Effects of composition and growth parameters on phase formation in multicomponent aluminum garnet crystals

Matheus Pianassola, Marlena Alexander, Bryan Chakoumakos, Merry Koschan, Charles Melcher, Mariya Zhuravleva

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

The effects of composition on the phase formation of multicomponent garnet crystals grown via directional solidification by the micro-pulling-down method are studied. A relatively wide range of rare-earth (RE) average ionic radii (AIR) is explored by formulating ten compositions from the system (Lu,Y,Ho,Dy,Tb,Gd)3Al5O12. Crystals were grown at either 0.05 or 0.20 mm min-1. The hypothesis is that multicomponent compounds with large AIR will form secondary phases as the single-RE aluminum garnets formed by larger Tb3+ or Gd3+; this will result in crystals of poor optical quality. Crystals with large AIR have a central opaque region in optical microscopy images, which is responsible for their reduced transparency compared to crystals with small AIR. Slow pulling rates suppress the formation of the opaque region in crystals with intermediate AIR. Powder and single-crystal X-ray diffraction and electron probe microanalysis results indicate that the opaque region is a perovskite phase. Scanning electron microscopy and energy dispersive spectroscopy measurements reveal eutectic inclusions at the outer surface of the crystals. The concentration of the eutectic inclusions increases with increasing AIR.

Original languageEnglish
Pages (from-to)476-484
Number of pages9
JournalActa Crystallographica Section B: Structural Science, Crystal Engineering and Materials
Volume78
Issue numberPt 3 Pt 2
DOIs
StatePublished - Jun 1 2022

Keywords

  • crystal growth
  • garnet crystals
  • micro-pulling-down
  • multicomponent oxide

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