Abstract:
The Yb
3+ doped borophosphate glasses were prepared by the melt-quenching method. The effect of B
2O
3 on optical properties was investigated, and stark splitting of Yb
3+ was obtained by fitting the absorption and emission spectra. Based on fitting results, the crystal field strength parameter
NJ and asymmetry of the surrounding ligand structure were calculated which was used to explain the change of luminescence properties and Yb
3+ local environment with the help of structure information. The results show that B
2O
3 is good for enlarging the Stark splitting of Yb
3+ and changing the local environment. Compared with the previous single PO
4 ligand, the difference in bond length of BO
4-Yb and PO
4-Yb will increase the asymmetry of Yb
3+. In addition, the electronegativity of P is stronger than that of B, and the reciprocity between P and O in PO
4 is stronger than that of BO
4, so the interaction between BO
4 and Yb
3+ is stronger than that between PO
4 and Yb
3+. Therefore, when
x_\rmB_2O_3>10% was applied, the degree of asymmetry and
NJ increased, which enhanced the fluorescence intensity around Yb
3+. Besides, with the increase of B
2O
3 mole fraction, the introduced B
2O
3 all exist in the form of BO
4, and BPO
4 structure units are formed by alternating connection with PO
4. Therefore, B
2O
3 could connect phosphate long chains and glass network transfers from chain structure to three-dimensional space which contributes to enhance the chemical stability and improve the environment of Yb
3+. Borophosphate glass is expected to be a high power ytterbium-doped matrix material.