Physical, structural and optical properties of terbium doped zinc phosphate glasses embedded with copper oxide nanoparticles

Abstract

This thesis reports the modification of zinc phosphate glass properties as the concentration of terbium ion (Tb3+) and copper oxide nanoparticles (CuO NPs) are varied. Three series of glass with composition of (100-x) P2O5- xZnO with 30< x<80 mol% in Series 1, (60-x) P2O5- 40ZnO-xTb2O3, with 0.5< x<3.0 mol % in Series 2 and (57-x) P2O5- 40ZnO- 3Tb2O3-xCuO with 0.5<x<2.0 mol% in Series 3 had been prepared by melt quenching technique. It was observed that the glass samples in Series 1 and Series 2 were colourless and the glasses in Series 3 were blue in colour. The existences of the broad humps in X-ray diffraction (XRD) pattern clarify the amorphous nature of the glasses. The energy dispersive x-ray analysis (EDAX) detected the presence of the required elements in the glass composition. The presence of CuO NPs with the size of 0.11 nm in the glass matrix has been verified using high- resolution transmission electron microscope (HRTEM). The thermal properties and glass stability were determined using differential thermal analyser (DTA). The sample exhibited glass stability up to 287 oC. The glass density (?), molar volume (Vm) and ionic packing density (Vt) were found to be in the range of (2.86-3.60) g cm-3 , (25.90- 43.28) cm3 mol-1 and (0.582-0.741) respectively. The vibrational spectroscopy were analysed using Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy. Three major infrared absorption peak were found around 550 cm-1 , 794 cm-1 , 1165 cm-1 and 1264 cm-1 due to the vibration of (P-O) bond, stretching vibration of (P-O-P) bond, stretching vibrations (P=O) and asymmetric stretching vibration (P- O) bond. Surface plasmons resonance peak of CuO NPs was detected at 375 nm. The absorption spectra displayed five prominent bands owned to Tb3+ ion at 374 nm, 487 nm, 1878 nm, 1980 nm and 2231 nm. All these bands corresponded to 7F6?5D3, 7F6? 5D4, 7F6? 7F1,2 3 and 7F6? 7F3 transitions respectively. The optical energy band gap and Urbach energy were in the range of (2.95-4.84 eV) and (0.19-0.63 eV) respectively. Meanwhile, the refractive index, molar refractivity and electronic polarizability had been calculated in the range of (2.00-2.40), (16.42-28.80) and (0.65- 1.11) Å3 . The emissions of the glass with Tb3+ ion were determined using photoluminescence spectroscopy. The glass samples were excited at 378 nm excitation wavelength and the emission spectra were found to consist of several emission bands at 413 nm, 435 nm, 457 nm, 488 nm, 540 nm 585 nm and 620 nm due to electronic transitions from 5D3?7F5, 5D3?7F4, 5D3?7F3, 5D4?7F6, 5D4?7F5, 5D4?7F3 and 5D4?7F5 respectively. The presence of CuO NPs gave remarkable effects on the luminescent intensity. However, it was observed that the emission bands possess significant quenching effect at the higher concentration of CuO NPs.