Photo-acoustic Study of Zircon-based Ceramic Pigments and Glasses Containing High Concentrations of Copper and Cobalt

Zircon stains for the ceramics industry have been produced commercially since 1949. At present the commercial stains are mainly zircon (ZrO2.SiO2) doped with vanadium, praseodymium or iron to produce blue, yellow or pink colours respectively. A research programme is in progress to study the factors controlling the colours of these zircon-based glaze stains and photo-acoustic spectroscopy has been used to monitor the colours of stains prepared by different routes. Spectra of coral pink tiles reveal a broad absorption between 600 nm and 350 nm which is yet to be identified. A blue glaze has a spectrum which suggests the presence of V4+ but the yellow glaze has a sharp cut-off near 470 nm which is quite uncharacteristic of the spectrum expected from Pr3+. Single crystal specimens of the doped zircon are being prepared and these too will be examined photo-acoustically. An attempt will also be made to obtain transmission measurements.