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

Abstract

Glass-nanocomposites (GNCs) samples of composition [(100−x) Li2B4O7–xPbTiO3] 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 PbTiO3 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 Ti4+ ions exist in both TiO4 and TiO6 structural units while the Ti3+ ions exist in TiO6 structural units. The electron spin resonance (ESR) spectra of the GNCs samples exhibit two ESR signals, broad and narrow, corresponding to the Ti3+ (3d1) 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, 3Γ5 → 2Γ3, 2B2g → 2B1g and 2B2g → 2A1g transitions, in the visible region. The variation in optical band gap (Eopt) with increasing PbTiO3 content were due to the conversion between BO3 with NBOs and BO4 units as well as the reduction of Ti4+ to Ti3+ ions in the GNCs matrix. These results demonstrate that the present GNCs may be used for practical applications such as optical devices.