Adamu, M and Kale, GM (2016) Novel Sol–Gel Synthesis of MgZr₄P₆O₂₄ Composite Solid Electrolyte and Newer Insight into the Mg²⁺-Ion Conducting Properties Using Impedance Spectroscopy. Journal of Physical Chemistry C, 120 (32). pp. 17909-17915. ISSN 1932-7447
Abstract
Magnesium zirconium phosphate, MgZr₄P₆O₂₄ (MZP), is a magnesium ion conducting ceramic material with potential for application as solid electrolyte in high temperature electrochemical sensor in non-ferrous scrap metal refining and virgin metal alloying operations. In this work, MZP was synthesized using a simple but novel and economical sol–gel route at a significantly reduced temperature. An insight into the calcination process and possible phase transformation at higher temperature was obtained using simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA/DSC). Phase identification of the synthesized material was studied after calcining the powder at 900 °C for 3 h using X-ray diffraction (XRD); a single monoclinic phase was observed at that temperature. However, a trace amount of possible minor second phase, zirconium oxide phosphate [Zr2(PO4)2O], was formed after heating at temperatures T ≥ 1000 °C. Impedance spectroscopy measurements on platinized sintered-MZP pellets were carried out in the frequency range 100 mHz to 32 MHz and in a temperature range of 30–800 °C to determine the electrical properties of MZP. Ionic conductivity of MZP was found to be equal to 7.23 × 10–3 Ω–1 cm–1 at relatively lower temperature, 725 °C. Furthermore, the Nyquist and modulus plots measured at 764 and 390 °C show single semicircles suggesting contribution from only grain interiors (GIs). The ion-hopping rate was calculated by fitting the conductance spectra to the power law variation, σac (ω) = σdc + Aωn. The ac and dc conductivity of MZP shows Arrhenius-type of behavior with activation energies in the range 0.84 ≤ Ea(eV) ≤ 0.87. SEM of the fractured MZP pellet sintered at 1300 °C for 24 h revealed a highly dense microstructure with clearly visible grain boundaries and low porosity which is in good agreement with the relative density of ∼99% determined using the Archimedes’ principle and the theoretical density calculated from the crystal structure. EDS confirms the presence of Mg, Zr, P, O in appropriate atomic ratio to yield MgZr4P6O24. Finally, TEM on MZP particles with crystallite size of ∼50 nm also confirmed MZP as stable at 900 °C with no observable second phase, Zr2(PO4)2O.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2016, American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.jpcc.6b05036. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemical & Process Engineering (Leeds) > Institute for Materials Research (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 22 Jul 2016 10:45 |
Last Modified: | 21 Jul 2017 20:47 |
Published Version: | http://dx.doi.org/10.1021/acs.jpcc.6b05036 |
Status: | Published |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/acs.jpcc.6b05036 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:102793 |