Effect of Silver Content on the Crystalline Phase and Microstructure of TiO2 Coating Deposited on Unglazed Ceramics Tile

Abstract

The synthesis of Ag-TiO₂ coating using AgNO₃ precursor is expected to give the properties as pure as Ag nanoparticles. Commonly, high concentration of Ag attributed to agglomeration of silver species and reduction to Ag⁰ particles on TiO₂ surface. In contrast, at lower concentration, Ag species exist as AgO, Ag₂O and Ag⁰. Hence, the exact amount of Ag, which can effectively control the particle growth and agglomeration, surface area, thermal stability and band gap of the TiO2 coating, are still vague and stated differently. In the present study, the effect of Ag content on the phase transformation and surface morphology of Ag-TiO₂ coating were reported. TiO₂ sol were prepared by incorporating Ag at 2.5, 5 and 7.5 mol % and deposited on unglazed ceramic tiles thru five times dip coating. The deposited Ag-TiO₂ coatings were heat treated at 500 °C for 1 hour soaking time. XRD analyses revealed that the deposited Ag-TiO₂ coating consists of anatase, rutile, Ag₂O and metallic Ag. Almost all the coating surfaces illustrated cracks. Increased Ag content lead to presence of tiny particles on the surfaces and EDX spectrum revealed the presence of Ti, O and metallic Ag particles. However, at the addition of 5 mol % Ag_, there was no metallic Ag presence and a dense coating with the lowest thickness of ±11.4µm is observed.