Role of cobalt doping on the electrical conductivity of ZnO nanoparticles

Godavarti, Umadevi; Mote, V. D.; Dasari, Madhavaprasad

doi:10.1016/j.jascer.2017.08.002

Cited by 95 publications

(25 citation statements)

References 33 publications

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“…Conductivity of nanoparticles depends upon grain size, morphology, and microstructure and it is ca. 1.5 × 10 −7 S/cm [ 59 ]. Because of the low volume fraction of ZnO NPs in CS-ZnO films (from 0 to 0.15 wt.%; see below the volume fraction calculation), the effective conductivity of nanocomposites practically depends upon the conductivity of neat CS ( ca .…”

Section: Discussionmentioning

confidence: 99%

Chitosan-ZnO Nanocomposites Assessed by Dielectric, Mechanical, and Piezoelectric Properties

et al. 2020

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The aim of this work is to structurally characterize chitosan-zinc oxide nanoparticles (CS-ZnO NPs) films in a wide range of NPs concentration (0–20 wt.%). Dielectric, conductivity, mechanical, and piezoelectric properties are assessed by using thermogravimetry, FTIR, XRD, mechanical, and dielectric spectroscopy measurements. These analyses reveal that the dielectric constant, Young’s modulus, and piezoelectric constant (d33) exhibit a strong dependence on nanoparticle concentration such that maximum values of referred properties are obtained at 15 wt.% of ZnO NPs. The piezoelectric coefficient d33 in CS-ZnO nanocomposite films with 15 wt.% of NPs (d33 = 65.9 pC/N) is higher than most of polymer-ZnO nanocomposites because of the synergistic effect of piezoelectricity of NPs, elastic properties of CS, and optimum NPs concentration. A three-phase model is used to include the chitosan matrix, ZnO NPs, and interfacial layer with dielectric constant higher than that of neat chitosan and ZnO. This layer between nanoparticles and matrix is due to strong interactions between chitosan’s side groups with ZnO NPs. The understanding of nanoscale properties of CS-ZnO nanocomposites is important in the development of biocompatible sensors, actuators, nanogenerators for flexible electronics and biomedical applications.

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Section: Discussionmentioning

confidence: 99%

Chitosan-ZnO Nanocomposites Assessed by Dielectric, Mechanical, and Piezoelectric Properties

et al. 2020

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“…The grain size reduced with increase of cobalt doping concentration whereas it forms densely packed network. It is clearly observed that for increase in cobalt concentration from 1% to 7% the grain size was found to be decreased [33,34] according to the figures 3(d), (e). Here it was noticed that the dopant deteriorate the degree of crystallization through its substitution.…”

Section: Surface Morphologymentioning

confidence: 76%

Structural and magnetic properties of cobalt doped ZnO thin films deposited by cost effective nebulizer spray pyrolysis technique

Abirami¹,

Arulanantham²,

Wilson³

2020

Mater. Res. Express

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In this work, we report the structural, optical and magnetic properties of Co doped ZnO thin films fabricated by nebulizer spray pyrolysis technique. Five different thin films were fabricated with various doping concentration of cobalt. These thin films posses hexagonal wurtzite structure with polycrystalline nature and strongly oriented along with (002) and (101) direction. From x-ray diffraction pattern, average crystallite sizes were calculated and are found to be decreases with Co doping concentration. The dislocation density and microstrain values of the coated films increased gradually with doping concentration. The SEM/AFM studies reveal the change from spherical shape to petal shaped grains and it is also found that the size of grains and roughness decreases with Co increasing doping concentration. The lowering of the optical band gap energy from ∼ 3.24 eV to 3.05 eV shows doping by Co in ZnO gives rise to band gap bowing in ZnO:Co thin films. The M-H curve confirms the god ferromagnetism in Co doped ZnO thin films.

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“…It should be noticed that the pristine ZnO with a wurtzite structure is a natural n-type semiconductor, provided by the deviations from stoichiometry and presence of intrinsic defects like oxygen vacancies and zinc interstitials [6]. The nonlinear log σ vs. T −1 behaviour was also observed for other donor-doped ZnO-based materials [31,32], and attributed to the temperature dependence of the contributions provided by the thermal excitation of electrons from donor levels to the conduction band, hopping between the impurity bands, oxygen vacancies, zinc interstitials and oxygen sorption–desorption processes to the overall charge transport mechanism. The activation energies for both high and low-temperature ranges (Table 1) significantly decrease for the doped materials as compared to the pristine ZnO, likely due to the electron donor effect.…”

Section: Resultsmentioning

confidence: 99%

Exploring Tantalum as a Potential Dopant to Promote the Thermoelectric Performance of Zinc Oxide

et al. 2019

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Zinc oxide (ZnO) has being recognised as a potentially interesting thermoelectric material, allowing flexible tuning of the electrical properties by donor doping. This work focuses on the assessment of tantalum doping effects on the relevant structural, microstructural, optical and thermoelectric properties of ZnO. Processing of the samples with a nominal composition Zn1−xTaxO by conventional solid-state route results in limited solubility of Ta in the wurtzite structure. Electronic doping is accompanied by the formation of other defects and dislocations as a compensation mechanism and simultaneous segregation of ZnTa2O6 at the grain boundaries. Highly defective structure and partial blocking of the grain boundaries suppress the electrical transport, while the evolution of Seebeck coefficient and band gap suggest that the charge carrier concentration continuously increases from x = 0 to 0.008. Thermal conductivity is almost not affected by the tantalum content. The highest ZT~0.07 at 1175 K observed for Zn0.998Ta0.002O is mainly provided by high Seebeck coefficient (−464 V/K) along with a moderate electrical conductivity of ~13 S/cm. The results suggest that tantalum may represent a suitable dopant for thermoelectric zinc oxide, but this requires the application of specific processing methods and compositional design to enhance the solubility of Ta in wurtzite lattice.

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Role of cobalt doping on the electrical conductivity of ZnO nanoparticles

Cited by 95 publications

References 33 publications

Chitosan-ZnO Nanocomposites Assessed by Dielectric, Mechanical, and Piezoelectric Properties

Chitosan-ZnO Nanocomposites Assessed by Dielectric, Mechanical, and Piezoelectric Properties

Structural and magnetic properties of cobalt doped ZnO thin films deposited by cost effective nebulizer spray pyrolysis technique

Exploring Tantalum as a Potential Dopant to Promote the Thermoelectric Performance of Zinc Oxide

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