Papers by Keyword: YAP

Abstract: The geometry optimization, formation energy, Mulliken populations, and density of states of YAP (YAlO₃) crystal are studied by using first-principles method based on density functional theory. The optimal lattice parameters of YAP crystal are in good accordance with experimental results reported. The calculated formation energy (-3.73eV) indicates the excellent structural stability of YAP crystal. The obtained Mulliken charge populations of O, Al and Y atoms and their deviations from the formal ones, as well as overlap populations show YAP crystal is a mixed bond material with stronger ionic and weaker covalent bonds, which is attributed to the hybridization of atomic orbitals. The comprehensive effect of various interactions in the system makes YAP crystal more stable.

Abstract: Double yttrium-aluminium oxide with perovskite structure (YAP) doped with chromium(III) ions seems to be a promising material for red pigments for new ceramic bodies and glazes. The aim of the present paper was to examine the influence of the precursors morphology on colour properties of the YAP pigments. Two kinds of aluminium hydroxide powders were used, fine- and coarse-grained. The fine Al(OH)3 powder was amorphous with D50=4.58 µm and the coarse one was crystalline gibbsite with D50=42.4 µm. It was stated that using of aluminium hydroxide powders of different morphology led to substantial differences in phase composition of the final materials. Using coarse-grained aluminium hydroxide powder caused formation of over 95 wt% of YAP phase whereas the pigments prepared with amorphous aluminium hydroxide contain significant amounts of other phases in the Y2O3-Al2O3 system. The differences in phase compositions resulted in differences in colour properties of the pigments.