| 摘要 |
PROBLEM TO BE SOLVED: To obtain alumina particles consisting of hexagonally lamellar α-alumina single crystal, suitable as a base material for extender pigments for cosmetic use, inorganic pigments (esp. pearl pigments) for coating use, or as a ceramic material. SOLUTION: The objective alumina particles each 0.2-15μm in diameter and 15-50 in aspect ratio are obtained by adding a crystallization-suppressing agent containing at least phosphate ions to aluminum hydroxide or alumina hydrate followed by conducting a hydrothermal synthesis pref. at >=350 deg.C under a pressure of 50-200atm at a rate of temperature rise of 5-0.3 deg.C/min. It is preferable that the amount of the phosphate ions to be added be 3.0×10<-3> to 2.5×10<-2> mol per mol of the aluminum hydroxide or alumina hydrate whose particle diameter be 0.1-5.0μm. |
