RARE EARTH OXIDE POWDER

To provide a rare earth oxide fine powder capable of: being easily dispersed without an intense crushing process; forming a thin coating film; or obtaining a highly dispersed slurry without the use of a dispersing agent, thereby maintaining a stable transparency.SOLUTION: The present invention relates to powder of oxides of a rare earth element other than Ce, which satisfies (a) or (b). (a) A primary particle diameter is 10 to 60 nm, satisfying (I) or (II). (I) D100 measured by ultrasonic dispersion is 1 to 10 μm. (II) When the true density is ρ, a difference between porosity PAD(%) calculated from the initial bulk density AD and porosity PTD(%) calculated from the tapped bulk density TD is 2.0 to 5.0%. PAD=(1-AD/ρ)×100 PTD=(1-TD/ρ)×100 (b). A primary particle size is 10 nm or larger and smaller than 100 nm, satisfying (III) and (IV). (III) A value obtained by multiplying a pore volume of 0.005 to 100 μm in pore diameter by the true density is 3 to 14. (IV) A value obtained by multiplying a pore volume of 5 to 50 nm in pore diameter by the true density is 0 to 2.0.SELECTED DRAWING: None 【課題】強度の解砕処理がなくても容易に分散でき、薄膜の塗膜が形成可能、或いは、分散剤を用いずに高分散スラリーが得られ透明度を安定維持できる、希土類酸化物微粉末を提供する。【解決手段】（ａ）又は（ｂ）を満たす、Ｃｅ以外の希土類元素の酸化物の粉末。（ａ）一次粒子径が１０～６０ｎｍで、（Ｉ）又は（II）を満たす。（Ｉ）超音波分散して測定したＤ100が１～１０μｍ。（II）真密度をρとしたとき、初期嵩密度ＡＤから算出される空隙率ＰAD（％）と、タップ嵩密度ＴＤから算出される空隙率ＰTD（％）の差が２．０～５．０％。ＰAD＝（１－ＡＤ／ρ）×１００ＰTD＝（１－ＴＤ／ρ）×１００（ｂ）一次粒子径が１０ｎｍ以上１００ｎｍ未満で、（III）及び（IV）を満たす。（III）細孔直径０．００５～１００μｍの細孔容積に真密度を掛けた値が３～１４。（IV）細孔直径５～５０ｎｍの細孔容積に真密度を掛けた値が０～２．０。【選択図】なし