A dramatic reduction in the sintering temperature of the refractory sodium β′′-alumina solid electrolyte via cold sintering. Issue 38 (22nd September 2021)

• Record Type: Journal Article
• Authors: Grady, Zane; Ndayishimiye, Arnaud; Randall, Clive
• Is Part Of: Journal of materials chemistry. Volume 9:Issue 38(2021)
• Page Start: 22002
• Page End: 22014
• Publication Date: 2021-09-22
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d1ta05933e
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : The refractory solid electrolyte, sodium beta alumina, is cold sintered at 375 °C which is over 1000 °C lower than conventional sintering. A relative density above 90% and an ionic conductivity of 10 −3 S cm −1 (300 °C) is obtained. Abstract : The cold sintering process is successfully applied to one of the most refractory solid-state sodium-ion electrolytes, namely sodium beta alumina (SBA). By using a hydroxide-based transient solvent, SBA is densified below 400 °C, whereas conventional solid-state sintering is known to require sintering temperatures around 1600 °C. This dramatic reduction in sintering temperature ( ca. T sinter ∼ 20% of T m ) is achieved by cold sintering with the addition of 10 wt% solid NaOH transient phase, 360 MPa of uniaxial pressure, and heating to 350–375 °C, for a dwell time of three hours. The resulting pellets exceed 90% of the theoretical density for SBA and exhibit ionic conductivities of ∼10 −2 S cm −1 at 300 °C, as measured by electrochemical impedance spectroscopy. The structural changes occurring during cold sintering are reversed with an intermediate temperature annealing step ( ca. 1000 °C) which improves the ionic conductivity. This study therefore highlights the opportunities and remaining challenges in applying cold sintering to refractory, air-sensitive, electroceramics.