Prominent nanocrystallization of 25K2O·25Nb2O5·50GeO2 glass

Kazuhiro Narita, Yoshihiro Takahashi, Yasuhiko Benino, Takumi Fujiwara, Takayuki Komatsu, Takeshi Hanada, Yoshihiko Hirotsu

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)


Some K2O-Nb2O5-GeO2 glasses are prepared, and their crystallization behaviors are examined. 25K2O·25Nb2O5·50GeO2 glass with the glass transition temperature Tg = 622°C and crystallization onset temperature Tx = 668°C shows a prominent nanocrystallization. The crystalline phase is K3.8Nb5Ge3O20.4 with an orthorhombic structure. The sizes of crystals in the crystallized glasses heat-treated at 630° and 720°C for 1 h are ∼10 and 20-30 nm, respectively, and the crystallized glasses obtained by heat treatments at 620°-850°C for 1 h maintain good transparency. The density of crystallized glasses increases gradually with increasing heat-treatment temperature, and the volume fraction of crystals in the sample heat-treated at 630°C for 1 h is estimated to be ∼35%. The usual Vickers hardness and Martens hardness (estimated by nanoindentation) of 25K2O·25Nb2O5·50GeO2 glass change steeply by heat treatment at Tg, i.e., at around 35% volume fraction of nanocrystals. The present study demonstrates that the composite of nanocrystals and the glassy phase has a strong resistance against deformation during Vickers indenter loading in crystallized glasses.

Original languageEnglish
Pages (from-to)113-118
Number of pages6
JournalJournal of the American Ceramic Society
Issue number1
Publication statusPublished - Jan 2004
Externally publishedYes

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry


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