| Abstract [eng] |
X-ray diffraction analysis (XRD), infrared (IR) spectroscopy and scanning electron microscopy have been used for the characterization of cobalt-based pigments (Kremer Pigmente) and their lead-based glazes. It was also demonstrated that XRD analysis could be successfully used for the identification of cobalt pigments cobalt violet brilliant light CoNH4PO4•H2O, cobalt blue light, cerulean blue, cobalt green bluish CoO·ZnO in their glazes. However, only non-oxide cobalt pigments cobalt yellow [K3(Co(NO2)6]•3H2O, cobalt violet brilliant light and cobalt violet dark Co3(PO4)2 could be determined in their glazes using IR spectroscopy. The similarity of all SEM images of cobalt-based glazes let us to conclude, that the main morphological features of glazes are not dependent on the nature of cobalt pigment. The single phase cobalt violet light brilliant pigment has been synthesized using a simple co-precipitation approach. The characteristics of the obtained product were compared with those of a commercial sample purchased from Kremer Pigmente. For the first time to our knowledge, it was demonstrated that the characteristic Si-O absorption band at 812 cm-1 could be successfully used as indicator in the evaluation of molar ratio of CoO and SiO2 in their mixture. The novel method for the determination of SiO2 in physical mixtures of CoO ir SiO2 (in the range 9,1-50 %) or blue cobalt smalt pigment (CoO×nSiO2) (in the range 20-50 %) by FTIR spectroscopy is suggested. New cobalt-based pigments having spinel crystal structure such as CoAl2O4, CoCr2O4 and similar systems in which aluminium was partially replaced by neodymium CoAl1.75Nd0.25O4, CoAl1.5Nd0.5O4, CoAlNdO4 have been synthesized using an aqueous sol-gel chemistry technique. The obtained glazes showed sufficient colour characteristics. For the first time, novel perovskite structure compounds NdCoO3, substituted neodymium cobaltates-aluminates (NdCo0.75Al0.25O3, NdCo0.5Al0.5O3, NdCo0.25Al0.75O3) and mixed neodymium-yttrium analogues (Nd0.5Y0.5)CoO3, (Nd0.5Y0.5)Co0.75Al0.25O3, (Nd0.5Y0.5)Co0.5Al0.5O3, (Nd0.5Y0.5)Co0.25Al0.75O3 have been synthesized by sol-gel synthesis method. The obtained glazes using these novel cobalt pigments showed bluish colour which intensity depends on the chemical composition of mixed-metal cobaltates. It was demonstrated, that the same sol-gel chemistry approach can not be used for the preparation of erbium cobaltate. The XRD pattern of the obtained synthesis product showed formation only two separate oxides Er2O3 and Co3O4. |
