珪酸塩系のガラス化範囲について : ガラス化範囲の研究(第2報)

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Following a previous report "Studies of the Glass-formation Range of Borate Systems" (This Journal, 69, 282 (1961)), we studied the glass-formation range of silicate systems. Although silicate glasses have long been used, sufficient systematic studies of the glassformation ranges of silicate systems have not yet been made. In this experiment, 1/80 mole (about Ig.) of materials were melted in crucibles made of pure platinum, or platinum containing 2096 rhodium at temperatures from 1400° to 1750℃. The oxides used besides SiO2 were 16 kinds of the oxides of a-group elements namely Li, Na, K, Be, Mg, Ca, Sr, Ba, Al, La, Ti, Zr, Th, Nb, Ta and W. The glass-formation ranges of binary silicate systems are shown in Table 1. These ranges differ in some points from those of borate systems. For instance, the La-silicate system has no vitrified range, while the Mg-silicate system, has a wider glass-formation range than the borate. Whether a component ion enters into the glass structure as a modifier or as a network-former depends on the acidity of the glass-former and on the electronegativity of the component ion. In silicate systems, however, the actual range of glass-formation equals the difference between the glass-formation range and the immiscible range. If the latter is equal to the former or somewhat wider, the vitrified range will disappear. The glass-formation ranges of ternary systems are shown in Fig. 1〜34. The whole number of the studied systems reached about one hundred. The Experimental results show that the actual glass-formation ranges agree with the range (hatched areas in the figures) to be expected from the "Conditions of Glass-formation" (This Journal, 67, 364 (1959)). Among these systems, the systems containing TiO_2 (cf. Figs. 12 and 13) are remarkably different from the corresponding borate systems. In the borate systems, a glass-fromation range spreads on the right side of the SiO_2-D line (cf. Fig, 10), and therefore it has been estimated that the co-ordination number of Ti4+ is 6. (In order for the Ti4+ ion to take 6-co-ordination as a network-former, the modifier of divalency must also be present, therefor, in the area on the left of the SiO_2-D line glass-formation is impossible.) However, in the silicate system the limited line of SiO_2-D is lacking. Consequently, it is concluded that the Ti^<4+> ion as well as the Si^<4+> ion takes the 4-co-ordination. The glass-formation range of the TiO_2-containing systems are shown in the hatched areas of Figs. 12 and 13, which are limited by the AD line. The WO_3-containing silicate systems have a remarkably narrow glass-formation range compared with borate systems. The vitrified range of the B_2O_3-WO_3-alkali oxide system has two feet, but the silicate system, we suppose, lacks the left foot. Moreover, it is considered that the left foot consists of WO_3 and alkali borate in borate systems, but that this part becomes immiscible in silicate systems. According to the devitrification of the binary system, La_2O_3 systems are classified as C-type ternary systems, and their glass-formation ranges are narrower than those of borate systems. The vitrified range of the SiO_2-Al_2O_3-La_2O_3 system (cf. Fig. 29) agrees with that of the corresponding borate system, but the limiting line, kl, of the immiscible range is lower than .that of the borate and, accordingly the glass-formation range of the former is narrower than that of the latter. Other La-silicate systems are similar. Among the C-type ternary systems containing ThO_2 or Al_2O_3, which have vitrified ranges in case of the corresponding borate systems, we found the glassy state only in the SiO_2-ThO_2-Al_2O_3 system (Fig. 33) and the SiO_2-BeO-Al_2O_3 system (Fig. 34). The results of our experiment did not confirm the vitrified range in the SiO_2-ZrO_2-Al_2O_3 system which had been reported by Heynes and Rawson.
社団法人日本セラミックス協会の論文
1963-12-01

珪酸塩系のガラス化範囲について : ガラス化範囲の研究(第2報)

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