X-RAY DIFFRACTION STUDY FOR DETECTION OF THE OPTIMUM CONDITIONS IN THE PPREPARATION OF CELSIAN AND Ni-CELSIAN GLAZE PIGMENT

M.Z. Mostafa, A.M. Abou El-Soud, S.M. Hammad and Ahmed El-Maghrapy

Hence, two polymorphs of barium feldspar compound are known, namely the high temperature form (hexacelsian) and the low temperature one (monoclinic, celsian). The trials were made to get the optimum conditions concerning iring schedule (temperature and time) and meniralizer addition for the preparation of monoclinic celsian which is the suitable phase for the formation of coloured ciramic spinel pigments.

In the present work Ni-celsian pigments have been synthesized from barium carbonate, alumina, silica and using the chemically pure Li₂Co₃ as a mineralizer. The X-ray diffractograms detect the high rate of celsian formation at 1200^oC by firing for 4 hrs in presence of 4 mole % Li₂Co₃ at which the transformation of hexacelsian to celsian was enhanced. The solid state reaction between the starting materials reached its optimum rate by using their particle sizes less than 67 mm.

Replacement of nickel for barium in the celsian structure was done effectively using the added chromophore in the form of NiO. The substitution of BaO by NiO is complete up to about 0.4 - 0.5 moles. Pigments obtained exhibits blue-green to near violet, blue green and green colours which determined as the proportion of nickel increase.

The study of the X-ray diffraction for the synthesized pigments gave information about the phases formed and the limits of substitution in the structure.