Structural analysis of alkali cations in mixed alkali silicate glasses by ²³Na and ¹³³Cs MAS NMR

Peer review under responsibility of The Ceramic Society of Japan and the Korean Ceramic Society.

Figures & data

Table 1 Compositions of the xNa₂O-yCs₂O-2SiO₂ glasses (y = 1.0, 0.8, 0.66, 0.5, 0.33, 0.2; x + y = 1) analyzed by using XRF. The amount of alkali oxides was calculated as SiO₂ = 2.

x	Na2O	Cs2O	SiO2
0.00	–	1.00	2
0.20	0.18	0.82	2
0.33	0.31	0.66	2
0.50	0.49	0.52	2
0.67	0.61	0.38	2
0.80	0.76	0.14	2
0.00	0.95	–	2

Fig. 1 XRD pattern of Cs₂Si₂O₅ crystal. The XRD pattern of the standard Cs₂Si₂O₅ crystal obtained from the simulation using POWDER CELL is also provided for reference. The hollow pattern is due to the borosilicate glass tube that was used to avoid water absorption.

Fig. 2 XRD pattern of Cs₆Si₁₀O₂₃ crystal. The XRD pattern of standard Cs₆Si₁₀O₂₃ crystal obtained from the simulation using POWDER CELL is also provided for reference.

Fig. 3 ¹³³Cs MAS NMR spectra of cesium silicate crystals.

Fig. 4 ²³Na MAS NMR spectra of xNa₂O-yCs₂O-2SiO₂ glasses (x = 0.2, 0.33, 0.5 0.66, 0.8, 1.0; x + y = 1).

Fig. 6 Relationship between Cs–O distances and coordination numbers in Cs₂Si₂O₅. There exist four kinds of cesium that are crystallographically independent.

Fig. 7 Relationship between Cs–O distance and coordination number in Cs₆Si₁₀O₂₃.

Fig. 5 ¹³³Cs MAS NMR spectra of xNa₂O-yCs₂O-2SiO₂ glasses (y = 1.0, 0.8, 0.66, 0.5, 0.33, 0.2; x + y = 1).

Table 2 Estimated coordination numbers of Na and Cs in xNa₂O-yCs₂O-2SiO₂ glasses (x + y = 1) by using Eq. (1)(1) $N_{\text{c}}=-0.814{\sigma }_{\text{Cs}}+24.4$(1) . N_Na and N_Cs are the coordination numbers of Na and Cs, respectively.

	y
	0	0.2	0.33	0.5	0.66	0.8	1
NNa	9.0	8.1	7.6	7.6	7.5	7.3
NCs		16.3	15.8	15.4	14.6	13.2	11.1

Fig. 8 Average coordination numbers of Na⁺ and Cs⁺ in xNa₂O-yCs₂O-2SiO₂ glasses (y = 1.0, 0.8, 0.66, 0.5, 0.33, 0.2; x + y = 1).