Role of titanium ions on the physical and structural properties of calcium zinc bismuth phosphate glass ceramics

Abstract

The transparent glass ceramics of composition 10CaF2–20ZnO–(15–x)Bi2O3–55P2O5: xTiO2 (0≤x≤4) were prepared by melt quenching followed by heat treatment. The prepared samples were characterized by X-ray diffraction, differential thermal analysis and scanning electron microscopy. These studies have revealed that the samples contain well defined randomly distributed crystalline phases with the complexes of Ti4+ and Ti3+ ions. Spectroscopic studies viz., optical absorption, electron paramagnetic resonance, Fourier transform infrared and Raman were also carried out on these glass ceramics. The results of optical absorption and electron paramagnetic resonance studies revealed that part of the titanium ions exist in Ti3+ state that occupy the tetragonally distorted octahedral sites in the glass ceramic network and these ions are found to increase with an increase in the content of nucleating agent TiO2. Fourier transform infrared and Raman studies indicating the formation of TiO6 structural units along with cross linkages viz., P–O–Bi, P–O–Ti. But when TiO2 is present in the larger quantities, the Π-bond of P=O may be ruptured by TiO4 structural units which may cause the creation of new non-bridging oxygen ions facilitating the formation of [TiO6/2]2− structural units also. Therefore, the analysis of spectroscopic studies indicating that the glass ceramics contain greater than 2mol% of TiO2 is suitable for semiconducting applications.