Effects of borate substitution on the structural, optical, and physical properties of CuO-Doped sodium zinc phosphate glasses

A series of phosphate glasses based on a P2O5 network and containing sodium oxide (Na2O), copper oxide (CuO), zinc oxide (ZnO), and various borate additives was fabricated using the melt-quenching technique. The phosphate network showed the vibration of PO4 units in Q2 mode as major structural units and in Q1 and Q3 modes as minor units. Upon introduction of B2O3 into the P2O5 network, the glass density (D) decreased slightly from 2.754 g/cm3 to 2.660 g/cm3. The presence of a small amount of CuO (1 mol%) affected the optical transmittance, exhibiting a blocking transmission zone from 758 nm to 1250 nm, as in the base P2O5 glass. In addition, B2O3 increased the optical transmittance and affected the blocking transmission zone. The energy gap (Eg) increased from 3.447 eV in glass without B2O3 to 3.662 eV in glass with 12.5 mol% B2O3, while the static refractive index (n0) decreased from 2.276 to 2.245. The nonlinear refractive index (n2) was investigated in terms of the refractive index and dispersion parameters, and its value decreased from 1.943 × 10–11 esu to 1.611 × 10–11 esu as the B2O3 content increased. Such glasses are suggested for use in optical semiconductor applications, such as optical bandpass filters.