Effects of firing temperatures and compositions on the formation of nano particles in lustre layers on a lead-alkali glaze

Iznik tiles were reproduced in laboratory-controlled conditions using two different lustre pastes at the firing temperatures of 615 °C and 650 °C. The lustre layers were characterised by WDXRF, XRD, SEM, UV–vis–NIR, XPS, HRTEM-EDS techniques. They comprised nanoparticles of silver and/or copper which appeared either as Cu₂O or Cu⁺, Cu²⁺ dissolved in the glassy matrix by ionic exchange between Ag⁺ and/or Cu⁺ and alkaline ions (Na⁺ and/or K⁺) from the glaze, diffusion of the metal ions followed by nucleation and growth in a reducing atmosphere. Metallic silver nanoparticles grew with increasing temperature, as observed from absorption spectra and TEM micrographs. As the nanoparticle size increased, the surface plasmon resonance was slightly blue-shifted for silver. TEM images revealed the silver nanoparticles in sizes varying between 3 nm and 13 nm depending on temperature and paste composition. These results are compatible with calculations based on UV–visible absorbance spectra.