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Home / Issues / № 2, 2014

Engineering

High piezoelectric performance of novel 1–3-type lead-free composites
Topolov V.Yu., Bowen C.R.

The present report is devoted to the piezoelectric response of the 1–3 single crystal (SC) / polymer composite. As is known, the most commonly chosen as a piezoelectric component are the perovskite-type ferroelectric ceramics or relaxor-ferroelectric SCs [1], and the overwhelming majority of these components are lead-based materials. A new way of improving the effective electromechanical properties and applicability of piezoelectric composites may be concerned with use of a lead-free component with considerable piezoelectric activity. Recent studies [2] suggest that good candidates for composite components are SCs of ferroelectric niobate solid solutions, e.g.  [Lix(K0.501Na0.499)1-x](Nb0.660Ta0.340)O3 (KNN-TL) and (K0.562Na0.438)(Nb0.768Ta0.232)O3 (KNN-T) with a large piezoelectric coefficient g33 that describes a piezoelectric sensitivity. The aim of our study is to show a performance of novel composites based on either KNN-TL or KNN-T SCs.    

A prediction of effective electromechanical properties of the 1–3 SC / polymer composite with parallelepiped-shaped long SC rods (Fig. 1) enables us to analyse the piezoelectric coefficients and related parameters at volume fractions of the SC component 0< m< 1. In connection with the large g33 value of the SC [2] we emphasise the piezoelectric coefficient  and its hydrostatic analogue  = ++, squared figures of merit ()2 =  and ()2 = , and hydrostatic electromechanical coupling factor  (Table 1), where  is the piezoelectric coefficient, and  = ++ is its hydrostatic analogue. The polymer is piezo-passive with either a positive Poisson’s ratio (polyurethane) or a negative one (auxetic polyethylene). While max and max are located at small volume fractions (0< m < 0.025) irrespective of polymer, we show data at

Fig. 1. Schematic of the 1–3 SC / polymer composite. (X1X2X3) is the rectangular co-ordinate system. m and 1 – m are volume fractions of SC and polymer, respectively, x, y and z are main crystallographic axes of SC. The spontaneous polarisation vector of the SC rod Ps(1) is shown with the arrow. The SC rods with square bases are regularly distributed in the polymer matrix, and centres of symmetry of the bases form a simple square lattice in the (X1OX2) plane. Electrodes are to be applied parallel to the (X1OX2) plane.

Table 1. Effective parameters of the 1–3 SC / polymer composite (0.05£ m£ 0.15) and SCs (m= 1)

SC

Polymer

m

,

mV.m/N

,

mV.m/N

()2,

10-12 Pa-1

()2,

10-12 Pa-1

KNN-TL

Polyurethane

0.05

627

142

97.9

5.03

0.135

 

 

0.10

400

87.7

88.5

4.25

0.129

 

 

0.15

291

61.3

74.7

3.32

0.118

 

Auxetic

0.05

888

1830

256

1080

0.439

 

polyethylene

0.10

473

835

148

461

0.342

 

 

0.15

322

496

104

247

0.280

 

---

1

50.6

4.01

17.9

112

0.116

KNN-T

Polyurethane

0.05

839

188

78.7

3.93

0.120

 

 

0.10

546

117

65.8

3.03

0.110

 

 

0.15

397

81.3

52.9

2.22

0.0972

 

Auxetic

0.05

1130

2310

162

677

0.372

 

polyethylene

0.10

622

1080

93.7

289

0.282

 

 

0.15

429

656

66.0

154

0.227

 

---

1

68.6

3.39

11.1

27.1

0.0571

N o t e s. 1. Room-temperature electromechanical constants of SCs and polymers were taken from Ref. 2 and Ref. 3, respectively. 2. The matrix method [1] was applied to calculate the full set of effective electromechanical constants of the 1–3 composite.

m³ 0.05 to follow a manufacturing tolerance. Relatively small volume fractions of SC m do not lead to a significant decrease of the effective parameters (Table 1). The use of an auxetic polyethylene leads to larger values of all of the effective parameters listed in Table 1, and the hydrostatic response and electromechanical coupling become stronger because of > 0 and > 0: this peculiarity is due to positive elastic compliances of the polymer component. The data from Table 1 show that, in the case of the auxetic polymer, the effective parameters of the composite are much more than those related to a conventional 1–3 PZT ceramic / polymer composite [1, 3]. The lead-free 1–3 composites considered above can be suitable for piezoelectric sensor (large ), hydroacoustic (large , ()2 and ) and energy-harvesting applications (large ()2 and ).

The research subject is concerned with the Programme Supporting the Research at the Southern Federal University (Russia). Prof. Dr. C.R. Bowen acknowledges funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement no. 320963 on Novel Energy Materials, Engineering Science and Integrated Systems (NEMESIS).



References:
1. V.Yu. Topolov and C.R. Bowen, Electromechanical Properties in Composites Based on Ferroelectrics. London: Springer, 2009.

2. X. Huo, L. Zheng, R. Zhang et al., CrystEngComm, 2014, DOI:10.1039/C4CE01208A (in press).

3. V.Yu. Topolov, P. Bisegna and C.R. Bowen, Piezo-active Composites. Orientation Effects and Anisotropy Factors. Berlin, Heidelberg: Springer, 2014.



Bibliographic reference

Topolov V.Yu., Bowen C.R. High piezoelectric performance of novel 1–3-type lead-free composites . International Journal Of Applied And Fundamental Research. – 2014. – № 2 –
URL: www.science-sd.com/457-24630 (28.03.2024).