Phase separation and crystallization in sodium lanthanum phosphate glasses induced by electrochemical substitution of sodium ions with protons

Keiga Kawaguchi, Takuya Yamaguchi, Takahisa Omata, Toshiharu Yamashita, Hiroshi Kawazoe, Junji Nishii

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

Electrochemical substitution of sodium ions with protons (alkali-proton substitution; APS), and the injection of proton carriers was applied to sodium lanthanum phosphate glasses. A clear and homogeneous material was obtained for a glass of composition 25NaO1/2-8LaO3/2-66PO5/2-1GeO2 following APS, with a resulting proton conductivity of 4 × 10-6 S cm-1 at 250 °C. The glass underwent phase separation and crystallization at temperatures > 255 °C, forming a highly hygroscopic and proton conducting H3PO4 phase in addition to LaP5O14 and other unidentified phases. A glass of composition 25NaO1/2-8LaO3/2-67PO5/2 underwent phase separation and crystallization during APS, forming both H3PO4 and LaP5O14 phases. Sodium lanthanum phosphate glasses are prone to phase separation and crystallization during APS unlike the previously reported NaO1/2-WO3-NbO5/2-LaO3/2-PO5/2 glasses. The phase separation was explained by a reduction in viscosity following APS and the introduction of protons, which exhibit high field strength. Thus, phase separation and crystallization of glasses during APS was difficult to avoid. An approach to suppress phase separation is discussed.

Original languageEnglish
Pages (from-to)22855-22861
Number of pages7
JournalPhysical Chemistry Chemical Physics
Volume17
Issue number35
DOIs
Publication statusPublished - 2015 Aug 4
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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