Chapter 10
New Na + Superionic Conductor Narpsio
Glass-Ceramics
Toshinori Okura and Kimihiro Yamashita
Abstract This review article describes a series of studies on glass-ceramic
Na + superionic conductors with the Na 5 YSi 4 O 12 (N5)-type structure and with
a Na 3+3x−y R 1−x P y Si 3−y O 9 composition, where R is a rare earth element. In
the crystallization of N5-type glass-ceramics, its relatives (Na 3 YSi 3 O 9 (N3)and Na 9 YSi 6 O 18 (N9)-type glass-ceramics) structurally belonging to the family
of Na 24−3x Y x Si 12 O 36 were found to crystallize as the precursor phase at low
temperatures. In order to produce N5 single-phase glass-ceramics, the concentration
of both phosphorus and rare earth was found important. The meaning of the
composition was evaluated by kinetic study on the phase transformation of
metastable N3 or N9 phases to stable N5 phase with Na + superionic conductivity.
The possible combinations of x and y became more limited for the crystallization
of the superionic conducting phase as the ionic radius of R increased, while the
Na + conduction properties were more enhanced in the glass-ceramics of larger R.
These results are discussed in view of the structure and the conduction mechanism.
Also discussed were the microstructural effects on the conduction properties,
which were dependent upon the heating conditions of crystallization. These effects
were understood in relation to the grain boundary conduction properties as well
as the transmission electron microstructural morphology of grain boundaries.
Recent research into the effects of microstructure on conduction properties and
microstructural control of Na + superionic conducting glass-ceramics is also
introduced. The optimum conditions for crystallization are discussed with reference
to the conduction properties and the preparation of crack-free N5-type glassceramics. The effects of substituting Si with other elements exhibiting tetrahedral
oxygen coordination and substituting Y with various rare earth elements are also
T. Okura ()
Department of Applied Chemistry, School of Advanced Engineering, Kogakuin University,
Tokyo, Japan
e-mail: okura@cc.kogakuin.ac.jp
K. Yamashita
Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
e-mail: yama-bcr@tmd.ac.jp
© Springer Nature Singapore Pte Ltd. 2020
T. Onishi (ed.), Theoretical Chemistry for Advanced Nanomaterials,
https://doi.org/10.1007/978-981-15-0006-0_10
383
New Na + Superionic Conductor Narpsio
Glass-Ceramics
Toshinori Okura and Kimihiro Yamashita
Abstract This review article describes a series of studies on glass-ceramic
Na + superionic conductors with the Na 5 YSi 4 O 12 (N5)-type structure and with
a Na 3+3x−y R 1−x P y Si 3−y O 9 composition, where R is a rare earth element. In
the crystallization of N5-type glass-ceramics, its relatives (Na 3 YSi 3 O 9 (N3)and Na 9 YSi 6 O 18 (N9)-type glass-ceramics) structurally belonging to the family
of Na 24−3x Y x Si 12 O 36 were found to crystallize as the precursor phase at low
temperatures. In order to produce N5 single-phase glass-ceramics, the concentration
of both phosphorus and rare earth was found important. The meaning of the
composition was evaluated by kinetic study on the phase transformation of
metastable N3 or N9 phases to stable N5 phase with Na + superionic conductivity.
The possible combinations of x and y became more limited for the crystallization
of the superionic conducting phase as the ionic radius of R increased, while the
Na + conduction properties were more enhanced in the glass-ceramics of larger R.
These results are discussed in view of the structure and the conduction mechanism.
Also discussed were the microstructural effects on the conduction properties,
which were dependent upon the heating conditions of crystallization. These effects
were understood in relation to the grain boundary conduction properties as well
as the transmission electron microstructural morphology of grain boundaries.
Recent research into the effects of microstructure on conduction properties and
microstructural control of Na + superionic conducting glass-ceramics is also
introduced. The optimum conditions for crystallization are discussed with reference
to the conduction properties and the preparation of crack-free N5-type glassceramics. The effects of substituting Si with other elements exhibiting tetrahedral
oxygen coordination and substituting Y with various rare earth elements are also
T. Okura ()
Department of Applied Chemistry, School of Advanced Engineering, Kogakuin University,
Tokyo, Japan
e-mail: okura@cc.kogakuin.ac.jp
K. Yamashita
Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
e-mail: yama-bcr@tmd.ac.jp
© Springer Nature Singapore Pte Ltd. 2020
T. Onishi (ed.), Theoretical Chemistry for Advanced Nanomaterials,
https://doi.org/10.1007/978-981-15-0006-0_10
383