Enhancement of piezoelectric and pyroelectric properties of composite films using polymer electrolyte matrix

Abstract

Composite films consisting of lead zirconate titanate ͑PZT͒ inclusions dispersed in a matrix of polymer electrolyte the polyethylene oxide were fabricated. Their piezoelectric coefficients d 33 and pyroelectric coefficients p are increased almost proportional to the volume fraction of the ferroelectric ceramic phase. For 34% PZT composite, d 33 and p are 170 pC/ N and 120 C / m 2 K, respectively, they are much larger than PZT/polyvinylidene fluoride-trifluoroethylene composite with similar ceramics content. It is believed that the enhancement of the measured coefficients is due to the relatively high electrical conductivity of polymer electrolyte matrix. This is confirmed by theoretical models which consider the conductivity of matrix. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2827571͔Composites of polymer matrix mixed with ferroelectric ceramics have been well studied and their pyroelectric and piezoelectric properties are widely applied in various areas. [1][2][3][4][5][6] The ferroelectric ceramics inclusions play the role to provide the functional effects and the polymer matrix usually serves to provide good protection of the ceramic phase while maintains the compliant mechanical property. The advantages of these polymer composites with piezoelectric or pyroelectric functions are that they can be easily made to large area to increase sensitivity as sensors, they are flexible that intimate contact with the objects to be detected is possible, this is particularly important in vibration sensing application. However, even though the functional ceramics have high piezoelectric and pyroelectric coefficients, the effective coefficients of the composites are relatively low, for example, the pyroelectric coefficients p of lead zirconate titanate ͑PZT͒ ͑30 vol % ͒/polyvinylidene fluoridetrifluoroethylene ͑PVDF-TrFE͒ is 21% of the pure PZT ceramics at room temperature, 7 as their p's are 73 and 352 C / m 2 K, which hinders the realization of practical use of the polymer composites.From our previous study, 8 a 0-3 composite of 30 vol % PZT with a thermoplastic polyurethane ͑PU͒ shows a pyroelectric coefficient of 90 C / m 2 K at room temperature, around 27% of pure PZT, which is much higher than the PZT/PVDF-TrFE composite of the same ceramic volume fraction. As the PU used in the study has a higher electrical conductivity than other insulating polymers, this interesting result reveals the contribution of the electrical conductivity of the matrix which would enhance the pyroelectric coefficient of the composites. 8 It also encourages the application of other polymeric materials which has higher conductivity to further enhance the pyroelectricity or even piezoelectricity. Polyethylene oxide ͑PEO͒ is a well known polymer electrolyte which has been demonstrated a useful solid electrolyte for lithium battery. 9 The neat PEO has higher conductivity than PU by three orders of magnitudes. According to the theoretical model developed in the previous study, the PZT/ PEO composite is expected to have even a higher pyr...

Enhancing pyroelectric and ferroelectric properties of PVDF composite thin films by dispersing a non-ferroelectric inclusion La2O3 for application in sensors

“…Among these four common polymorphs, only Form II is nonpolar, and the remaining three are polar. In a vector sum of constituent dipoles, the spontaneous polarization of Forms III and IV is around half that of Form I. Composites of a polymer matrix mixed with ferroelectric ceramics have attracted much attention from scientific communities because of their exceptional pyroelectric and ferroelectric properties [1][2][3][4][5][6][7][8]. Ferroelectric ceramic inclusions play an important role in providing functional effects to composite thin film, but have poor mechanical properties.…”

The effect of processing conditions on the morphology, thermomechanical, dielectric, and piezoelectric properties of P(VDF-TrFE)/BaTiO3 composites

“…As pointed out in a recent review [33], modification of the surface of the ceramic fillers, through chemical grafting or the production of core-shell structures is key to improve filler dispersion, reduce porosity, thereby improving the mechanical, and electrical properties of the composites. Most of the existent studies focus on the dielectric [34][35][36][37][38][39][40][41][42][43] and electromechanical [4,7,13,15,17,25,44] properties of such composites and relatively few systematic studies on their thermal and mechanical behavior have been published so far. Furthermore the ceramic volume fractions considered are often much lower than those used in most applications [45], studies of highly filled composites mainly being limited to lead-based ferroelectric materials [46,47].…”

“…Lead containing perovskites, and particularly PZT (Pb(Zr,Ti)O 3 -lead zirconium titanate), are at present the most widely used materials for sensors, actuators, and other electronic devices because of their excellent piezoelectric properties, ease of fabrication, and low cost manufacturing [14]. Hence, most of the studies on piezoelectric ceramicpolymer composites with high-piezoelectric activity deal with PZT-based materials [7,12,13,[15][16][17]. However, for environmental and health concerns it is desirable to substitute PZT with a lead-free piezoelectric ceramic and BaTiO 3 may offer a convenient alternative [18].…”

“…As (0-3) composites are easier to manufacture and shape than composites with other connectivity patterns, a large research effort is taking place to improve their piezoelectric coefficient. Several polymers have been used as matrices for such composites, including, e.g., epoxy resins [4,5], chloroprene [6], polyethylene oxide [7], and polyamides [8,9]. Polyvinylidene fluoride (PVDF) and its copolymer with trifluoroethylene, P(VDF-TrFE), have raised particular interest as they have large relative permittivity and high dielectric strength, and exhibit themselves a relatively large piezoelectric activity.…”

Mechanical properties and connectivity evaluation of a conductive coated piezoceramic/polymer composite

“…1,2 Although the polymer matrix-based ferroelectric composites are a promising alternative, its use has limitations which arise by the individual characteristics of the phases of the composite sample: One limitation is the low permittivity of the polymer phase that hinders the poling process of the ceramic phase. [3][4][5] Another is the composite's low ceramic content, which results in low piezo-and pyroelectric coefficients.…”