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|a Two series of glass based on composition 50P2O5 - 48MgO - (2-x)Er2O3 - xNd2O3, where 0.5 ≤ x ≤ 1.5 mole % and (50-y)P2O5 - 48MgO - 2Er2O3 - yNd2O3, where 0.5 ≤ y ≤ 2.0 mole % have successfully been prepared by melt-quenching technique. The X-ray diffraction (XRD) analysis shows that all samples are in amorphous state and their density is found to be in the range of (2.568 - 2.686) gcm-3. The vibrational study is conducted using the Infrared (IR) spectroscopy in the range of 400 - 4000 cm-1. It is observed that the vibrational frequency occur around 3454 - 3564 cm-1, 1298 - 1318 cm-1, 1082 - 1085 cm-1, 923 - 935 cm-1, 727 - 776 cm-1, and 468 - 498 cm-1 which is predominately due to the OH bending vibration, P=O asymmetric stretching vibration modes, symmetric stretch of PO2, asymmetric stretch of P-O-P bridges (vas (P-O-P)), symmetric stretching vibration of P-O-P bond (vs (PO- P)) and bending vibration of P=O unit, modes of 3- 4 PO chain groups respectively. The UV-Vis-NIR spectroscopy analysis shows that the absorption characteristic consist of several significant absorption peaks around 872 nm, 801 nm, 743 nm, 580 nm, 1536 nm, 977 nm, 652 nm, 522 nm, 487 nm, 451 nm, and 406 nm which correspond to the transitions of both Nd3+ and Er3+ ions. The experimental and calculated oscillator strength is found to vary from 2.443 x 10-7 to 1.002 x 10-7 and from 1.801 x 10-7 to 0.745 x 10-7 respectively. The Judd-Ofelt intensity parameters Ω2 varies from 1.968 x 10-22 cm2 to 13.572 x 10-22 cm2 while the value of Ω4 and Ω6 varies from 0.264 x 10-22 cm2 to 11.007 x 10-22 cm2 and from 0.775 x 10-22 cm2 to 4.895 x 10-22 cm2 respectively. It is also found that the energy gap, Eg and the Urbach energy, ∆E is in the range of 3.86-3.98 eV and 1.67 - 1.86 eV respectively, depending on the Nd2O3 concentration.
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