Effect of sintering temperature on the developed crystalline phases, optical and electrical properties of 5ZnO-2TiO2- 3P2O5 glass

Glass of the composition 5ZnO-2TiO2- 3P2O5 was prepared by the melt-quenching technique. The prepared samples were heat-treated at the nucleation (625 °C) and crystallization (875 °C) temperatures for different soaking times. SEM, XRD, UV-Vis, DSC and electrical measurements were used. Ti(PO4) and Zn3(PO4)2 phases were formed at the nucleation temperature; while, Ti5O4(PO4)4 and α-Zn2P2O7 phases were observed at the crystallization temperature. Long soaking time caused color fading or formation of opaque white samples due to the decrease of Ti3+ ions or increase of Ti4+ ions, respectively. The formation of Ti3+ ions causes a development of violet color with absorption bands in the range 400-800 nm. SEM suggested that prolonged heating at the crystallization temperature caused disintegration of the formed phases. The electrical conductivities of the studied samples at the low and high measuring temperatures occur via electrons revealing their suitability to be applied as semiconductors. The values of σac and dielectric constant ε′ increase with rising the sintering temperature. The ε′ of the as-prepared sample (19.23) is increased to 152.45 or 189.11 when heat-treated at the nucleation temperature for 4 h and at crystallization temperature for 15 min, respectively. Samples of high ε′ values represent promising candidates for energy storage in electronic devices.