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Lithium ionic conduction and relaxation dynamics of spark plasma sintered Li5La3Ta2O12 garnet nanoceramics.

Ahmad MM - Nanoscale Res Lett (2015)

Bottom Line: The grain size of the SPS nanoceramics is in the 50 to 100 nm range, indicating minimal grain growth during the SPS experiments.Interestingly, we found that only a small fraction of lithium ions of 3.9% out of the total lithium content are mobile and contribute to the conduction process.Moreover, the relaxation dynamics in the investigated materials have been studied through the electric modulus formalism.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, College of Science, King Faisal University, Hofuf, Al-Ahsaa, 31982 Saudi Arabia ; Physics Department, Faculty of Science, Assiut University in The New Valley, El-Kharga, The New Valley, 72511 Egypt.

ABSTRACT
In the present work, nanoceramics of Li5La3Ta2O12 (LLT) lithium ion conductors with the garnet-like structure are fabricated by spark plasma sintering (SPS) technique at different temperatures of 850°C, 875°C, and 900°C (SPS-850, SPS-875, and SPS-900). The grain size of the SPS nanoceramics is in the 50 to 100 nm range, indicating minimal grain growth during the SPS experiments. The ionic conduction and relaxation properties of the current garnets are studied by impedance spectroscopy (IS) measurements. The SPS-875 garnets exhibit the highest total Li ionic conductivity of 1.25 × 10(-6) S/cm at RT, which is in the same range as the LLT garnets prepared by conventional sintering technique. The high conductivity of SPS-875 sample is due to the enhanced mobility of Li ions by one order of magnitude compared to SPS-850 and SPS-900 ceramics. The concentration of mobile Li(+) ions, n c, and their mobility are estimated from the analysis of the conductivity spectra at different temperatures. n c is found to be independent of temperature for the SPS nanoceramics, which implies that the conduction process is controlled by the Li(+) mobility. Interestingly, we found that only a small fraction of lithium ions of 3.9% out of the total lithium content are mobile and contribute to the conduction process. Moreover, the relaxation dynamics in the investigated materials have been studied through the electric modulus formalism.

No MeSH data available.


Scaling of the modulus spectra for all SPS garnet nanoceramics at different temperatures.
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Fig11: Scaling of the modulus spectra for all SPS garnet nanoceramics at different temperatures.

Mentions: The modulus scaling of the investigated SPS garnets have been performed using and fmax as the scaling parameters of the M′ and the frequency axes, respectively. The results of the scaling processes at different temperatures for the SPS LLT ceramics are shown in Figure 10. The modulus spectra at different temperatures are superimposed into a single master curve for each sample, indicating that the relaxation process is independent of temperature. The full width at half maximum (FWHM) has similar values of 1.77 decades for the SPS-850, SPS-875, and SPS-900 nanoceramics. These values are larger than that of the ideal Debye relaxation (FWHM of 1.14 decades, ref. [37]), which suggests a distribution of relaxation times due to disordering nature in the current lithium garnet nanoceramics. Scaling of the modulus spectra of the different SPS ceramics together at different temperatures is shown in Figure 11. This figure shows that the modulus spectra of all the samples are merged into a single master curve, implying that the studied materials exhibit similar relaxation processes.Figure 10


Lithium ionic conduction and relaxation dynamics of spark plasma sintered Li5La3Ta2O12 garnet nanoceramics.

Ahmad MM - Nanoscale Res Lett (2015)

Scaling of the modulus spectra for all SPS garnet nanoceramics at different temperatures.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385244&req=5

Fig11: Scaling of the modulus spectra for all SPS garnet nanoceramics at different temperatures.
Mentions: The modulus scaling of the investigated SPS garnets have been performed using and fmax as the scaling parameters of the M′ and the frequency axes, respectively. The results of the scaling processes at different temperatures for the SPS LLT ceramics are shown in Figure 10. The modulus spectra at different temperatures are superimposed into a single master curve for each sample, indicating that the relaxation process is independent of temperature. The full width at half maximum (FWHM) has similar values of 1.77 decades for the SPS-850, SPS-875, and SPS-900 nanoceramics. These values are larger than that of the ideal Debye relaxation (FWHM of 1.14 decades, ref. [37]), which suggests a distribution of relaxation times due to disordering nature in the current lithium garnet nanoceramics. Scaling of the modulus spectra of the different SPS ceramics together at different temperatures is shown in Figure 11. This figure shows that the modulus spectra of all the samples are merged into a single master curve, implying that the studied materials exhibit similar relaxation processes.Figure 10

Bottom Line: The grain size of the SPS nanoceramics is in the 50 to 100 nm range, indicating minimal grain growth during the SPS experiments.Interestingly, we found that only a small fraction of lithium ions of 3.9% out of the total lithium content are mobile and contribute to the conduction process.Moreover, the relaxation dynamics in the investigated materials have been studied through the electric modulus formalism.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, College of Science, King Faisal University, Hofuf, Al-Ahsaa, 31982 Saudi Arabia ; Physics Department, Faculty of Science, Assiut University in The New Valley, El-Kharga, The New Valley, 72511 Egypt.

ABSTRACT
In the present work, nanoceramics of Li5La3Ta2O12 (LLT) lithium ion conductors with the garnet-like structure are fabricated by spark plasma sintering (SPS) technique at different temperatures of 850°C, 875°C, and 900°C (SPS-850, SPS-875, and SPS-900). The grain size of the SPS nanoceramics is in the 50 to 100 nm range, indicating minimal grain growth during the SPS experiments. The ionic conduction and relaxation properties of the current garnets are studied by impedance spectroscopy (IS) measurements. The SPS-875 garnets exhibit the highest total Li ionic conductivity of 1.25 × 10(-6) S/cm at RT, which is in the same range as the LLT garnets prepared by conventional sintering technique. The high conductivity of SPS-875 sample is due to the enhanced mobility of Li ions by one order of magnitude compared to SPS-850 and SPS-900 ceramics. The concentration of mobile Li(+) ions, n c, and their mobility are estimated from the analysis of the conductivity spectra at different temperatures. n c is found to be independent of temperature for the SPS nanoceramics, which implies that the conduction process is controlled by the Li(+) mobility. Interestingly, we found that only a small fraction of lithium ions of 3.9% out of the total lithium content are mobile and contribute to the conduction process. Moreover, the relaxation dynamics in the investigated materials have been studied through the electric modulus formalism.

No MeSH data available.