Effect of Stepwise Replacement of LiF by Bi₂O₃ and of Annealing on Optical Properties of LiF⋅B₂O₃ Glasses

Table 1

Cutoff wavelength (λ _cutoff), optical band gap energy 𝐸_𝑔 and Urbach energy (𝐸_𝑈) for the samples with 𝑥=0,5,10,15, and 20 in the compositions xBi₂O₃·(40 − x)LiF·60 B₂O₃.

	𝑥 (mol%)	𝜆cutoff (nm)	𝐸𝑔 (eV)	𝐵 (cm eV)^−1	𝐸𝑈 (eV)
As Prepared	0	334	3.32	1.614	0.510
	5	384	3.00	1.868	0.231
	10	408	2.78	1.932	0.213
	15	433	2.68	2.003	0.213
	20	442	2.62	2.095	0.194
Annealed at 300°C	0	377	2.46	1.073	1.376
	5	394	2.85	1.614	0.499
	10	410	2.77	1.868	0.404
	15	413	2.74	1.932	0.364
	20	416	2.73	2.003	0.296
Annealed at 350°C	0	361	2.43	0.745	1.842
	5	400	2.93	1.432	0.649
	10	419	2.88	1.868	0.488
	15	432	2.85	2.003	0.456
	20	426	2.84	2.081	0.404
Annealed at 400°C	0	361	2.56	1.036	1.428
	5	377	3.28	1.809	0.384
	10	413	2.96	2.003	0.404
	15	416	2.89	2.081	0.344
	20	423	2.87	2.268	0.364