ESR and optical investigation of tetragonal PbTiO3 nanoparticles embedded in lithium tetraborate glass matrix

Glass-nanocomposites (GNCs) samples of composition [(100−x) Li 2 B 4 O 7 –xPbTiO 3 ] with x = 5, 10, 15 and 20 mol% were prepared by melt quenching method. The two phases of the GNCs samples, a glassy phase and PbTiO 3 nanoparticles/clusters phase, can be seen in the energy dispersive X-ray spectra and scanning electron microscopic micrographs. Fourier transformation infrared spectra of the GNCs samples exhibited bands due to triangular with NBO’s and tetrahedral borate groups. Additionally, the Ti 4+ ions exist in both TiO 4 and TiO 6 structural units while the Ti 3+ ions exist in TiO 6 structural units. The electron spin resonance (ESR) spectra of the GNCs samples exhibit two ESR signals, broad and narrow, corresponding to the Ti 3+ (3d 1 ) ions in both tetragonal deformed octahedral and in the other structural configuration, respectively. The optical transmission spectra of the GNCs samples exhibited three transmission bands, 3 Γ 5 → 2 Γ 3 , 2 B 2g → 2 B 1g and 2 B 2g → 2 A 1g transitions, in the visible region. The variation in optical band gap (E opt ) with increasing PbTiO 3 content were due to the conversion between BO 3 with NBOs and BO 4 units as well as the reduction of Ti 4+ to Ti 3+ ions in the GNCs matrix. These results demonstrate that the present GNCs may be used for practical applications such as optical devices.