Titanium-zinc polycitrate precursor: Influence of thermal treatment on structural, thermal, optical characteristics of zinc titanates

Abstract

Viewing the future application as luminescent filler for security paint we synthesized and characterized titanium-zinc poly(ethylene citrate) before and after thermal treatment. The polymeric precursor was obtained by sol-gel method at 80–120 °C using zinc acetate/titanium (IV) isopropoxide as parent reagents and it was thermally treated (600–1100 °C), during 5 h. Poly (ethylene citrate) 13carbon nuclear magnetic resonance (13CNMR) spectrum revealed heterogeneous catenation with variable microstructures. Its fluorescence spectrum showed band emission at visible region while wide angle x-ray diffraction (WAXD) depicted amorphous material. When poly(ethylene citrate) was submitted to calcination, the oxides phase compositions were dependent on the temperatures confirmed by Raman spectroscopy and WAXD. The oxides thermal stability increased according to the thermal treatment and phase transformations were seen. SEM images showed coexistence of the hexagonal and star crystalline morphologies at the highest calcination temperature. The fluorescence spectra revealed emission around 420 nm at the highest calcination temperature. Oxides diffuse reflectance spectra presented sigmoid shape. The bands appeared at UVA (410-315 nm) and UVB (330-270 nm) and shifted to higher wavelength according to the calcination temperatures. The photoluminescence intensity of the zinc titanate treated at 1100 °C is the most suitable for application as filler in security paints.