Optical Properties of (V, Pr)-doped ZrSiO₄Green Pigments

Synthesis of zircon pigments from rice husk ash and their performance in ceramic glaze

“…From the Hedvall effect, it is likely that onset crystallization of SiO2 at higher than 700℃ might trigger the reactions among the starting precursors. This temperature of 700℃ was also stated by Pyon et al [15] to induce initiation of zircon crystal formation. As the temperature Table 1.…”

“…The V-doped zircon sample yielded a broad peak with a maximum of reflectance in the 500 nm range with a highest degree of absorption in the 640 nm range (Figure 9(a)). Ardizzone et al [9] and Pyon et al [15] reported spectra with relatively similarity to what was obtained in this study; the first authors employed a reflectance mode whereas the latter author an absorbance mode. The presence of V 5+ could be ruled out given the fact that no reflectance peak at approximately 530 nm was observed [9].…”

“…A careful, slow scan did not reveal an amorphous halo as observed in an amorphous silicate glass (data not shown). Investigations using RHA with NaF as a flux by other researchers did not demonstrate this cristobalite peak but displayed only monoclinic ZrO2 as a secondary phase when fired at or above 1000℃ [15,16]. Pyon et al [15] showed that NaVO3 formed first as an intermediate phase with the reaction between SiO2 and m-ZrO2 starting at 700℃.…”

“…Investigations using RHA with NaF as a flux by other researchers did not demonstrate this cristobalite peak but displayed only monoclinic ZrO2 as a secondary phase when fired at or above 1000℃ [15,16]. Pyon et al [15] showed that NaVO3 formed first as an intermediate phase with the reaction between SiO2 and m-ZrO2 starting at 700℃. They claimed that the Hedvall effect with enhanced reactivity during phase transitions was responsible for maximization of the reaction rate toward zircon formation.…”

“…Extraction of pure SiO2 from RHA using alkali and acidic treatment is a laborious and costly process and could have made this alternative source not being advantages to other sources [14]. Several studies on zircon pigment synthesis used RHA without chemical extraction but the chromophores were still limited to vanadium and praseodymium [2,15,16].…”