �

1� vf þ vf3em

efþ2em

h i1þ 3vf ef�emð Þ

efþ2em

� �� � ð5Þ

Effective medium theory (EMT):

eeff ¼ em 1þvf ef � em

� �

em þ n 1� vf

� �ef � em

� �

" #

ð6Þ

where eeff, ef, em are the relative permittivity of the com-

posites, filler and matrix respectively and vf is the volume

fraction of the filler.

It is clear from Fig. 4a that the Maxwell–Garnet equa-

tion shows considerable deviation from the experimental

values and Lichnetecker equation is valid up to a volume

fraction of 0.19 and shows deviation at higher BZT load-

ing. This may be due to the lack of consideration of

interfacial interaction between the polymer and the filler

particles. The Jaysundere Smith equation is in agreement

with experimental data since this equation considers the

interactions between the fields of neighbouring filler par-

ticles [32]. The experimental relative permittivity is very

well fit with EMT model proposed by Rao et al. [33]. This

model includes a ceramic morphology factor ‘n’ which is

determined empirically. The value of n for BR–BZT

composite is 0.2. From Fig. 4b it is clear that the experi-

mental relative permittivity of BRS composites are in

agreement with theoretical models up to a filler loading of

0.15 vf and shows deviation at higher silica content. The

shape factor, n for BRS composites is also 0.2. The

effective permittivity of a composite depends on the vari-

ous factors such as relative permittivity of individual

components in the system, their volume fractions, shape,

size, porosity, interphase polarizability, and interphase

volume fractions. All these parameters cannot be accounted

in a single equation. Hence the experimental results show

deviation from the theoretical values at higher filler

content.

The bending effect on dielectric properties is important

as far as stretchable electronic applications concerned. The

effects of bending on microwave dielectric properties of

BR–BZT and BRS composites are shown in Figs. 5 and 6

respectively. It is evident from the Fig. 5a, b that the rel-

ative permittivity of the composites is independent of

repeated bending. In the case of BRS composites, the er

shows a slight decrease after a bending cycle of 75 for BR

loaded with 0.42 vf of silica content. This may be due to the

aggregating tendency of silica at higher loading. From

Fig. 6a, b it is clear that the loss tangent of the BR–BZT

composites shows a small variation with repeated bending.

But the variation is only marginal. The tand of silica filled

composites shows a slight decrease after 75 cycles of

bending [34].

Figure 7a, b shows the variation of relative permittivity

of BR–BZT and BRS composites with temperature at

1 MHz. It is noted that the variation in relative permit-

tivity with temperature is small and the relative permit-

tivity of both the composites decreases with temperature.

The polarizability of dipoles decreases with increase in

temperature which decreases the relative permittivity of

the composites [35]. Both BR–BZT and BRS composites

are almost thermally stable in the measured temperature

range.

Heat dissipation from integrated circuits is a crucial

problem for electronic industry. The TC of polymers is

Fig. 4 Comparison of theoretical and experimental relative permit-

tivity of a BR–BZT and b BRS composites at 5 GHz

J Mater Sci: Mater Electron (2013) 24:4351–4360 4355

123

very low, ranging from 0.14 to 0.60 Wm-1 K-1 [36] and

can be improved by addition of ceramic fillers as the TC

of ceramic is higher than that of polymers. The TC of the

composites depends on the intrinsic conductivities of filler

and matrix, shape and size of the filler, and the loading

level of filler [37]. The variation of TC of BR–BZT and

BRS composites with filler content are shown in Fig. 8.

The TC of BR is 0.13 Wm-1 K-1. As the TC of fillers

BZT (3.9) and silica (1.4) are higher than that of matrix

the TC of both BR–BZT and BRS composites increased

with filler content. The increase in TC of both the

composites at higher filler content is due to the presence

of more connecting paths between the filler particles

[38]. The TC of BR–BZT composites increases from 0.13

to 0.35 as the filler loading increases from 0 to 0.32

vf and that of BRS composites from 0.13 to 0.56 as

the silica loading increases from 0 to 0.42 vf. The TC

of the composite can be further enhanced by adding

high TC fillers such as aluminium nitride, silicon nitride

etc.

Several theoretical models or equations have been

reported [39, 40] for predicting the TC of composites. In

the present study, following models are used to predict the

TC of the composites:

Fig. 5 Variation of relative permittivity of a BR–BZT and b BRS

composites with bending

Fig. 6 Variation of loss tangent of a BR–BZT and b BRS composites

with bending

Fig. 7 The temperature dependence of relative permittivity of a BR–

BZT and b BRS composites at 1 MHz

4356 J Mater Sci: Mater Electron (2013) 24:4351–4360

123

Geometric mean model:

kc ¼ kvf

f k1�vf

m ð7Þ

Maxwell–Eucken model:

kc ¼ km

kf þ 2km þ 2vf ðkf � kmÞkf þ 2km � vf ðkf � kmÞ

� �ð8Þ

Cheng–Vachon model:

1

kc

¼ 1ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiCðkm � kf Þ km þ Bðkf � kmÞ

q

ln

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffikm þ Bðkf � kmÞ q

þ B2

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiCðkm � kf Þ

p

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffikm þ Bðkf � kmÞ q

� B2

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiCðkm � kf Þ

p þ 1� B

km

ð9Þ

where

B ¼ffiffiffiffiffiffiffiffiffiffi3vf�2

q; C ¼ �4

ffiffiffiffiffiffiffiffiffiffi2�3vf

q

Nielson model:

kc ¼ km

1þ ABvf

1� Bvf w

� �

B ¼kf

km� 1

kf

kmþ A

where w ¼ 1þ 1� vfm

v2fm

!

vf

ð10Þ

A(-3) is a function of geometry of the filler particles

and vfm is the maximum filler content.

Where kc, km, and kf are the thermal conductivities of the

composite, matrix, and filler, respectively, and vf is the

volume fraction of the filler.

Figure 9a compares the experimental and calculated TC

of BR–BZT composites. It is worth to be noted that the

Geometric mean model and Cheng-Vachon model is in

good agreement with experimental values. Cheng and

Vachon assumed a parabolic distribution of the discontin-

uous phase in the continuous phase based on Tsao’s model

[41]. The constants of this parabolic distribution were

determined by analysis and presented as a function of the

discontinuous phase volume fraction. Maxwell–Eucken

model considers the composite system as randomly dis-

tributed and non interacting homogeneous spheres in a

homogeneous medium which shows slight deviation from

experimental values. The Nielson model considers the

composite as a homogeneous system with an ideal inter-

face. However, with the increase in the volume fraction of

the filler, the mismatch between the matrix and the filler in

the form of interfacial gap becomes more serious which

adversely affects the heat conduction. Hence the predicted

values of Nielson model show very large deviation beyond

filler loading of 0.19 vf of BZT. From Fig. 9b it is evident

that all the theoretical models match with measured TC of

BRS composites at lower silica loading and deviates from

Fig. 8 The variation of thermal conductivity of BR–BZT and BRS

composites with ceramic loading

Fig. 9 Comparison of theoretical and experimental thermal conduc-

tivity of a BR–BZT and b BRS composites with filler loading

J Mater Sci: Mater Electron (2013) 24:4351–4360 4357

123

predicted values after a filler loading of 0.15 vf. The wide

variations in filler geometry, orientation and dispersion

makes it difficult to compare composites filled with dif-

ferent materials. Moreover, the interfacial boundary ther-

mal resistance between the filler particles and the matrix,

referred to as Kapitza resistance, [42] is not taken into

account while calculating the TC of composites. It is not

possible to measure it at the molecular level where it takes

place. As a result, experimental and theoretical TC data are

often not in agreement.

Figure 10a, b shows the variation of specific heat

capacity and thermal diffusivity of BR–BZT and BRS

composites with filler loading respectively. Both the

composites shows similar trend of variation with ceramic

content. The thermal diffusivity of both the composites

increases with ceramic loading. The specific heat capacity

of composites decreases with filler volume fraction. This

may be due to the low Cp value of BZT and silica. A

similar observation was reported by Subodh et al. [43] in

PTFE–Sr2Ce2Ti5O16 composites and Aravind et al. [44] in

lead titanate/polyvinylidene fluoride composites.

The variation of CTE of BR composites filled with BZT

and silica are shown in Fig. 11. It is seen that the CTE of BR–

BZT and BRS composites decreases with filler loading as

the CTE of the fillers, BZT (4.2 ppm/�C) and silica

(0.5 ppm/�C) are lower than that of rubber matrix (191 ppm/

�C). The interfacial properties of the filler significantly affect

the CTE of the composites. The thermal expansion of com-

posites is more reduced in strong interfacial system than that

of poor interface system [45]. Recently Goyal et al. [46]

reported that the unconstrained polymer chains become

constrained upon the addition of ceramic which reduces the

thermal expansion of composites.

Figure 12 shows the stress–strain curves of BR-0, BR–

BZT-7 and BRS-5. The stress needed for elongation

increases with filler content. The interfacial adhesion plays

a major role in mechanical properties of the composites.

Todorova et al. [47] reported that the interfacial adhesion

increases with filler loading which inturn increases the

effectiveness of the stress transfer from rubber chains.

Salaeh et al. [48] reported that the mobility of molecular

Fig. 10 Variation of thermal diffusivity and specific heat capacity of

a BR–BZT and b BRS composites with ceramic loading

Fig. 11 Variation of coefficient of thermal expansion of BR–BZT

and BRS composites with ceramic loading Fig. 12 Stress–strain curves of BR–BZT and BRS composites

4358 J Mater Sci: Mater Electron (2013) 24:4351–4360

123

chains decreases due to the incorporation of ceramic par-

ticles and hence the increase in stiffness of the composite.

From the figure it is clear that the silica filled composite

shows higher reinforcement than that of BZT filled com-

posite. Silica is reported to be good reinforcing filler for

rubber composites [49, 50].

4 Conclusions

The BR–BZT and BRS composites were prepared and the

effect of ceramic loading on dielectric, thermal and

mechanical properties was investigated. The dielectric

properties of the composites were investigated at 1 MHz

and 5 GHz and were improved with ceramic loading. The

CTE and TC of both BR–BZT and BRS composites were

also improved with filler addition. The experimental rela-

tive permittivity and TC of the both composites were

compared with theoretical models. The mechanical prop-

erties show the flexibility of both composites. The BR–

BZT composite have er = 4.88, tand = 0.0022 (at 5 GHz),

CTE = 112 ppm/�C, TC = 0.30 Wm-1 K-1 and water

absorption = 0.047 vol% for a optimum BZT loading of

0.26 vf. The BRS composites attained er = 2.79, tand =

0.0039 (at 5 GHz), CTE = 102 ppm/�C, TC = 0.40

Wm-1 K-1 and water absorption = 0.078 vol% for a

optimum silica loading of 0.26 vf. The loss tangent and

moisture absorption values of BR–BZT composites are

superior to that of BRS composites. Hence the BZT filled

BR composites are suitable candidate for microwave sub-

strate applications.

Acknowledgments The authors are grateful to the Council of Sci-

entific and Industrial Research (CSIR), India for the award of Senior

Research Fellowship. The authors are thankful to Dr. P. Prabhakar

Rao and Mr. M. R. Chandran for SEM, and Mr. Brahmakumar for

tensile measurements.

References

1. B. Erik, W. William, Z. Lisong, J. Tom, T. Greg, A. B. D. Rod,

B. David, V. Nikhil, C. Robert, in Material Research Society.

Flexible Electronics Symposium, San Francisco, CA (2004)

2. D. Lucian, Science Nano-Biotechnology, July 11th (2007)

3. J. Provoost, IMEC www.Onboard-Technology.com 8–9. (2008)

4. in Flexible and Stretchable Electronics. Annual Report of

Advanced Packaging and Interconnection (2011)

5. S. George, V.N. Deepu, P. Mohanan, M.T. Sebastian, Polym.

Eng. Sci. 50, 570 (2010)

6. P.S. Anjana, V. Deepu, S. Uma, P. Mohanan, J. Philip, M.T.

Sebastian, J. Polym. Sci. Part B: Polym. Phys. 48, 998 (2010)

7. T. Joseph, S. Uma, J. Philip, M.T. Sebastian, J. Mater. Sci.:

Mater. Electron. 23, 1243 (2012)

8. K.P. Murali, S. Rajesh, O. Prakash, A.R. Kulkarni, R. Ratheesh,

Mater. Chem. Phys. 113, 290 (2009)

9. K.M. Manu, S. Soni, V.R.K. Murthy, M.T. Sebastian, J. Mater.

Sci.: Mater. Electron. (2013). doi:10.1007/s10854-013-1064-y

10. K.J. Nijesh, J.K. Stanly, K.P. Murali, R. Ratheesh, Mater. Chem.

Phys. 122, 507 (2010)

11. E.S. Kim, J.J. Chang, IEEE Trans. Ultrason. Ferroelectr. Freq.

Control 58, 1939 (2011)

12. K.P. Murali, S. Rajesh, O. Prakash, A.R. Kulkarni, R. Ratheesh,

Compos. A 40, 1179 (2009)

13. M.G. Todd, F.G. Shi, Microelectron. J. 33, 627 (2002)

14. H. Couderc, I. Preda, M. Frechette, S. Savoie, M. Reading, A.

S. Vaughan, J. Castellon, in Annual Report Conference on

Electrical Insulation and Dielectric Phenomena (CEIDP), p. 511

(2012)

15. L. K. Namitha, J. Chameswary, S. Ananthakumar, M. T. Sebas-

tian, Ceram. Int. doi:10.1016/j.ceramint.2013.02.047 (2013)

16. V. Tomer, C.A. Randall, J. Appl. Phys. 104, 074106-1 (2008)

17. J. Chameswary, L.K. Namitha, M. Brahmakumar, M.T. Sebas-

tian, Int. J. Appl. Ceram. Technol. (2013). doi:10.1111/ijac.12067

18. J. Chameswary, M.T. Sebastian, Ceram. Int. 39, 2795 (2013)

19. C. Janardhanan, D. Thomas, G. Subodh, S. Harshan, J. Philip,

M.T. Sebastian, J. Appl. Polym. Sci. 124, 3426 (2012)

20. D. Thomas, C. Janardhanan, M.T. Sebastian, Int. J. Appl. Ceram.

Technol. 8, 1099 (2011)

21. F.F. Hanna, A.A. Yehiab, A.F. Abou-Bakr, Brit. Polym. J. 5, 83

(1973)

22. A.A. Ward, B. Stoll, W. Soden, S. Herminghaus, A.M. Bishai,

F.F. Hanna, J. Macromol. Sci. Phys. B42, 1265 (2003)

23. I.K. Hakim, A.M. Bishai, A.L. Saad, J. Appl. Polym. Sci. 35,

1123 (1988)

24. S. Kawashima, M. Nishida, I. Ueda, H. Ouchi, J. Am. Ceram.

Soc. 66, 421 (1983)

25. H. Barron, Modern Synthetic Rubbers (Chapman & Hall, London,

1949)

26. M.T. Sebastian, Dielectric Materials for Wireless Communica-

tions, 1st edn. (Elsevier, Oxford, 2008)

27. S.M. David, M. Blaszkiewicz, R.E. Newnham, J. Am. Ceram.

Soc. 73, 2187 (1990)

28. N.G. Devaraju, E.S. Kim, B.I. Lee, Microelectron. Eng. 82, 71

(2005)

29. T.S. Laverghetta, Microwave Materials and Fabrication Tech-

niques (Artech House, Dedham, 1985)

30. F. Xiang, H. Wang, X. Yao, J. Eur. Ceram. Soc. 26, 1999 (2006)

31. M.T. Sebastian, H. Jantunen, Int. J. Appl. Ceram. Technol. 7, 415

(2010)

32. N. Jayasundere, B.V. Smith, J. Appl. Phys. 73, 2462 (1993)

33. Y. Rao, J. Qu, T. Marinis, C.P. Wong, IEEE Trans. Compon.

Packag. Technol. 23, 680 (2000)

34. A.A.M. Ward, B. Stoll, W.V. Soden, S. Herminghaus, A.A.

Mansour, Macromol. Mater. Eng. 278, 971 (2003)

35. L.L. Hench, J.K. West, Principles of Electronic Ceramics (Wiley,

New York, 1990)

36. I.H. Tavman, Int. Commun. Heat Mass 25, 723 (1998)

37. S. Kemaloglu, G. Ozkoc, A. Aytac, Thermochim. Acta 499, 40

(2010)

38. H. He, R. Fu, Y. Shen, Y. Han, X. Song, Compos. Sci. Technol.

67, 2493 (2007)

39. R.C. Progelhof, J.L. Throne, R.R. Ruetsch, Polym. Eng. Sci. 16,

615 (1976)

40. J.K. Carson, S.J. Lovatt, D.J. Tanner, A.C. Cleland, J. Food Eng.

75, 297 (2006)

41. G.T.N. Tsao, Ind. Eng. Chem. 53, 395 (1961)

42. J.C. Maxwell, A Treatise on Electricity and Magnetism (Dover,

New York, 1954)

43. G. Subodh, M.V. Manjusha, J. Philip, M.T. Sebastian, J. Appl.

Polym. Sci. 108, 1716 (2008)

J Mater Sci: Mater Electron (2013) 24:4351–4360 4359

123

44. M. Aravind, C.W. Ong, H.L.W. Chan, Polym. Compos. 23, 925

(2002)

45. T.H. Ho, C.S. Wang, J. Appl. Polym. Sci. 51, 2047 (1994)

46. R.K. Goyal, A.N. Tiwari, Y.S. Negi, Compos. B 47, 70 (2013)

47. Z. Todorova, N. Dishovsky, R. Dimitrov, F.E. Tantawy, A.N.

Aal, A. Al-Hajry, M. Bououdina, Polym. Compos. 29, 109 (2008)

48. S. Salaeh, N. Muensit, P. Bomlai, C. Nakason, J. Mater. Sci. 46,

1723 (2011)

49. N. Rattanasoma, T. Saowaparkc, C. Deeprasertkul, Polym. Test.

26, 369 (2007)

50. K. Boonkerd, S. Chuayjuljit, D. Abdulraman, W. Jaranrangsup,

Rubber Chem. Technol. 85, 1 (2012)

4360 J Mater Sci: Mater Electron (2013) 24:4351–4360

123