High Seebeck Coefficient Values Research Articles

Enhancing thermoelectric performance in flexible fabric-based Mo-doped CuAl2O4: Insights into carrier type modification and electrical conductivity optimization

In this work, we report the thermoelectric behaviour of flexible fabric-based Mo doped CuAl2O4. The doped Mo atom occupies the interstitial positions of the spinel lattice of CuAl2O4. This results the lattice expansion and also provides the carrier electrons. Initially, the pristine CuAl2O4 has the carrier concentration of 2.81 × 1014 cm−3, while doping with molybdenum, it not only increases the concentration of the carriers (about −7.65 × 1015 cm−3), but also changes the carrier type. The minimum doping (2 %) of molybdenum to spinel CuAl2O4 (CuAl2O4Mo0.02) creates the fermi level near to the conduction band, which reduces the band gap and results in the effective electrical conductivity as 0.69 Scm−1 at 340 K. The heavy doping enhances the scattering process. This leads to deduction of mobility and lower the electrical conductivity. The highest power factor of 0.0599 μWcm−1K−2 is achieved for the CuAl2O4Mo0.06 sample at 300 K. This is due to the high Seebeck coefficient value of the sample and has an ultralow thermal conductivity value of 0.056 W/mK. The highest output voltage of 3.9 mV is achieved for parallelly connected p-type CuAl2O4 -n-type CuAl2O4Mo0.02 thermoelectric device at the temperature difference of ΔT = 4.1 K. This research findings justify, the doping of molybdenum in the spinel lattice effectively enhances the thermoelectric properties of CuAl2O4 and provide the new ideas for the flexible, wearable fabric based thermoelectric research.

A first principles study of stability, electronic and thermoelectric characteristics of novel high temperature half- heusler alloys ScAgX (X=Si,Ge,Sn)

To meet the ever-increasing renewable energy demand Half- Heusler (HH) materials can be a potential candidate. Heusler materials are seeking popularity as efficient high-temperature thermoelectric materials. Here we systematically investigated the structural, electronic, mechanical and thermoelectric properties of novel HH compounds ScAgX (X = Si,Ge,Sn) in the framework of the first principles approach. These materials are found to be chemically, mechanically and dynamically stable. Born-Oppenheimer molecular dynamics simulations (BOMD) verify the thermal stability of these materials from 300 K to 1100 K. The semiconducting nature of these materials is confirmed by the electronic band structure. ScAgX (X = Si,Ge,Sn) have an indirect band gap of 0.37 eV, 0.42 eV and 0.38 eV respectively. A high value of Seebeck coefficient of 6351 μV/K, 6955 μV/K and 6558 μV/K has been obtained at room temperature. ScAgSi shows a high value of electrical conductivity (∼106 S/m) among these compounds at room temperature. The calculated value of the figure of merit (ZT) of ScAgX (X = Si,Ge,Sn) is 0.12, 0.08 and 0.16 at 1100 K respectively. Our present investigation shows that these materials can be a potential candidate for high-temperature thermoelectric power generation.

Thermoelectric performance of newly discovered LiHfPdZ (Z= Al, Ga, and In) quaternary Heusler compounds: A DFT study

Li-based quaternary Heusler LiHfPdZ (Z = Al, Ga, and In) compounds have been investigated for their electronic properties, structural stability, phonon spectra, and thermoelectric performance. Band structure calculations based on Density Functional Theory, show the indirect semiconductor nature of LiHfPdZ (Z = Al, Ga, and In) compounds with band gaps of 0.73 eV, 0.79 eV, and 0.58 eV, respectively. We obtained flat Hf-5d bands (without dispersion) in the vicinity of Fermi energy (EF), resulting in a high value of Seebeck coefficient. The positive values of frequencies in the phonon dispersion curve confirm the dynamic stability of these compounds. The computed elastic properties suggested that the studied compounds are mechanically stable. The calculated values of melting points of this compounds are around 1500 ± 300 K, which ensures the stability of these compounds at high temperatures. We obtained a maximum value of the figure of merit 0.72, 0.68 and 0.67 for LiHfPdAl, LiHfPdGa and LiHfPdIn compounds respectively, which is higher than other Li based QH compounds of same kind i.e. LiHfCoSn (0.59) and LiHfCoGe (0.61) obtained by Singh et al. at same temperature. Overall, a comparatively high and stable value of ZT above 600 K is obtained only in LiHfPdAl, which suggests that it is the most suitable candidate as TE material for high-temperature applications.

Flexible thermoelectrics in crossed graphene/hBN composites

Nanostructures exhibit unusual properties due to the dominance of quantum mechanical effects. In addition, the geometry of a nanostructure can have a strong influence on its physical properties. Using the tight-binding and force-constant approaches with the help of the non-equilibrium Green’s function method, the transport and thermoelectric properties of cross-shaped (X-shaped) composite heterostructures are studied in two cases: Mixed graphene and h-BN (HETX-CBN) and all graphene (HETX-C) cross-shaped structures. Our numerical results show that an X-shaped structure helps to manipulate its electronic and phononic properties. The transport energy gap can be tuned in the range of ~ 0.8 eV by changing one arm width. Due to the drastic decrease in the electronic conductance of HETX-CBN and the dominance of the phononic thermal conductance, the ZT performance is degraded despite the high Seebeck coefficient value (in the order of meV). However, HETX-C has better ZT performance due to better electronic conductance and lower phononic/electronic thermal ratio, it can enhance the ZT ~ 2.5 times compared to that of zigzag graphene nanoribbon. The thermoelectric properties of the system can be tuned by controlling the size of the arms of the device and the type of its atoms.

PREPARATION AND THERMOELECTRIC PROPERTIES OF p-TYPE Ag(1-x)Cu(1+x)Te SAMPLES BY SPARK PLASMA SINTERING METHOD

The combination of silver (Ag), copper (Cu), and telluride (Te) yields silver copper telluride (AgCuTe), a new type of ternary liquid-like thermoelectric material. Due to its ultra-low lattice thermal conductivity and highly symmetrical cubic crystal structure, it exhibits excellent thermoelectric properties in the medium-to-high temperature range (400-600 K). However, hexagonal crystal structures with lower symmetry near room temperature can lead to higher thermal conductivity. In addition, the high carrier concentration of the hexagonal crystal structure results in a lower Seebeck coefficient for the material. This seriously affects the application of AgCuTe-based thermoelectric materials in the room temperature range. Therefore, how to improve the thermoelectric performance of AgCuTe-based thermoelectric materials in the room temperature range has received widespread attention from researchers. AgCuTe-based thermoelectric materials were successfully prepared by mechanically alloying Ag, Cu, and Te powders using a planetary ball mill combined with spark plasma sintering. On this basis, the thermoelectric properties of AgCuTe-based materials were optimized by adjusting the Ag/Cu ratio and Ag<sub>2</sub>Te/CuTe content. The results indicated that at 600 K, the Ag<sub>0.93</sub>Cu<sub>1.07</sub>Te sample obtained a high Seebeck coefficient value of approximately 171 μV/K<sup>-1</sup>. Finally, the ZT peak obtained from the Ag<sub>093</sub>Cu<sub>1.07</sub>Te sample was 1.06; compared with AgCuTe (ZT = 0.78), it had increased by about 36%.

Production of (Fe,Co)Si2 and (Fe.Mn)Si2 Thermoelectric Materials by Spark Plasma Sintering

In this study, FeSi2 bulk specimens were prepared by mechanical alloying, spark plasma sintering, and subsequent annealing. The annealed FeSi2 bulk specimens consisted of the β-FeSi2 phase and exhibited high Seebeck coefficient values. The maximum Seebeck coefficient of 356 μVK−1 was achieved in the FeSi2 bulk specimen annealed at 1173 K for 6 h. However, the power factor of the FeSi2 bulk specimen was quite small due to its high electrical resistivity, and a drastic improvement is required. Therefore, Mn- and Co-substituted specimens, Fe1−xMnxSi2 (x = 0.2–0.8) and Fe1−xCoxSi2 (x = 0.2–0.8), were produced, and their thermoelectric properties were evaluated. The Mn- and Co-substituted specimens exhibited lower electrical resistivity and a higher power factor than the FeSi2 bulk specimen. The Fe1−xMnxSi2 (x = 0.2–0.8) bulk specimens were p-type thermoelectric materials, and a Seebeck coefficient of 262 μVK−1 and a power factor of 339 μWm−1K−2 were achieved in the Fe0.94Mn0.06Si2 bulk specimen. On the other hand, the Fe1−xCoxSi2 (x = 0.2–0.8) bulk specimens were n-type thermoelectric materials, and a Seebeck coefficient of −180 μVK−1 and a power factor of 667 μWm−1K−2 were achieved in the Fe0.96Co0.04Si2 bulk specimen.

Electrical and thermoelectrical properties of Bi2−xNaxTe3 alloys

For the first time, Bi 2 Te 3 alloys, which have long been known as promising thermoelectric materials for room temperature applications, have been doped with Na atoms to enhance their thermoelectric performance. Bi 2 Te 3 and Bi 2−x Na x Te 3 alloys were prepared by mono-temperature melting synthesis. Their structural, crystallographic properties and surface morphology were investigated by XRD and SEM analyses. All the prepared alloys showed perfect crystalline structure of single Bi 2−x Na x Te 3 phase. The thermoelectric properties of the synthesized alloys were measured in the temperature range of 273–473 K. Electrical conductivity of the concerned alloys were measured by the standard four probe method and studied as a function of temperature, showing metal-like behavior. Na-doping enhanced the electrical conductivity significantly due to enhancing of the carrier concentration. The Seebeck coefficient of all alloys exhibited a positive sign, confirming the p-type conduction. Significantly high Seebeck coefficient values were observed at high temperatures. The maximum value was recorded at 266 μV K − 1 for Bi 2 Te 3 at 473 K. Electronic thermal conductivity of the prepared alloys was estimated from Wiedemann-Franz equation. A remarkable reduction of the electronic thermal conductivity was observed against temperature, in correspondence with the electrical conductivity. The materials thermoelectric power factor was calculated based on electrical conductivity and Seebeck coefficient measurements. Also, the power factor was investigated as a function of temperature. The largest value was found for the most Na-doped samples at 299.6 µW/mK 2 , observed at 413 K. • Bi 2 Te 3 and Bi 2−x Na x Te 3 alloys were prepared by mono-temperature melting synthesis. • Thermoelectric measurements were carried out in the temperature range 273–473 K. • The maximum power factor was observed at 299.6 µW/mK 2 , observed at 413 K.

First principles calculations to investigate Li-based quaternary Heusler compounds LiHfCoX (X = Ge, Sn) for thermoelectric applications

In the last few decades, varieties of semiconductors have been explored for electronic and thermoelectric applications. As a result of these motivations, the current research work investigates the structural, electronic, vibrational, elastic, mechanical, thermodynamic, and thermoelectric properties of two quaternary Heuslers (QHs), namely LiHfCoGe and LiHfCoSn (both of which are semiconducting in nature), within the computational framework of DensityFunctional Theory (DFT) and Boltzmann transport equations. Both alloys display the p-type semiconductivity, dynamical stability and crystallize in the FCC cubic structure within F-43 m space group. The high Seebeck coefficient values pronounce an excellent and fundamental thermoelectric character. The large melting points expose their scope in the high-temperature regions. However, all of the thermoelectric characteristics are also measured in terms of the estimated relaxation time using deformation potential theory. Even though the figure of merit (ZT) is in the middle of the pack yet better than many compounds of the same sort. The impact of spin–orbit coupling on the thermoelectric characteristics is also examined. The practical utilization of the materials can be evaluated from the elastic and mechanical properties that are favorable in manufacturing efficient and reliable Thermoelectric Modules at high-temperatures.

The Influence of Ti Doping at the Mn Site on Magnetoresistance and Thermopower Properties of Nd-=SUB=-0.5-=/SUB=-Ca-=SUB=-0.5-=/SUB=-MnO-=SUB=-3-=/SUB=-

Nd-Ca-based manganite Nd0.5Ca0.5MnO3 and 10% Ti-doped manganite Nd0.5Ca0.5Ti0.1Mn0.9O3 denoted by N and N0.1, respectively, were prepared using solid-state reaction method. Resistivity gets increased for the Ti-doped sample. The parent compound N has remarkably high magnetoresistance. The highest value of Seebeck coefficient for N is -97 μVK-1 at 143 K and for N0.1 is -207 μVK-1 at 203 K. Variable range hopping mechanism successfully explains the high temperature resistivity and thermopower data. Keywords: magnetoresistance, thermoelectric power, rare-earth based manganites, manganites.

Physical properties of double perovskites Rb2XCl6 (X= Sn, Te, Zr): Competitive candidates for renewable energy devices

Ab-initio computations are performed to analyze the Lead-free double perovskites Rb2XCl6 (X = Sn, Te, Zr) for solar cells and renewable energy. The FP-LAPW method has been adopted to compute the mechanical, optoelectronic and thermoelectric properties. The stability of the three compounds is verified through the elastic constants ensuring the ductility and the anisotropic nature of the double perovskites compounds. Both compounds Rb2TeCl6 and Rb2ZrCl6 have indirect band gap equal 2.54 eV, 3.46 eV respectively, but Rb2SnCl6 compound have direct band gap equal to 2.40 eV in the near visible region, which make them potential candidates for visible light solar cells. The optical spectra have been elaborated in terms of dielectric constants, absorption of light, refractive index, and reflection of light. The maximum absorption bands are recorded in the wavelength range of 620 nm–310 nm. Finally, thermoelectric properties are calculated by BoltzTraP code, which depicts high values of Seebeck coefficient and low thermal conductivity. Therefore, the above said parameters ensure their importance for renewable energy.

Ab-initio study of lead-free double Perovskites Cs2AgZBr6 (Z = Bi, Sb) for Solar cells and other renewable energy applications

Ab-initio computations are performed to analyze the Lead-free double perovskites Cs2AgZBr6 (Z ​= ​Bi, Sb)for solar cells and renewable energy. Modified Becke and Johnson potential (TB-mBJ) has been adopted to compute the electronic and optical properties. The computed lattice constants are found in good agreement with the reported experimental data. Band gaps calculations for Cs2AgBiBr6 and Cs2AgSbBr6 reveal their indirect nature and are quantified 2.0 ​eV and 1.39 ​eV which make them potential candidates for visible light solar cells. The optical spectra have been elaborated in terms of dielectric constants, absorption of light, refractive index, and reflection of light. The maximum absorption bands are recorded in the wavelength range of 620 ​nm–310 ​nm. Finally, thermoelectric properties are calculated by BoltzTraP code, which depicts high values of Seebeck coefficient and low thermal conductivity. Thus, performed theoretical calculations suggest the studied materials for potential application in renewable energy field.

Effect of cation exchange on structural, electronic, magnetic and transport properties of Ba2MReO6 (M = In, Gd)

Insight on the structural, electronic, magnetic and thermoelectric properties of Ba2MReO6 (M = In, Gd) compounds has been taken into the examination under density functional theory approach. Formation energy (ΔHf) calculation resulted in −53.60 eV (Ba2InReO6) and −58.09 eV (Ba2GdReO6) which specify that the given compounds are thermodynamically stable. Tolerance factors (τ) of about a unity (0.9) for both materials clarify their cubic stability while high values of cohesive energies have explored strong bonds between the constituent atoms. Structural optimizations support the ferromagnetic stability of both materials with the lattice constants values of 8.20 Å (Ba2InReO6) and 8.37 Å (Ba2GdReO6). The spin-based density of states calculations described the half metallicity in both the compounds, where, in spin down state, the semiconducting nature with direct band gap of 2.94 eV and 2.74 eV for Ba2InReO6 and Ba2GdReO6 respectively was evaluated from band structure calculation. Total magnetic moments equal to 2.00 μB (Ba2InReO6) and 9.00 μB (Ba2GdReO6) pose strong ferromagnetism in them. The calculated thermoelectric coefficients support the high electrical and low electronic thermal conductivities and suggest the efficient functioning of the studied compounds at wide range of temperatures (200 K-800 K). Also, high values of Seebeck coefficient (S) and figure of merit (ZT) pretenses their applications for thermoelectric conversions. The overall properties via these first principle calculations opens the possibilities of Ba2MReO6 for their future experimental perceptions with exciting applications in spintronics and green power generation.

Thermoelectric Properties of SnO<sub>2</sub>/Bi<sub>2</sub>Te<sub>3</sub> Composite

In this study, SnO2 nanoparticles of wt% 2, 4, 6, and 8 were uniformly composite in Bi2Te3 matrix. SnO2 nanoparticle was synthesized using co-precipitation method. The result shows that based on XRD and EDS analysis the composites do not contain any impurities. The thermoelectric properties of the composites strongly depend on the Seebeck coefficient. The highest value of Seebeck coefficient of -177 µV/K is obtained at around 375 K for the 4% SnO2/Bi2Te3 sample. This yields the highest value of the power factor of 4.0 × 10-3 Wm-1K-1 compared to the pure Bi2Te3 synthesized using the same procedure by 14.3%. This result demonstrates that the thermoelectric properties of Bi2Te3 can be improved using oxide nanoparticles.

Comparative study of functionalized MXenes Mn+1CnO2 (M = Ti, Zr and Hf, n = 1, 2 and 3): A proposal for renewable energy applications

Using first-principles calculations, we studied the electronic, structural and thermoelectric properties of two-dimensional (2D) MXenes [Formula: see text] ([Formula: see text] = Ti, Zr and Hf, [Formula: see text], 2 and 3). The calculations are carried out within the generalized gradient approximation (GGA). We have calculated the Boltzmann transport equation for finding the thermoelectric properties such as power factor, Seebeck coefficient and electrical conductivity. For [Formula: see text], these materials behave as semiconductors having an indirect bandgap nature. In contrast, for [Formula: see text] these materials show metallic behavior. Out of these MXenes, we found that Ti2CO2 has a high Seebeck coefficient value, whereas the electrical conductivity of Ti4C3O2 is exceptionally high. While among all these compounds, Ti2CO2 and Hf4C3O2 have a high power factor in the 300–1200-K temperature range.

Electronic and thermoelectric properties of natural layered structural compounds SrCuChF (Ch=S, Se and Te)

In this paper, we study the crystal structures, density of states, electronic band structures and thermoelectric transport properties of SrCuChF (Ch = S, Se and Te) by the way of the first principle. The pictures of electronic band structure show the relatively large dispersion near the maximum value of valence band in the directions of Γ-M and Γ-X, but in the direction of Γ-Z, the band structure is relatively flat, and the top of valence band is mainly composed of Cu-Ch anti-bond state which has a very significant impact on the transport performance of p-type SrCuChF. Base on the semiclassical Boltzmann transport theory, we find that the p-type SrCuChF has a high value of Seebeck coefficient due to the quasi-flat character of the electronic bands at the edges of the valence band, and the outstanding anisotropic properties due to their natural layered structure. According to the predicted maximum value of power factors, the optimal doping concentration is presented. Therefore, we give a natural layered structure complex SrCuChF with the good thermoelectric properties and may find many important applications in the thermoelectric functional materials.

Defective perovskites Cs2SeCl6 and Cs2TeCl6 as novel high temperature potential thermoelectric materials

On basis of our first principle calculations, we suggest lead free defective perovskites Cs2SeCl6 and Cs2TeCl6 as efficient high temperature thermoelectric materials. Our calculations predict high stability of these materials. The calculated flat valence bands in these compounds results high values of Seebeck coefficient. The density of states predicts the p-type conductivity in both compounds which was confirmed from positive value of Seebeck coefficient. The calculated thermal conductivity was found as low, 1.068 and 0.697 W/mK for Cs2SeCl6 and Cs2TeCl6, respectively at 800 K. This results high ZT values in comparison of lead halide perovskites. The combination of high electrical conductivity with Seebeck coefficient give rise to reasonable values of power factor 0.81 × 10−3 W/mK2 for Cs2SeCl6 and 0.83 × 10−3 W/mK2 for Cs2TeCl6 at 800 K. Furthermore, our calculated mechanical properties predicted the studied compounds as ductile. The ductile nature along with high values of thermoelectric parameters makes Cs2SeCl6 and Cs2TeCl6 compounds more promising for thermoelectric power generation at high temperatures.

Comparison of Thermoelectric Properties of ZnO and ZnSnO Thin Films Grown on Si Substrate by Thermal Evaporation

In this manuscript, we compared the thermoelectric properties of ZnO and ZnSnO thin films grown on silicon (100) substrate. We have evaporated Zn and Sn+Zn metal powders were evaporated in vacuum tube furnace alternatively, under same experimental conditions for the growth of ZnO and ZTO respectively. After the deposition, these grown films were cut into pieces and post growth annealed at different annealing temperatures from 600oC to 800oC in the air using programmable muffle furnace. Seebeck and Hall data suggested that ZTO sample shows highest value of Seebeck coefficient, electrical conductivity and power factor as compared to the ZnO samples. It is also observed that the value of Seebeck coefficient showing an increasing trend for both of the samples as we increase the post growth annealing temperature. The higher thermoelectric properties for ZTO are due the presence of Sn atoms in ZnO structure. Tin dopants may generate secondary phases and/or enhanced the carrier mobility which might be the reason that ZTO has improved thermo-electric properties as compared to ZnO. XRD and Raman measurements were used to confirm the formation of ZTO. XRD data verified the hexagonal structure of ZnO but a slight red shift is observed for the case of ZTO samples. To further justify our argument, we have also performed Raman spectroscopy measurements which confirmed the presence of Sn elements in ZTO.

Structural, thermo-elastic, electro-magnetic and thermoelectric attributes of quaternary CoNbMnX (X = Al, Si) Heusler alloys

This investigation consists of performing the structural, thermodynamic, electronic, magnetic and thermoelectric characteristics of the quaternary Heusler CoNbMnX (X = Al, Si) alloys using DFT within Wien2k code. Our calculations show that the atomic arrangement of the two alloys CoNbMnAl and CoNbMnSi is Type-I. From the elastic constant and the formation energy values, these compounds are predicted to be mechanically and thermodynamically stable, thus can be formed experimentally. The calculated values of their bulk modulus and cohesive energy values show that CoNbMnSi is more rigid than CoNbMnAl. From the analysis of the electronic properties, CoNbMnAl is identified to be paramagnetic and semiconductor alloy with 0.15 eV narrow indirect (Γ-X) band gap. Whereas, CoNbMnSi is characterized as a ferromagnetic alloy with half-metallicity character having a total magnetic moment of 1μB. The charge density contours and Fermi surface, predict a combined covalent and ionic bond between the atoms of CoNbMnX alloys. The calculated thermoelectric parameters assume that these alloys tend to behave as p-type with the same thermoelectric efficiency for either charge carriers; hole or electron. Depending on the high Seebeck coefficient value and ZT = 1 of the present alloys, potential applications are predicted, such as spin injection materials and spintronic applications.

Theoretical study of the phase transitions and electronic structure of (Zr0.5, Mg0.5)N and (Hf0.5, Mg0.5)N

Rock-salt scandium nitride has gained interest due to its thermoelectric properties including a relatively high Seebeck coefficient. This motivates research for other semiconductor materials that exhibit similar electronic structure features as ScN. Using density functional theory calculations, we have studied disordered solid solutions of (Zr0.5, Mg0.5)N and (Hf0.5, Mg0.5)N using the special quasi-random structure model. The results show that within a mean-field approximation for the configurational entropy, the order–disorder phase transformation between the monoclinic LiUN2 prototype structure and the rock-salt cubic random alloy of these mentioned solid solutions occur at 740 K and 1005 K for (Zr0.5, Mg0.5)N and (Hf0.5, Mg0.5)N, respectively. The density-of-states for the two ternary compounds is also calculated and predicts semiconducting behavior with band gaps of 0.75 eV for (Zr0.5, Mg0.5)N and 0.92 eV for (Hf0.5, Mg0.5)N. The thermoelectric properties of both compounds are also predicted. We find that in the range of a moderate change in the Fermi level, a high Seebeck coefficient value at room temperature can be achieved.

Effect of annealing temperature on thermoelectric properties of zinc nitride thin films grown by thermal evaporation method

In this manuscript, we have successfully grown the Zinc Nitride (Zn3N2) thin films for thermoelectric power generation applications using thermal evaporation method. Zinc powder (0.1 g) was evaporated in vacuum tube furnace on the glass substrate having boot temperature of 830 °C under the nitrogen flow rate of 120 sccm. In order to study the annealing effect, one of samples was annealed at 350 °C using programmable muffle furnace. X-ray diffraction data (XRD) of as grown sample confirm the formation of Zn3N2 phase while the post annealing resulted in degradation of crystallinity of film. SEM images show the granular morphology, which starts to diffuse upon annealing. Seebeck data has demonstrated the highest value of Seebeck coefficient for as grown sample (142 μV/°C) which reduces to 52 μV/°C upon annealing. This reduction in Seebeck coefficient was associated with the degradation of crystallinity by post annealing which causes in reduction of the mobility of carriers. Electrical conductivity data show the similar decreasing trend from 83 to 42 S/cm as a result of post annealing. So, overall highest value of Seebeck coefficient and electrical conductivity of un-annealed sample leads to the highest power factor of 1.67 × 10-4 Wm-1K-2.