Dutta, Moinak ; Sanyal, Dirtha ; Biswas, Kanishka (2018) Tuning of p–n–p-Type Conduction in AgCuS through Cation Vacancy: Thermopower and Positron Annihilation Spectroscopy Investigations Inorganic Chemistry, 57 (12). pp. 7481-7489. ISSN 0020-1669
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Official URL: http://doi.org/10.1021/acs.inorgchem.8b01246
Related URL: http://dx.doi.org/10.1021/acs.inorgchem.8b01246
Abstract
Understanding the complex phenomenon behind the structural transformations is a key requisite to developing important solid-state materials with better efficacy such as transistors, resistive switches, thermoelectrics, etc. AgCuS, a superionic semiconductor, exhibits temperature-dependent p–n–p-type conduction switching and a colossal jump in thermopower during an orthorhombic to hexagonal superionic transition. Tuning of p–n–p-type conduction switching in superionic compounds is fundamentally important to realize the correlation between electronic/phonon dispersion modulation with changes in the crystal structure and bonding, which might contribute to the design of better thermoelectric materials. Herein, we have created extrinsic Ag/Cu nonstoichiometry in AgCuS, which resulted in the vanishing of p–n–p-type conduction switching and improved its thermoelectric properties. We have performed the selective removal of cations and measured their temperature-dependent thermopower and Hall coefficient, which demonstrates only p-type conduction in the Ag1–xCuS and AgCu1–xS samples. The removal of Cu is much more efficient in arresting conduction switching, whereas in the case of Ag vacancy, p–n–p-type conduction switching vanishes at higher vacant concentrations. Positron annihilation spectroscopy measurements have been done to shed further light on the mechanisms behind this structural transition-dependent conduction switching. Cation (Ag+/Cu+) nonstoichiometry in AgCuS significantly increases the vacancy concentration, hence, the p-type carriers, which is confirmed by positron annihilation spectroscopy and Hall measurement. The Ag1–xCuS and AgCu1–xS samples exhibit ultralow thermal conductivity (∼0.3–0.5 W/m·K) in the 290–623 K temperature range because of the low-energy cationic sublattice vibration that arises as a result of the movement of loosely bound Ag/Cu within the stiff S sublattice.
Item Type: | Article |
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Source: | Copyright of this article belongs to American Chemical Society |
ID Code: | 128300 |
Deposited On: | 03 Nov 2022 05:56 |
Last Modified: | 03 Nov 2022 05:56 |
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