Abstract
The beta-Al2O3 solid electrolyte doped with Chromium was synthesized via a citrate-nitrate combustion method, which started with NaNO3, LiNO3, Cr(NO3)3·9H2O, and Al(NO3)3·9H2O as the raw materials in this paper. The thermal behavior analysis, structure, and ionic conductivity of the beta-Al2O3 solid electrolyte were studied by the thermogravimetry/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). Meanwhile, the relative density and bending strength of the samples were also measured. The results showed that with the appropriate Chromium doping, the calcining temperature of the precursor powders was only 1100 °C, the β″-Al2O3 phase content, bending strength, relative density, and ionic conductivity were all improved with a compact and uniform cross section micrograph. The optimized sample contained 94% of β″-Al2O3 phase and exhibited a relative density up to 98.13% of the theoretical density. In addition, it showed a good bending strength (215 MPa) and a satisficed ionic conductivity (0.110 S cm−1 at 350 °C).
Highlights
The beta-Al2 O3 solid electrolyte has a high ionic conductivity between 300 ◦ C and 350 ◦ C [1,2,3].It possesses the good prospects for the application of the electrolyte materials in the secondary batteries, such as sodium sulfur battery, sodium-nickel chloride battery, and other new types of Na+ conductor battery [4,5,6,7]
Wang et al [18] synthesized the beta-Al2 O3 ceramic material doped with CoO and the relative density reached a maximum of 97.98%, compared to only 95.55% of the non-doping sample
Khodael et al [22] studied the effect of Cr2 O3 additions on liquid-phase sintered SiC ceramics, the results showed that Cr2 O3 nanoparticles improved the densification of samples
Summary
The beta-Al2 O3 solid electrolyte has a high ionic conductivity between 300 ◦ C and 350 ◦ C [1,2,3].It possesses the good prospects for the application of the electrolyte materials in the secondary batteries, such as sodium sulfur battery, sodium-nickel chloride battery, and other new types of Na+ conductor battery [4,5,6,7]. The beta-Al2 O3 solid electrolyte has a high ionic conductivity between 300 ◦ C and 350 ◦ C [1,2,3]. It is crucial to prepare the electrolyte material with uniform composition, high density, and good ionic conductivity for the preparation of battery. Doping oxides in the ceramic materials had been indicated to improve the properties of the final samples. Some reports showed that an appropriate addition of Li2 O or MgO could improve the sodium ionic conductivity of the beta-Al2 O3 solid electrolyte [12,13,14,15,16]. S. Shan et al [17] reported that the beta-Al2 O3 solid electrolyte with TiO2 doping exhibited a bending strength up to 180 MPa compared to about 100 MPa without doping. The conductivity of the material increased the most from 0.022 S cm–1 for the Crystals 2020, 10, 987; doi:10.3390/cryst10110987 www.mdpi.com/journal/crystals
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