(x, y)

Na₂O (mol%)

Y₂O₃ (mol%)

B₂O₃ (mol%)

Al₂O₃ (mol%)

Y₂O₃/Al₂O₃

T_g^a (˚C)

(6, 0)

42.9

0.0

35.7

21.4

0.0

392

(4.8, 0.4)

36.4

3.0

37.9

22.7

0.13

449

(3.96, 0.66)

31.4

5.2

39.6

23.8

0.22

472

(3, 1)

25.0

8.3

41.7

25.0

0.33

512

(1.98, 1.32)

17.5

11.7

44.2

26.5

0.44

560

(1.2, 1.6)

11.1

14.8

46.3

27.8

0.53

630

(0, 2)

0.0

20.0

50.0

30.0

0.67

727