ZrOCl_2水溶液の加水分解により生成する水和ジルコニア微粒子の結晶相に及ぼすpHの影響

概要

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The crystal structure of hydrous-zirconia fine particles, produced by the hydrolysis of ZrOCl_2 in aqueous solutions with and without an addition of NH_4OH or HCl, was investigated using X-ray diffraction(XRD) and Raman spectroscopy. Main emphasis was placed to clarify the effects of pH on the crystal formation. The XRD patterns of hydrous zirconias synthesized at pH-values below about 1 were similar to those observed for monoclinic crystalline zirconia. At pH-values greater than about 1, the diffraction line assigned to the 111 reflection of the tetragonal or cubic phases was observed, in addition to those of the monoclinic phase. Raman spectra measurements revealed that the diffraction line agreed with that of tetragonal crystalline zirconia. The fraction of the tetragonal phase showed a tendency to increase as the pH increased. When the pH was attained to around neutrality, amorphous hydroxide formed. These experimental results indicated that the crystal phase in hydrous zirconia is primarily governed by the concentration of H^+ ions(pH)produced during hydrolysis. The crystal-formation mechanism for hydrous-zirconia fine particles was determined on the basis of the present experimental results.
社団法人日本セラミックス協会の論文
1998-12-01