Synthesis of large ETS-4 crystals in the Na and Na/K systems: The effects of alkali metal ion and synthesis mixture alkalinity

Bilge Yilmaz, Juliusz Warzywoda, Albert Sacco

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

The effects of Si/Ti ratio, initial pH, type of pH modifier and alkali metal cation system on ETS-4 crystal size and morphology were investigated. In the Na system at lower initial pH values (11.50-12.80), polycrystalline ETS-4 was obtained from all synthesis mixtures investigated (Si/Ti = 3.0-3.6), using either base (sodium hydroxide) or acid (sulfuric acid) as a pH modifier. When the initial pH was adjusted to range from 12.90 to 13.50 using acid, base or a combination of both, monolithic ETS-4 crystals with rectangular prism morphology were obtained. The average length of these crystals increased from ~15 μm at pH = 12.90 to ~40 μm at pH= 13.50. These results indicate that in the Na system, morphology and size of ETS-4 are not directly related to the synthesis mixture Si/Ti ratio or the type of pH modifier used. The strong dependence of crystal characteristics on the initial pH suggests that alkalinity is a major factor affecting ETS-4 crystallization. When half of the Na ions were replaced by K ions in synthesis mixtures with initial pH = 12.90, the resulting Na/K system yielded large single ETS-4 crystals with average dimensions ~10 × 200 × 20 μm. These are the largest ETS-4 crystals reported to date. These results suggest a structure-breaking role for K ions in ETS-4 crystallization.

Original languageEnglish
Pages (from-to)325-331
Number of pages7
JournalJournal of Crystal Growth
Volume271
Issue number1-2
DOIs
StatePublished - Oct 15 2004

Keywords

  • A1. Crystal morphology
  • A2. Large crystal growth
  • A2. Synthesis
  • A3. Quantum wires
  • B1. ETS-4
  • B1. Titanosilicates

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