Results and discussion
3.1. X-ray diffraction, SEM and EDS analysis
The XRD spectra of Nd3+ and Pr3+ doped ZANP glass matrices were recorded and they exhibit a broad diffuse scattering at small angles instead of crystalline peaks, confirming a long range structural disorder characteristic of amorphous network and thus glassy state was confirmed. SEM images of 1.0 mol% of Nd3+ and Pr3+ doped ZANP glass matrices do not show any grains indicating amorphous nature of the glass samples.
3.2. Raman spectra of glasses
The Raman scattering spectra at room temperature for the host (ZANP) glass is shown in Fig. 1. It is a known fact that phosphate network is built up from corner-sharing PO4 tetrahedral units. According to the number of bridging oxygens the tetrahedral units are usually represented by their connectivity Qn (where n = 1, 2 and 3) [20]. Here n is the number of bridging oxygens per PO4 tetrahedron. For example Q2 units often called View the MathML source units have two non-bridging oxygens and two bridging oxygens. In the case of Raman spectrum, the peak nearly at 357 cm−1 is attributed to bending vibration of PO4 units with cation as modifier. The peak at 545 cm−1 is attributed to bending and torsional vibrations of (P2O7)4− groups. The peak centered at 698 cm−1 is attributed to symmetrical stretching mode of Psingle bondOsingle bondP bridging bond in Q1 units [21] and [22]. The peak nearly at 1042 cm−1 is owing to the asymmetric vibration of (PO3)as groups, Q1 units [23] and [24]. The spectrum exhibits maximum intensity at 1162 cm−1 which is due to symmetrical stretching vibration of (PO2) units [23] and [25]. This band possesses maximum phonon energy for the host glass, which plays an important role on the emission properties of the luminescent ions. The weak band that appears at 1262 cm−1 is assigned to Pdouble bond; length as m-dashO asymmetrical stretching mode [26]