Premium
Prominent Nanocrystallization of 25K 2 O·25Nb 2 O 5 ·50GeO 2 Glass
Author(s) -
Narita Kazuhiro,
Takahashi Yoshihiro,
Benino Yasuhiko,
Fujiwara Takumi,
Komatsu Takayuki,
Hanada Takeshi,
Hirotsu Yoshihiko
Publication year - 2004
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2004.00113.x
Subject(s) - materials science , crystallization , vickers hardness test , orthorhombic crystal system , volume fraction , nanoindentation , glass transition , phase (matter) , analytical chemistry (journal) , nanocrystal , mineralogy , crystallography , composite material , chemical engineering , microstructure , crystal structure , nanotechnology , chemistry , organic chemistry , chromatography , engineering , polymer
Some K 2 O‐Nb 2 O 5 ‐GeO 2 glasses are prepared, and their crystallization behaviors are examined. 25K 2 O·25Nb 2 O 5 ·50GeO 2 glass with the glass transition temperature T g = 622°3C and crystallization onset temperature T x = 668°3C shows a prominent nanocrystallization. The crystalline phase is K 3,8 Nb 5 Ge 3 O 20,4 with an orthorhombic structure. The sizes of crystals in the crystallized glasses heat‐treated at 630° and 720°3C for 1 h are °10 and 20–30 nm, respectively, and the crystallized glasses obtained by heat treatments at 620°‐850°3C 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°3C for 1 h is estimated to be ∼35%. The usual Vickers hardness and Martens hardness (estimated by nanoindentation) of 25K 2 O·25Nb 2 O 5 ·50GeO 2 glass change steeply by heat treatment at T g , 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.