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

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 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>303</mml:mn> <mml:mo> </mml:mo> <mml:mi>K</mml:mi> <mml:mo> </mml:mo> <mml:mi>t</mml:mi> <mml:mi>o</mml:mi> <mml:mo> </mml:mo> <mml:mn>423</mml:mn> <mml:mo> </mml:mo> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> ). At 0 wt.%, the conductivity ranged from 4.88 × 10 −5 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>S</mml:mi> <mml:mo>/</mml:mo> <mml:mi>c</mml:mi> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>303</mml:mn> <mml:mo> </mml:mo> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> to 1.43 × 10 −4 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>S</mml:mi> <mml:mo>/</mml:mo> <mml:mi>c</mml:mi> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>423</mml:mn> <mml:mo> </mml:mo> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> . For the 20 wt.% composite, the values were 2.3 × 10 −6 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>S</mml:mi> <mml:mo>/</mml:mo> <mml:mi>c</mml:mi> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> at 303 K and 2.5 × 10 −4 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>S</mml:mi> <mml:mo>/</mml:mo> <mml:mi>c</mml:mi> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>423</mml:mn> <mml:mo> </mml:mo> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> . Notably, the 25 wt.% composite exhibited enhanced conductivity, reaching 6.12 × 10 −4 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>S</mml:mi> <mml:mo>/</mml:mo> <mml:mi>c</mml:mi> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>423</mml:mn> <mml:mo> </mml:mo> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> and 1.0 × 10 −7 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>S</mml:mi> <mml:mo>/</mml:mo> <mml:mi>c</mml:mi> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>303</mml:mn> <mml:mo> </mml:mo> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> . 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>V</mml:mi> <mml:mo>/</mml:mo> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> from 30 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>V</mml:mi> <mml:mo>/</mml:mo> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>373</mml:mn> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> , 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.