MAS-NMR measurements, 0.2 mol% of $ Fe_{2}O_{3} $ was added to the glass batches in order to shorten the relaxation time. NMR measurements were carried out at 7.05 T on a Varian Unity Inova 300 spectrometer, and the respective conditions of $ {}^{29}Si $ , $ {}^{11}B $ and $ {}^{31}P $ measurements were as follows: frequency = 59.6 MHz, 96.2 MHz and 121.4 MHz, sample spinning speed = 5.0 kHz (all), pulse duration = 2.5 $ \mu $ s, 0.6 $ \mu $ s and 3.3 $ \mu $ s, repetition time = 1.0 s (all), chemical shift second standard = polydimethyl siloxane (PDMS), $ BPO_{4} $ and $ NH_{4}H_{2}PO_{4} $ .

### 3. Result and discussion

Figure 1 shows the SEM photographs of the surfaces of the heat-treated samples. Regardless of $ P_{2}O_{5} $ or $ TiO_{2} $ typical morphologies due to spinodal decomposition are commonly confirmed. In the DTA curve of the glasses No. 4, an exothermic peak due to crystallization was observed above $ 600\;^{\circ}C $ (See $ T_{x} $ in Table 1). As shown in Figure 2, $ TiO_{2} $ crystal (anatase type) is precipitated in this glass after heat treatment at $ 660\;^{\circ}C $ .

(a)

(b)

Figure 1. SEM photographs of the surfaces of the glasses heated at $ 600^{\circ} $ C for 16 h. (a) glass No. 1 (b) glass No. 3

Figure 2. XRD pattern of glass No. 4 heated at $ 600^{\circ} $ C for 16 h.

Table 2 shows the chemical compositions of the glass phases after phase separation obtained from ICP and XRF analyses. As shown in Table 2, phosphorus in the $ TiO_{2} $ -free glass No. 2 is preferentially distributed into $ B_{2}O_{3} $ -rich glass phase after the phase separation. This is related to the charge of $ PO_{4} $ units [3]. On the other hand, in the $ TiO_{2} $ -containing glasses No. 3 and No. 4 phosphorus is distributed also into $ SiO_{2} $ -rich glass phase. In addition, the amount of phosphorus distributed into $ SiO_{2} $ -rich glass phase increases with increasing $ TiO_{2} $ ratio. Moreover, titanium is preferentially distributed into $ SiO_{2} $ -rich glass phase. However, in the sample No. 4 in which $ TiO_{2} $ is precipitated, the amount of phosphorus distributed into $ SiO_{2} $ -rich glass phase decreases. It is suggested that the distribution of phosphorus is clearly affected by titanium atom.

Table 2. Analytical composition of the glass phases after phase separation

$$ \mathrm{S i O_{2}-r i c h} $$

No.	Na_{2}O	B_{2}O_{3}	SiO_{2}	P_{2}O_{5}	TiO_{2}
2	0.0	4.2	95.7	0.1	-
3	0.1	-	89.0	2.8	8.1
4	0.1	-	83.2	3.3	13.4
4'	0.2	-	84.3	0.5	15.0

(b) B2O3-rich phase (mol%)

No.	Na_{2}O	B_{2}O_{3}	SiO_{2}	P_{2}O_{5}	TiO_{2}
2	18.1	73.1	2.8	6.0	-
3	16.4	76.4	3.0	3.5	0.7
4	16.8	76.4	2.8	3.1	0.9
4'	19.0	72.5	3.6	4.8	0.1

4': glass No. 4 heated at $ 660\;^{\circ}C $ . Glasses No. 2 - 4 were heated at $ 600\;^{\circ}C $

Acknowledgement:

The authors gratefully acknowledge the financial support of Grant-in-Aid for Scientific Research in Establishing a Sound Material-Cycle Society (K2132, K22052), Ministry of Environment, Japan.

## Reference:

[1] T. Nanba, S. Mikami, T, Imaoka, S. Sakida, Y. Miura, J. Ceram Soc. Jpn., 116(2) 220-223 (2008)

[2] T. Nanba, Y. Kuroda, S. Sakida, Y. Miura, J. Ceram Soc. Jpn., 117(11) 1195-1198 (2009)

[3] Y. Ohtsuki, S. Sakida, Y. Benino, T. Nanba, Proceedings in the 3rd International Congress on Ceramics (ICC3), S8-P033, (2010) Osaka.