Infrared sensor, Pyroelectric coefficient, electrical conductivity, Percolation threshold.

Transcription

1 Military Technical College Kobry El-Kobbah, Cairo, Egypt 10 th International Conference on Electrical Engineering ICEENG 2016 yroelectric araeters Measureent of Infrared Sensor Based on ANI- CSAVDFBaTiO 3 Coposite Fils By Mazhar B. Tayel 1, Moataz B. Solian 2 Shaker M. Ebrahi 2 and Ahed M. El-Shaer 1 * 1 Departent of Electrical Engineering, Faculty of Engineering, Alexandria University, lofty Elsied, Alexandria, Egypt, Materials Science Departent, Institute of Graduate Studies and Research, Alexandria University, 163 Horrya, Alexandria, Egypt, Abstract: An infrared sensor based on coposite of polyanilinepolyvinylidene fluoride (ANIVDF) bariu titanate (BaTiO 3 ) with different weight percentages (25, 50, 70 and 100) of BaTiO 3 has been fabricated. ANI doped with caphor sulfonic acid SA) was prepared cheically. Electrical easureents such as electrical conductivity and pyroelectric current and coefficient of these coposites were perfored. It was found that the pyroelectric coefficient increases with increasing of the weight percentage of BaTiO 3. The behavior of electrical conductivity of ANI-CSAVDFBaTiO 3 coposite fils with different weight percentages of BaTiO 3 was followed up the percolation theory. The percolation threshold value of ANI- CSAVDFBaTiO 3 coposite fils was found at 25 wt.% of BaTiO 3. The conductivity of the coposite fils was increased fro Sc 0 wt.% of BaTiO 3 to Sc at 100 wt.% of BaTiO 3. The pyroelectric coefficient values were enhanced fro to C 2 C at 0 wt.% and 100 wt.% of BaTiO 3, respectively. Keywords: Infrared sensor, yroelectric coefficient, electrical conductivity, ercolation threshold. * Corresponding to Ahed Mohaed El-Shaer, Departent of Electrical Engineering, Faculty of Engineering, Alexandria University, Alexandria, Egypt, Tel , E-ail: ahshaer@alexu.edu.eg, ahshaer1@yahoo.co.

2 1. Introduction: yroelectric sensors are widely used in applications like Radiation Theroeter, Fire Detectors, Theral Iaging, Medicine, Industry, Counications [1,2]. For any applications a high pyroelectric paraeters are required. In order to get axiu pyroelectric paraeters, several approaches were already investigated, for exaple the appropriate choice of pyroelectric paraeters, special construction techniques to reduce the heat conduction away fro the sensitive eleent or the use of theral absorber layers [3,4]. yroelectric aterials are polar and respond to theral energy by a change in spontaneous polarisation. This process is dependent on the change in teperature induced in the aterial. A nuber of pyroelectric aterials are available. Soe of these are single crystal (LiTaO 3 ), Triglycine Sulphate: TGS, or ceraic (btio 3, BaTiO 3 ). Ceraic aterials such as BaTiO 3 has very good pyroelectric properties and used in a variety of applications. But their brittle nature and inflexibility liit their use in soe applications. Recently polyers like polyvinylidene fluoride and its co-polyers such as vinylidene fluoride have been used in pyroelectric sensors. However, the low pyroelectric coefficients of such aterials and the difficulties involved in poling the thick fils restrict their use. Therefore, a coposite consisting of highly pyroelectric ceraic aterial cobined with a polyer would be the ideal replaceent for obtaining the properties of both these classes. Such a coposite would exhibit the pyroelectric coefficient of the ceraic aterial and the flexibility and strength of the polyer [5]. The ai of this work is to exaine the electrical conductivity and pyroelectric coefficient) of the coposite fils prepared by casting technique as a pyroelectric infrared sensors. 2.Experiental Work: 2.1 Synthesis of olyaniline: olyaniline eiraldine salt ANI-ES doped for was prepared by cheical oxidative polyerization with hydrogen peroxide as an oxidant. Typically 8 g (6.57 l) of aniline was dissolved in 900 l hydrochloric acid 1 M (doping agent), and then 0.02 g of ferrous chloride (FeCl 2 ) was dissolved in 225 l deionized water. The two solutions were then ixed in beaker and stirred with a agnetic stirring bar. During stirring 100 l of hydrogen peroxide (H 2 O 2 ) (6 %) was drop wise added to the solution to initiate the polyerization. The stirring was continued for 48 hr to ensure the copletion of polyerization. The green powder (ANI-ES) was collected on a filter paper using vacuu filtration and washed with water until filtrate becae colorless, then dried at 50 º C for 24 hr. The ANI was undoped with aonia solution (5 %) and stirred for 3 hr. The blue powder was collected on a filter paper using vacuu filtration and washed with water until filtrate becae neutral, then dried at 50 º C for 24 hr.

3 2.2 reparation of Bariu Titanate Bariu titanate powder is synthesized using the standard solid state reaction technique. The raw aterials used were BaCO 3, TiO 2. The powders are weighted in stiochioetric proportion and grinding in wet ixed in acetone ediu using a ball ill for durations up to 6 hr, in an agate jar with agate balls. The ballsaple ass ratio was 20:1. This power ixture is therally treated at 1000 C for 4 h at roo teperature to obtain the perovskite phase. Heat treated powder is finally ground and sieved through a esh to obtain particle of size less than 50 µ. 2.3 reparation of ANI-CSAVDFBaTiO 3 Coposite Fils Coposites of ANI-CSAVDFBaTiO 3 are prepared by ixing of solution of ANI- CSA and VDF which are soluble in DMF with BaTiO 3. Two gras of VDF granules are dissolved in 20 l of DMF for 2 hours and the polyaniline doped with CSA is prepared by adding 0.25 gs of polyaniline to g of CSA in 20 l of DMF with continuous stirring for 48 hours at roo teperature. Coposites of ANI- CSAVDFBaTiO 3 having 0, 25, 50, 75, and 100 % by weight are prepared by introducing 0, , , , and g of BaTiO 3 respectively to 4 l of ANI-CSAVDF. After stirring for 4hr, the resulting solutions are cast. 2.4 Electrical Measureents The pyroelectric detector is essentially a capacitor that can be charged by an influx of heat. The detector does not require any external electrical bias. It needs only an appropriate electronic interface circuit to easure the charge [6]. Figure 1 shows a pyroelectric detector connected to a resistor R G that represents either the internal leakage resistance or a cobined input resistance of the interface circuit connected to the sensor. The equivalent electrical circuit of the sensor is shown on the right. It consists of three coponents: (1) the current source generating a heat induced current, Ip, (2) the sensor's internal capacitance, C A, (3) the internal resistance, R A. Figure (1): yroelectric detector and its equivalent circuit.

4 The electrical conductivity of the blend fils is easured by the two probe ethod. The thin fil saples are coated with silver paste onto the two both sides and ounted on the two probe holder designed on the printed circuit board (CB) as shown in Figure Conductivity Measureents Figure (2): Two probe holder designed on the CB. The electrical conductivity of ANI-CSAVDFBaTiO 3 coposite fils is easured at different teperatures by using the syste shown in Figure 3a. A bias voltage V in the range fro 0.2 to 4 V was applied by using Kiethley power supply instruents 240A. The teperature is varied fro 20 C to 100 C. The easured current pass across the saple is easured by Kiethley 616 digital electroeter with the increase of teperature with a rate of 5 Cin inside a GC-TZN4M Autonics furnace. The electrical resistance R is calculated fro the I-V characteristics at a constant voltage and the resistivity ρ is then calculated at different teperatures using the definition: ρ = R Ad (1) where A is the area of the electrodes and d is the thickness of the saple. The electrical conductivity σ can be coputed by using the definition: σ = 1ρ (2) yroelectric Current and Voltage Measureent The pyroelectric detector, as shown in Figure 3b, is a capacitor fored by depositing etal electrodes on both surface of the thin slice of pyroelectric aterial. The pyroelectric specien is heated at a variable teperature chaber. The change in the value of dt, which causes a polarization change, and, consequently, results in

5 displaceent of electric charges in the pyroelectric aterial, hence the pyroelectric current Ip takes place [7,8]. (a) Figure (3): Measureent setup of a) I-V characteristics, b) the pyroelectric current. The pyroelectric current depends on the teperature change with tie. Therefore, pyroelectric devices are considered to be alternating current (AC) coupled devices. The pyroelectric current is proportional to the area (A) and the rate of change of teperature (dtdt) of the detecting eleent according to the following equation [3]: (b) =.., =. (3) When, the detector is heated by incident radiation, the polarization changes by the aount of incident radiation deterined by the teperature change and the pyroelectric coefficient of the aterial [4]. 3. Result and Discussion: 3.1 Electrical Conductivity of ANI-CSAVDFBaTiO 3 Coposite: Figure 4 presents the electrical conductivity of the ANI-CSAVDFBaTiO 3 coposite fils as function of BaTiO 3 loading. It shows that the conductivity increases slightly fro 0 wt.% to 25 wt.% of BaTiO 3 this is attributed to doping effect of CSA which axiizes the nuber of carriers the highest nuber of carriers can be connected with the delocalization effect of doping process and foration of the polarns or bipolarons in the coposite structure as discussed by [9]. According to electron transport echanis adding BaTiO 3 with lower wt.% to ANI increase the crystallinity of ANI, and the charge transport is liited, which indicates a stronger localization of charge carriers and

6 thus represents a lower electrical conductivity [10]. The electrical conductivity of the ixture of two the aterials with different conductivities can be predicted by the percolation theory. The conductivity of pure ANI-CSAVDF coposite fil is Sc and its increased to Sc at 25 wt.% of BaTiO 3. At 50 wt.% loading of BaTiO 3 the conductivity of the coposites jups drastically to Sc. Fro Figure 4, we can conclude that percolation threshold is 25 wt.% of BaTiO 3. At higher loading of BaTiO3 over the 50 wt.%, the conductivity is saturated in the range of Sc and Sc for 75 wt.% and 100 wt.% of BaTiO 3 respectively. The slightly increase in electrical conductivity which is due to the particles blockage of conduction path by the BATiO 3 nano-particles ebedded in the ANI atrix, which indicates a weaker localization [9]. 1.E-04 1.E-05 ) (sc s 1.E-06 1.E-07 1.E-08 0% 25% 50% 75% 100% BaTiO3(wt.%) Figure (4):Dependence of electrical conductivity of ANI-CSAVDFBaTiO 3 coposite fils versus wt.% of BaTiO 3 at roo teperature. 3.2 yroelectric roperties of ANI-CSAVDFBaTiO 3 Fils: Figure 5 shows the pyroelectric coefficient p of coposite fils of ANI- CSAVDFBaTiO 3 with different wt.% of BaTiO 3 at different teperature range fro 20 to 100 C with rate of 1 Cin. For pure ANI-CSAVDF with (0 wt.% of BaTiO 3 ), the pyroelectric coefficient is steeply increased to C 2 C in the range fro 20 to 40 C and has a broad peak at 50 C. This peak is due to the presence of the dipole oents which are aligned in the β-phase resulting in strongest dipole oent per unit cell of the VDF. yroelectric coefficient is decreased beyond 50 C due to the release of charge trapped at crystallineaorphous boundaries and a rise of α-

7 phase in VDF polyer [11]. The oveent of ions at side chain for dipoles which are returned to a randoly oriented state which is referred to as dipolar relaxation. This β-phase dipoles relaxation is associated with the dipole orientation of the polar side group of the VDF [5]. By increasing BaTiO 3 in the ANI-CSAVDFBaTiO 3 coposite fils the pyroelectric coefficients value is increased two orders of agnitude. For 25 wt.%, 50 wt.%, and 75 wt.% of BaTiO 3, the pyroelectric coefficient values are equal to C2 C, C 2 C and C 2 C respectively at roo teperature as shown in Figure 5. Also, the delay increased of pyroelectric coefficient fro 20 C to 60 C ay be due to the existence of the dipoles of BaTiO 3 which are transfor β-phase to α-phase dipoles of the VDF. Fro 60 C to 80 C the current was increased which reaches to peak at 80 C due to the transforation fro α-phase to β-phase dipoles [11]. Above 80 C the pyroelectric coefficient is decreased for 50 wt.% and 75 wt.% of BaTiO 3, this is due to the release of charge trapped at crystallineaorphous boundaries [12]. At 100 wt.% of BaTiO 3, the pyroelectric coefficient increased in the range of 20 C to 40 C and is equal to C2 C at roo teperature. 2.55E E E E E E E E E E E E-05 0 wt.% BaTiO E wt.% BaTiO E E E E E E wt.% BaTiO E E E wt.% BaTiO E E E E E E E E E E E E-05

8 1.34E E E E E E E E E wt.% BaTiO E-03 Figure (5): yroelectric coefficients of ANI-CSAVDFBaTiO 3 coposite fils with different wt.% of BaTiO Conclusions: Coposite fils of polyaniline doped with caphor sulfonic acidpolyvinylidene fluoridebariu titanate were successfully prepared with different weight percentages of BaTiO 3. Experientally, it is observed that, the conductivity of the coposite fils was increased fro Sc 0 wt.% of BaTiO 3 to Sc at 100 wt.% of BaTiO 3. The percolation threshold of this coposite was found to be 25 wt.% of BaTiO 3. This low percolation threshold will allow the use of the prepared coposite fil for infrared sensor applications. The pyroelectric current was easured by increasing teperature with rate 1 Cin and then the pyroelectric coefficients were calculated. The pyroelectric coefficient values were enhanced fro to C 2 C at 0 wt.% and 100 wt.% of BaTiO 3, respectively. References: [1]Kateb, B., Yaaoto, V., Yu, C., and Grundfest, W., Infrared Theral Iaging: A Review of the Literature and Case Report, Neuroiage, vol. 47, no.2, pp , [2]Mahulikar, S.., Rao, G. A., and Sonawane, H. R., Infrared Signature Studies of Airborne Target, roceedings of the International Conference on Aerospace Science and Technology Bobay, India, pp , [3]Rogalski, A., Infrared detectors, 1st edition, CRC ress, [4]Charlot, B., s. Gauthier, S., Garraud, A., and Giani, A., VDFMMA Blend yroelectric Thin Fils, Journal of Materials Science: Materials in Electronics, vol. 22, no. 12, pp , 2011.

9 [5]Muralidhar, C., and illai,. K. C., yroelectric Behavior in Bariu Titanteolyvintlidene Fluoride Coposites, IEEE Transactions Electrical Insulation, vol. 3, pp , [6]Lang, S. B., SourceBook of yroelectricity, 1st edition, Gordon and Breach Science ublishers, CRC ress, [7]Odon, A. Modelling and Siulation of the yroelectric Detector Using MATLABSiulink, Measureent Science Review, vol. 10, no. 6, pp , [8]Odon, A., rocessing of Signal of yroelectric Sensor in Laser Energy Meter, Measureent Science Review, vol. 1, pp , [9]atil, S. L.,Chougule M. A., and Shashwati, S., Effect of Caphor Sulfonic Acid Doping on Structural, Morphological, Optical and Electrical Transport roperties on olyaniline-zno Nanocoposites, Soft Nanoscience Letters, vol. 2, no. 2, pp. 1-8, [10]Zhang, X., Wei, S., Haldolaarachchige, N., and Guo, Z., Magnetoresistive Conductive olyanilinebariu Titanate Nanocoposites with Negative erittivity, Journal of hysical Cheistry C, vol. 116, no. 29, pp , [11] Saidi, S., Ayen, M., Bouzitoun, M., and Mohaed, A. B. Effect of α-to β- Transforation on the DC and AC Conductivity Mechanis in olyaniline: olyvinylidene Fluoride Coposites Fils, Materials Science in Seiconductor rocessing, vol. 26, pp , [12]Shukla,., and Gaur, M. S., Therally Stiulated Depolarization Current and Dielectric Relaxation Spectroscopy in olyvinylidene Fluoride Saples, Iranian olyer Journal, vol. 17, no. 3, pp , 2008.