α-alumina and spinel react into single-phase high-alumina spinel in <3 seconds during flash sintering

David Kok, Devinder Yadav, Emanuele Sortino, Scott J. McCormack, Kuo Pin Tseng, Waltraud M. Kriven, Rishi Raj, Martha L. Mecartney

Research output: Contribution to journalArticlepeer-review

Abstract

In situ X-ray diffraction measurements at the Advanced Photon Source show that α-Al 2 O 3 and MgAl 2 O 4 react nearly instantaneously and completely, and nearly completely to form single-phase high-alumina spinel during voltage-to-current type of flash sintering experiments. The initial sample was constituted from powders of α-Al 2 O 3 , MgAl 2 O 4 spinel, and cubic 8 mol% Y 2 O 3 -stabilized ZrO 2 (8YSZ) mixed in equal volume fractions, the spinel to alumina molar ratio being 1:1. 5. Specimen temperature was measured by thermal expansion of the platinum standard. These measurements correlated well with a black-body radiation model, using appropriate values for the emissivity of the constituents. Temperatures of 1600-1736°C were reached during the flash, which promoted the formation of alumina-rich spinel. In a second set of experiments, the flash was induced in a current-rate method where the current flowing through the specimen is controlled and increased at a constant rate. In these experiments, we observed the formation of two different compositions of spinel, MgO•3Al 2 O 3 and MgO•1.5Al 2 O 3 , which evolved into a single composition of MgO•2.5Al 2 O 3 as the current continued to increase. In summary, flash sintering is an expedient way to create single-phase, alumina-rich spinel.

Original languageEnglish (US)
JournalJournal of the American Ceramic Society
Volume102
Issue number2
DOIs
StatePublished - 2019

Keywords

  • Alumina
  • Composites
  • Field assisted sintering technology
  • Spinels
  • Zirconia: yttria stabilized

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry

Fingerprint Dive into the research topics of 'α-alumina and spinel react into single-phase high-alumina spinel in <3 seconds during flash sintering'. Together they form a unique fingerprint.

Cite this