Synthesis and thermoelectric properties of polyaniline zinc oxide composites: A study on temperature-dependent conductivity and seebeck coefficient

Abstract

Polyaniline zinc oxide (PANI-ZnO) composites were synthesized via a chemical route, varying zinc oxide content from 20 wt.% to 25 wt.%. The structural integrity of the PANI-ZnO composites was confirmed through X-ray diffraction (XRD) analysis. Two-probe measurements were conducted to evaluate DC conductivity as a function of temperature in the range ( $303 K t o 423 K$ ). At 0 wt.%, the conductivity ranged from 4.88 × 10⁻⁵ $S / c m$ at $303 K$ to 1.43 × 10⁻⁴ $S / c m$ at $423 K$ . For the 20 wt.% composite, the values were 2.3 × 10⁻⁶ $S / c m$ at 303 K and 2.5 × 10⁻⁴ $S / c m$ at $423 K$ . Notably, the 25 wt.% composite exhibited enhanced conductivity, reaching 6.12 × 10⁻⁴ $S / c m$ at $423 K$ and 1.0 × 10⁻⁷ $S / c m$ at $303 K$ . The observed semi-conducting behaviour, with conductivity increasing with temperature, highlights the potential of these materials for thermoelectric applications. Additionally, the Seebeck Coefficient of all samples linearly raises with increasing temperature and concentration of Zinc oxide, and reaching the maximum 50 $μ V / K$ from 30 $μ V / K$ at $373 K$ , which suggests that the synthesized materials may be good candidates for thermoelectric devices. Scanning electron microscopy (SEM) revealed a dual-phase morphology with platelet and flaky structures interlocked by granular particles, emphasizing the structural robustness of the composites.

Keywords

polyaniline zinc oxide composites DC conductivity seebeck coefficient x-ray diffraction thermoelectric materials SEM temperature-dependent conductivity

Introduction

Conducting polymers have garnered significant interest for applications ranging from organic electronics and energy storage devices to anticorrosion coatings. Their unique properties arise from a chemical polymerization process in which small monomer units react to form long, interconnected chains or three‐dimensional networks. The degree of polymerization (DOP), which indicates the number of monomers that join during the reaction, is a key factor in determining the structural and functional properties of the resulting polymer.¹

Among these materials, polyaniline (PANI) is particularly noteworthy due to its ease of synthesis, environmental stability, and adjustable electrical conductivity. Aniline (C₆H₅NH₂) the building block for PANI has diverse applications in industries such as dye manufacturing, biomedical research, and even aerospace, highlighting the versatile nature of its derived polymer.² Conductive polymers like PANI, often described as “synthetic metals,” exhibit remarkable magnetic, electrical, and optical properties, making them suitable for advanced devices including organic solar cells, light-emitting diodes, and biosensors.^3,4

A promising strategy to further enhance the performance of PANI is the incorporation of nanomaterials such as zinc oxide (ZnO) nanoparticles.^5–10 The formation of PANI–ZnO composites via chemical oxidative polymerization combined with sol–gel synthesis of ZnO has demonstrated notable improvements in properties such as crystallinity and conductivity.^11,12 ZnO nanorods, when integrated with the PANI matrix, not only influence the microstructure but also interact with the polymer chains to tailor the conduction and thermal behaviour of the composites.^13,14

Furthermore, optimizing the ZnO content and doping levels has proven critical in enhancing the DC conductivity and semiconducting behavior of these composites. For instance, an appropriate ZnO concentration has been shown to improve device performance in applications like supercapacitors, electrochromic batteries, and even in metal–insulator–semiconductor devices such as Schottky diodes.^15–17 These observations underscore the importance of nanoscale engineering in modulating the intrinsic properties of conductive polymers.

In this work, we present a comprehensive investigation into the synthesis, characterization, and electrical performance of PANI–ZnO nanocomposites. By systematically varying the ZnO content and employing advanced fabrication techniques, we aim to elucidate the interplay between the composite’s microstructure and its conductive properties. Our study not only deepens the understanding of doping and conduction mechanisms in PANI-based systems but also highlights their potential for practical applications in corrosion protection, thermoelectric devices, and energy storage systems.^18–23 This integrated approach to material design and characterization emphasizes the importance of tailoring composite materials to meet the demands of next-generation electronic and energy technologies.

Recent studies have continued to push the boundaries of PANI–ZnO nanocomposite research. For instance, Patel et al.²⁴ introduced a novel one‐pot synthesis technique that enhances the interfacial bonding between ZnO nanostructures and the PANI matrix. Their method simplifies the fabrication process while delivering composites with superior thermal stability and improved electrical conductivity. Similarly, Lee et al.²⁵ demonstrated that surface functionalization of ZnO nanoparticles can fine‐tune the optoelectronic properties of PANI–ZnO composites, which is critical for applications in flexible electronics and energy storage devices.

Experimental

Materials

The chemicals and reagents shown in Table 1 were used for synthesis of Polyaniline and PANI-ZnO composite. Ammonium persulfate (APS) [(NH₄)₂S₂O₈] (DUKSAN) which acts as an oxidizing agent, Hydrochloric acid (Anala R^R), Aniline [C₆H₅NH₂] (Riedel-de-Haen^R), Acetone, Zinc Oxide and Distilled water. All the chemicals were used without any further purification.

Table 1.

Synthesis of polyaniline and PANI-ZnO composite.

Sr No	Chemicals names with formulae	Molar mass $(g / m o l)$	Percentage purity	Source
1	Aniline (C₆H₇N)	93.13	99.1	Riedel-de-Haen^R
2	Distilled water	18.1	99.8	From lab
3	Ammonium persulfate (NH₄)₂S₂O₈	228	99.0	DUKSAN
4	Hydrochloric acid	36.43	75.5	Anala R^R
5	Zinc oxide	81.38	99.0	Sigma-Aldrich

Chemicals used in the synthesis of polyaniline/polyaniline-ZnO composite

Polyaniline was synthesized by a chemical polymerization of aniline monomer. A solution of ammonium persulfate (APS) was prepared by dissolving 10.00 g (0.05 M) of APS in 44 ml of distilled water. This mixture, which acts as an oxidizing agent, was stirred continuously using a magnetic stirrer for 30 min to form the APS solution. Additionally, 400 ml of distilled water and 5.00 ml of hydrochloric acid (0.13 M) were also used in the experiment. Highly dangerous fumes were emitted by the heating process, and the pH was adjusted up to 1. The APS solution was added drop by drop to the aniline HCl solution while it was being stirred continuously at 5°C. This process gives off heat, and it needs to be stirred for up to 4 h to complete polymerization.

After completed the polymerization process the precipitate was filtered and washed with distilled water multiple times to reduce its acidity and adjust its pH to neutral the residue was filtered using Whatman filter paper with the help of a vacuum pump and then left in open air to remove surface moisture. It was subsequently dried in a vacuum oven at 60°C for 24 h until a constant mass was achieved. The resulting dried sample of pure polyaniline was then ground using an agate mortar to obtain fine powder. The final yield of pure polyaniline was 4.00 g. ZnO composites with pure polyaniline were prepared by adding 20 wt.% and 25 wt.% ZnO to the filtered polyaniline solution, followed by stirring for 2 h.

Measurements

The X-Ray diffraction studies were performed using X-Ray diffractometer with Cu-K $\propto$ as a radiation source having wave length (λ = 1.5460 A°) MODEL (D8 ADVANCE). The X-Ray diffraction diffractograms were recorded in the term of 2θ range 20° $\leq 2 θ \leq$ 90° with the scanning rate of 3°/minute. The electrical D.C conductivity of all prepared sample were calculated by using KEITHLEY source meter 2400 by using 2-probe method having voltage range $\pm$ 20 $V$ was selected. The D.C conductivity of Polyaniline is deliberate by temperature dependent by using 2-probe method thin film of Polyaniline and its composites were prepared on glass plate by using doctor-blade-method. The device architecture of the seebeck having hot plates and a Nano-voltmeter 2182 A KEITHELY were used to measure the temperature gradients and voltage difference. with four wires, one pair of wire contact used for measuring voltage by varying the temperature $(40 ° C t o 100 ° C)$ by using hot plate. The data were used to calculate the seebeck coefficient. The glass plate was placed on hot plate and its temperature was raised gradually from $(313 K t o 373 K)$ , the contact difference about $2 c m$ kept constant at various temperature, were connected with Nano-voltmeter $2182 A$ . Temperature dependence on seebeck coefficient, the ratio of the potential difference to the temperature difference was measure by Nano voltmeter $2182 A$ KEITHELY. Seebeck coefficient S is described as

S = \frac{Δ V}{Δ T}

where

∆

T is the temperature difference between the hot and cold surface of the sample and

∆ V

is the seebeck voltage. Its unit is

m V / K o r μ V / K

. Scanning electron microscopy was carried out by using an EVO50 ZEISS instrument.

Results and discussion

X-ray diffraction

X-Ray diffraction has been achieved from Institute Advanced Material (IAM) from BZU, Multan. The X-Ray diffraction pattern of PANI and PANI-ZnO composites also studied in this chapter. These tools have a wavelength of 1.54 A° by using Cu-K $\propto$ source radiations. Various diffraction patterns of PANI, PANI 20 wt.% ZnO and PANI 25 wt.% ZnO has been display in Figure 1. The reduction of amorphous nature into whole crystallinity of all sample depends upon the condition at which all sample is synthesis. By using the following Bragg’s equation, d_hkl- spacing values of all observed peaks in sample have been calculated.

2 \times d_{hkl} \sin θ = n \times λ

(1.1)

Figure 1.

X-Ray diffraction pattern of pure polyaniline.

X-ray diffraction of polyaniline

The X-Ray diffraction analysis mechanisms is used to determine the different crystallinity structure which is present in Polyaniline. The structural behaviour of PANI and PANI-ZnO composites were studied by X-Ray diffraction. The X-Ray diffraction studied of Polyaniline reveal a broad peak at angle (degree) 2θ = 25.30°. This broad peak which is appear in the X-Ray diffraction pattern reveal the amorphous nature.

X-ray diffraction of zinc oxide (ZnO)

Figure 2 shows the X-Ray diffraction pattern of pure Zinc oxide (ZnO). X-Ray diffraction results declares that Zinc Oxide are well crystalline where highest intense peak is observed. The existence of sharp peaks indicates that the powder was crystalline and the single phase of ZnO. PANI-ZnO composites shows ZnO peaks as well as PANI, indicated that ZnO crystallite have been uniformly mixed with PANI.²⁶

Figure 2.

X-ray diffraction of Zinc oxide.

X-ray diffraction analysis of ZnO

The XRD pattern of zinc oxide were analysed by matching the observed peaks with the standard pattern by (jcpd card NO 36-14151) which is reported in literature in following Table 2 a number of strong reflections observed at 33.2°, 39.9°, 46.6°, 50°, 52.1°, 56.6°, 60.9°, 68.1°, 70.9°, 82° and 86.5°, all characteristics peaks are good agreements of hexagonal quartzite structure.

Table 2.

X-ray diffraction analysis of zinc oxide (ZnO).

(hkl) planes	Jcpd 2θ (degree)	Calculated 2θ (degree)	d_hkl jcpd	d_hkl calculated	Difference $∆$ d (A^o)
(100)	31.79	33.2	2.81	2.69	0.12
(002)	34.44	39.9	2.60	2.25	0.35
(101)	36.27	46.6	2.47	2.94	0.471
(102)	47.57	50	1.910	1.824	0.086
(110)	56.63	52.1	1.623	1.753	−0.13
(103)	62.90	56.6	1.477	1.6244	−0.147
(200)	66.42	60.9	1.405	1.519	−0.114
(112)	68.00	68.1	1.377	1.37	0.007
(201)	69.14	70.9	1.358	1.32	0.038
(004)	72.62	82	1.300	1.173	0.127
(202)	77.02	86.5	1.237	1.12	0.1179

Average of Δ d = \pm 0.0018 (A °)

X-ray diffraction of polyaniline-zinc oxide (PANI-ZnO composite)

Figure 3 shows the X-Ray diffraction pattern of PANI-ZnO composites by increase the concentration 20 wt.% and 25 wt.% of ZnO in Polyaniline chain. PANI-ZnO composites gives the highest sharp peaks of ZnO with Polyaniline which confirmed that the crystallinity of ZnO have been consistently mixed within the Polyaniline chain. It is confirmed that PANI interrelate with ZnO particles and the PANI molecular chain are stressed and leading to lower crystallinity. The peaks position of PANI-ZnO composites were shifted toward the small angle, the intensity of peaks increasing by increase the wt% of ZnO content in Polyaniline chain.

Figure 3.

X-ray diffraction of (a) PANI 20 wt.% ZnO (b) PANI 25 wt.% ZnO in stacking form.

D.C conductivity of polyaniline and PANI-ZnO composites

The D.C conductivity of Polyaniline is deliberate by temperature dependent by using 2-probe method and followings Figure 4 shows the variation of D.C conductivity at different temperature of pure PANI and PANI-ZnO composites. In both cases observed that conductivity was going to increase by increasing the temperature and wt.% of composite.

Figure 4.

Conductivity (σ) versus Temperature dependent for (a) polyaniline (b) PANI 20 wt.% ZnO (c) PANI 25 wt.% ZnO.

Conductivity was increased by increasing the wt.% of ZnO, the reason is that carrier concentration is proportional to the conductivity. ZnO is the n-type semi-conductor which having large band gap about 3.4 $e v$ so, by increasing the carrier concentration conduction mechanism enhance.

Conductivity was also increased by increasing the temperature, the reason is that the efficiency of charge transfer increase and the covalent bonds was broken easily which was present between PANI and PANI-ZnO Composites. Its resistance decreased so; conductivity increased by increasing the temperature.

Here the conductivity of the Polyaniline is increased by increasing the temperature $(303 K t o 423 K)$ about 4.88 $\times$ 10⁻⁵ $S / c m a t 303 K$ and about 1.43 $\times$ 10⁻⁴ $S / c m$ at 423 $K$ .

By increasing the concentration of the composite, the conductivity of the Polyaniline also raised about at 0 wt.% of composite is 1.43

\times

10⁻⁴

S / c m

and at 25 wt.% of composite is 6.12

\times

10⁻⁴

S / c m

are shown in Table 3.

Table 3.

Conductivity(σ) versus temperature dependent for (a) Polyaniline-25 wt.% ZnO (b) PANI-20 wt.% ZnO (c) pure PANI.

Temperature $(K)$	Conductivity of pure PANI σ = $\frac{1}{R} \times \frac{L}{A}$ $(S / c m)$	Conductivity of PANI-20 wt.% ZnO σ = $\frac{1}{R} \times \frac{L}{A}$ $(S / c m)$	Conductivity of PANI-25 wt.% ZnO σ = $\frac{1}{R} \times \frac{L}{A}$ $(S / c m)$
303	4.88 $\times$ 10⁻⁵	2.3 $\times$ 10⁻⁶	1.00 $\times$ 10⁻⁷
333	2.3 $\times$ 10⁻⁵	5.222 $\times$ 10⁻⁵	1.24 $\times$ 10⁻⁴
363	1.88 $\times$ 10⁻⁵	9.51 $\times$ 10⁻⁵	2.40 $\times$ 10⁻⁴
393	7.07 $\times$ 10⁻⁵	1.70 $\times$ 10⁻⁴	3.98 $\times$ 10⁻⁴
423	1.43 $\times$ 10⁻⁴	2.5 $\times$ 10⁻⁴	6.12 $\times$ 10⁻⁴

Temperature dependent D.C conductivity

The relation between temperature and dc conductivity in polymer can provide essential information about the nature of phenomenon correlated with charge transport mechanism into a polymer

σ = σ_{0} {\exp (- \frac{To}{T})}^{1 / 1 + n}

(1.2)

Now exponent n in the above equation is the effective dimensionally for charge transport mechanism that may depend upon inter chain coupling, “n” is the positive integer 1, 2, 3…for 1-dimension, 2-dimension or 3-dimension respectively variable range hopping model which is proposed by Mott charge transport mechanism.

The nearest neighbour Hopping process with a distribution of Activation energies can give the same type of exponential temperature dependence for conductivity.

The Activation energy is defining as

E_{a} = \frac{d (\ln σ)}{d (1 / KT)}

where E_a, K and T are the activation energy, Boltzmann constant and absolute temperature of the pellet respectively.

Activation energy of PANI and PANI-ZnO composite

When Polyaniline was doped with Zinc Oxide $(Z n O)$ then the conductivity of $Z n O$ doped Polyaniline is shown in Figure 4. The variation of D.C conductivity is discussing as a function of temperature of PANI and $P A N I - Z n O$ composites shown in Figure 4. In both cases observed that as conductivity of doped Polyaniline increases as temperature increases. Its conductivity is rapidly increased by raising the temperature because the efficiency of charge transfers rapidly increased. The conductivity of composites is going to be increased as compared to the PANI over the temperature range $(303 K - 423 K) .$

Here we observed that activation energy about at 0 wt.% of composite is 5.419 $\times$ 10⁻⁵ $e V$ and at 25 wt.% of composite is 1.705 $\times$ 10⁻⁵ $e V$ . The density of states increased and charge carriers also increased So, the activation energy of Polyaniline rapidly decrease by in increasing the concentration of the composite.

In Figure 5 by using linear fitting on the calculated data the slope $(\frac{1}{R}) = \frac{1}{v}$ which is the ratio of current (mA) and voltage(v) is obtained by using Origin pro-8, calculate the value of resistance R by using the ohm law, put in conductivity formula σ = $R \frac{L}{A}$ . Activation is calculated by taking the linear fitting of above a, b and c curve, then multiple the slop with the Boltzmann constant $0.89 (e V / K)$ , it was observed the activation energy is linearly decreased rapidly by increasing the concentration of the Zinc oxide in the Polyaniline chain

Figure 5.

Conductivity (σ) versus 1/temperature (K ⁻¹) dependent for (a) PANI-25 wt.% ZnO (b) PANI-20 wt.% ZnO (c) polyaniline.

Activation energy

By using Arrhenius’s exponential equation, the activation energy of the polymers at various temperature calculated are shown in Table 4.

σ = σ_{0} e^{- E / KT}

(1.3)

Table 4.

Activation energy of PANI, PANI-ZnO 20 wt.% &PANI-ZnO 25 wt.%.

Sample name	Boltzmann constant (K_β ) $e V / K$	Slope $(m)$	Activation energy (E_a) = m $\times$ k $(e V)$
PURE PANI	8.616 $\times$ 10⁻⁵	0.62905	5.419 $\times$ 10⁻⁵
PANI-20 wt.% ZnO	8.616 $\times$ 10⁻⁵	0.26371	2.272 $\times$ 10⁻⁵
PANI-25 wt.% ZnO	8.616 $\times$ 10⁻⁵	0.1980	1.705 $\times$ 10⁻⁵

taking log on both side above equation

\ln σ = \ln σ_{0} - \frac{E}{K} \times \frac{1}{T}

(1.4)

Y = c + m \times X

(1.5)

Compare equations (1.4) and (1.5)

Slope is calculated by m = - $\frac{E}{K}$

Activation energy is obtained by E_a = m $\times$ k

Activation energy versus content of ZnO (wt.%)

In Figure 6 shows that activation energy decreases rapidly by increases the wt.% of ZnO in Polyaniline chain. Activation energy is the minimum amount of energy is required to initiate the chemical reaction in a system.

Figure 6.

Plot of activation energy versus wt.% of ZnO in PANI.

The activation energy is calculated from the above equation the slope is m = - $\frac{E}{K}$ , Activation energy is obtained by E_a = m $\times$ k, m is slope of conductivity versus temperature which is obtain from pro-origin by linear fitting and K is the Boltzmann constant 8.616 $\times$ 10⁻⁵ $e V / K$ . The S.I unit of the activation energy is $(e V) .$ It has always positive value.

Device fabrication for seebeck measurement

The filtered pastes of PANI, PANI-20 wt.% ZnO, and PANI-25 wt.% ZnO were washed several times with distilled water to remove acidity and adjust the pH to neutral. The sample was despite on glass slide by using Doctor-blade-method, at the specimen stage pressure contact made by using copper wire. The one end of glass slide place under the tungsten hot plate and other end at room temperature. The pressure contact attach with nano-voltmeter by changing the temperature Seebeck voltage was measured are shown in Table 5.

Table 5.

Seebeck coefficient of PANI&PANI-ZnO.

Temperature $(K)$	Seebeck coefficient of PANI $(μ V / K)$	Seebeck coefficient of PANI-ZnO $(μ V / K)$
313	0	16
333	10	26
353	16	38
373	30	50

Seebeck coefficient of polyaniline and PANI-ZnO composite

Figure 7 shows the Seebeck coefficient graph of Polyaniline and Polyaniline-composites. The graph shows that Seebeck coefficient (S) of PANI-composites rapidly increase than pure Polyaniline. By increasing the temperature and wt.% of ZnO Seebeck coefficient increased, the reason is that the efficiency of charge carriers was increased so, more Seebeck voltage is created so, Seebeck coefficient was increased. Seebeck coefficient range of Polyaniline is $0 μ V / K - 30 μ V / K$ at temperature range $(313 K - 373 K)$ , Seebeck coefficient range of Polyaniline composite is $16 μ V / K - 50 μ V / K$ at temperature range $(313 K - 373 K) .$

Figure 7.

Seebeck coefficient of (a) PANI- 20 wt.% ZnO and (b) PANI- 25 wt.% ZnO.

Scanning electron microscopy (SEM)

The SEM image of pure PANI exhibits complete amorphous regions as shown in (Figure 8(a)). This image clearly reveals that surface of PANI is not smooth. Uneven lumps and holes visible in PANI are suitable for adsorption. It is found that the doping of ZnO has a strong effect on morphology of the resulting PANI-ZnO composites (Figure 8(b) and (c)). In case of PANI-ZnO composites, the SEM micrographs revealed a dual phase, the platelet as well as the flaky structure with an interlocking arrangement of granular particles. This suggests that most of ZnO nanoparticles coated with PANI and have formed a network during the polymerization process.

Figure 8.

Scanning electron micrographs (SEM) of (a) pure ZnO (b) pure PANI (c) PANI-ZnO.

Computational analysis

This study demonstrates significant advancements over previous works on PANI/ZnO systems. By incorporating a higher ZnO content (20–25 wt.%), it transitions from nanocomposites to composites, achieving superior DC conductivity (6.12 × 10⁻⁴

S / c m

) and an enhanced Seebeck coefficient

(50 μ V / K)

423 K

. Unlike earlier studies with lower ZnO concentrations, this work also explores a broader temperature range

(303 K - 423 K)

and provides advanced structural insights, such as dual-phase morphology, which contribute to improved material performance. These advancements highlight the potential of PANI-ZnO composites for high-efficiency thermoelectric applications.

Parameter	This study	Tripathi et al. (2023)²⁰	Zhang et al. (2020)²²	Gupta et al. (2024)²⁷	Advancement in this study
ZnO content (wt.%)	20–25	≤15	≤10	10–20	Higher filler concentration explored, transitioning from composites to composites
DC conductivity $(S / c m)$	6.12 × 10⁻⁴ at 25 wt.% ZnO	3.8 × 10⁻⁴ at 15 wt.% ZnO	4.2 × 10⁻⁵ at 10 wt.% ZnO	1.2 × 10^-4 at 20 wt% ZnO	Significantly higher conductivity due to optimized ZnO incorporation and interfacial interaction
Seebeck coefficient $(μ V / K)$	50 at 25 wt.% ZnO	Not reported	38 at 10 wt.% ZnO	26 at 15 wt.% ZnO	Higher thermoelectric efficiency with improved carrier transport mechanisms
Temperature range $(K)$	303–423	300–400	300–373	313–373	Broader temperature range studied, providing better insights into temperature-dependent properties
Structural insights	XRD confirmed consistent ZnO mixing with PANI and dual-phase morphology (platelet and granular structures)	Amorphous and partially crystalline phases observed	ZnO embedded with poor interfacial distribution	Crystalline nature but no dual-phase morphology reported	Advanced structural characterization revealed better filler dispersion and interlocking morphology
Application focus	Thermoelectric devices, temperature-dependent conductivity studies	Conductivity improvements for anticorrosion applications	Thermoelectric materials for energy harvesting	Electrical and mechanical property improvements for general-purpose applications	Broader application potential in thermoelectric devices with enhanced material properties

Conclusion

➢ Polyaniline and PANI-ZnO composites have been successfully synthesised by in-situ chemical polymerization methods and in-situ methods.

➢ The X-ray diffraction pattern confirmed that zinc-oxide nanoparticles are crystals, while pure polyaniline exhibits an amorphous nature. However, the PANI-ZnO composites pattern indicates a crystalline nature, suggesting a polyaniline interact with zinc oxide. The literature has reported on all the planes of zinc oxide.

➢ DC conductivity as a function of temperature $(303 K - 423 K)$ was conducted by KEITHELY 2400 source meter and studied in detailed which was not reported in literature. The studied sample showed good conductivity at temperature of $423 K$ , and maximum conductivity is observed for Polyaniline 25 wt.% Zinc-oxide. Here we observed Conductivity range at 0 wt.% is 1.43 $\times$ 10⁻⁴ $S / c m$ $\leq σ \leq$ 4.88 $\times$ 10⁻⁵ $S / c m$ at temperature range $(303 K - 423 K)$ , conductivity range at 20 wt% is 2.5 $\times$ 10⁻⁴ $S / c m$ $\leq σ \leq$ 2.3 $\times$ 10⁻⁵ $S / c m$ at temperature. Electrical properties were observed for Polyaniline and PANI-ZnO composites shows the semi-conductor (10⁻⁸ $S / c m$ -10³ $S / c m$ ) behavior in which conductivity increase with temperature, efficiency of charge transfer between the polymer chain and the dopant. Here we observed that activation energy about at 0 wt.% of composite is 5.419 $\times$ 10⁻⁵ $e V$ and at 25 wt.% of composite is 1.705 $\times$ 10⁻⁵ $e V$ . So, the activation energy of Polyaniline rapidly decreases by in increasing the concentration of the composite.

➢ Seebeck co-efficient measurement of PANI-ZnO composites also task this project which was not reported in literature. Nano-voltmeter $2182 A$ was used for observed voltage in mili volt or micro volt and slides were prepared by doctor-blade-method with copper contact. The Seebeck coefficient of Polyaniline composite are increased by increasing the concentration of Zinc oxide and its temperature range $(313 K - 373 K)$ as compare to purest form of Polyaniline. The Seebeck coefficient of all sample linearly raise by increasing the temperature and by increasing the concentration of Zinc oxide, and reaching the maximum 50 $μ V / K$ from 30 $μ V / K$ at 373 K. The reason is that dopant has wide band gap so most of carrier have energies above the Fermi level. Thermoelectric properties of the Polyaniline composite greatly improved than Polyaniline.

➢ The scanning electron micrographs (SEM) show dual phase, the platelet as well as the flaky structure, in PANI-ZnO.

Footnotes

ORCID iD

Muhammad Waheed Rasheed

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data Availability Statement

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.*

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