Color modification of (Al, Cr)2O3 pigments by Mg addition
Kato Masahiro; Unuma Hidero; Suzuki Suguru; Takahasi Minoru
Abstract:Addition of Mg into (Al, Cr)2O3 pigments significantly varied their colors. The Mg added pigments consisted of (Al, Cr)2O3 corundum phase (C phase) and Mg(Al, Cr)2O 4 spinel phase (S phase). In order to obtain data for the evaluation of the Cr contents in the C and S phases, (Al sub 1 sub minus sub xCr sub x)2O3 corundum and Mg(Al sub 1 sub minus sub xCr sub x)2O 4 spinel both with x ranging from 0 to 1 were synthesized, and their lattice constants were measured by the XRD method. Lattice constants of the C phase in the pigments prepared from (0.9 x) mol Al2O3, 0. mol Cr2O3 and x mol MgCO3 were independent of the Mg content, and the Cr concentration of the C phase in each pigment was determined to be 10 mol%. On the other hand, a lattice constant of the S phase decreased with the increase in the Mg content. Using the lattice constant data of the synthesized spinel and corundum, it was shown that the Cr content of the S phase decreased with the increase in the Mg content. It was concluded that the color variations caused by the Mg addition into (Al, Cr)2O3 pigments were attributable to changes of the Cr content of the S phase. Key Words:pigment, Cr3+ content, spinel, corundum, lattice constant, absorbance