酸化ウラン(VI)のソースを表示

{{翻訳中途|[[:en:Uranium trioxide]]|date=2016-1}}

{{chembox
| Watchedfields = changed
| verifiedrevid = 452010868
| Name = 酸化ウラン(VI)
| ImageFile = UO3 gamma lattice.png
| IUPACName = 酸化ウラン(VI)<br/>Uranium(VI) oxide
| OtherNames = 三酸化ウラン<br>Uranyl oxide<br/>Uranic oxide
|Section1={{Chembox Identifiers
| CASNo = 1344-58-7
| CASNo_Ref = {{cascite}}
}}
|Section2={{Chembox Properties
| Formula = UO<sub>3</sub>
| MolarMass = 286.29 g/mol
| Density = 5.5–8.7 g/cm<sup>3</sup>
| Appearance = 黄色-橙色の粉末
| Solubility = わずかに溶ける
| MeltingPt = ～200–650&nbsp;℃ (分解)
}}
|Section3={{Chembox Structure
| CrystalStruct = ''本文参照''
| SpaceGroup = ''I''4<sub>1</sub>/amd (''γ''-UO<sub>3</sub>)
| Coordination = 
}}
|Section4={{Chembox Thermochemistry
| DeltaHf = −1230&nbsp;kJ·mol<sup>−1</sup><ref name=b1>{{cite book| author = Zumdahl, Steven S.|title =Chemical Principles 6th Ed.| publisher = Houghton Mifflin Company| year = 2009| isbn = 0-618-94690-X|page=A23}}</ref>
| Entropy = 99&nbsp;J·mol<sup>−1</sup>·K<sup>−1</sup><ref name=b1/>
 }}
|Section7={{Chembox Hazards
| ExternalSDS = [http://www.ibilabs.com/UO3-MSDS.htm External MSDS]
| EUClass = 猛毒 ('''T+''')<br/>環境への危険性 ('''N''')
| RPhrases = {{R26/28}}, {{R33}}, {{R51/53}}
| SPhrases = {{S1/2}}, {{S20/21}}, {{S45}}, {{S61}}
| NFPA-H = 
| NFPA-F = 
| NFPA-R = 
| NFPA-S = 
| FlashPt = なし
| LD50 = 
| PEL = 
}}
|Section8={{Chembox Related
| OtherAnions = 
| OtherFunction = [[酸化ウラン(IV)]]<br/>[[八酸化三ウラン]]
| OtherFunction_label = [[ウラン]] [[酸化物]]s
| OtherCompounds =
}}
}}
'''酸化ウラン(VI)'''（さんかウラン ろく）または'''三酸化ウラン'''（さんさんかウラン）は[[ウラン]]の[[酸化物]]で、ウランの[[酸化数]]は +6 である。[[硝酸ウラニル]]を400 ℃に加熱することで得られる。結晶は[[多形|多形性]]があり、たとえば γ-UO<sub>3</sub> は黄色 - 橙色の粉末となる。

== 製法および用途 ==
酸化ウラン(VI)の生成法は3つある。そのうち2つは[[再処理工場|核燃料再処理]]と[[ウラン濃縮]]の際に用いられる。

[[ファイル:Uranium-trioxide-formation.png|500x500px|Methods of forming uranium trioxide]]
# [[八酸化三ウラン]](U<sub>3</sub>O<sub>8</sub>) を500 ℃で酸化する.<ref><cite class="citation journal">Sheft I, Fried S, Davidson N (1950). </cite></ref>。750 ℃以上では5気圧の[[酸素]]中でも酸化ウラン(VI)から八酸化三ウランへの分解が生じる<ref name="wheeler"><cite class="citation journal">Wheeler VJ, Dell RM, Wait E (1964). </cite></ref>
# [[硝酸ウラニル(VI)|硝酸ウラニル]] (UO<sub>2</sub>(NO<sub>3</sub>)<sub>2</sub>·6H<sub>2</sub>O) を400 - 600 ℃で加熱分解する。硝酸ウラニルは核燃料の再処理において発生する。燃料棒はウランを硝酸ウラニルとして[[プルトニウム]]や[[核分裂反応|核分裂生成物]]から分離するため[[硝酸]]に溶解される（[[PUREX法]]）。分離精製された硝酸ウラニルを加熱分解して得た酸化ウラン(VI)は、さらに水素で還元して酸化ウラン(IV)とし、燃料工場に回される。
# 重ウラン酸アンモニウム ((NH<sub>{{font|4|size=small}}</sub>)<sub>{{font|2|size=small}}</sub>U<sub>2</sub>O<sub>7</sub>)または重ウラン酸ナトリウム (Na<sub>2</sub>U<sub>2</sub>O<sub>7</sub>·6H<sub>2</sub>O) を500 ℃で加熱分解する。これらは[[ウラン濃縮]]の際に[[イエローケーキ]]から酸化ウラン(VI)に転換する際の中間物質である。酸化ウラン(IV)と[[四フッ化ウラン]]を経て[[六フッ化ウラン]][[酸化ウラン(IV)|を得る]]<ref><cite class="citation journal">Dell RM, Wheeler VJ (1962). </cite></ref>
酸化ウラン(VI)はゲル状にして処理工場間、特に[[鉱山]]から転換工場への輸送に用いられる。転換工場では、再処理工場で回収されたウラン酸化物は[[回収ウラン]]（reprocessed unanium, RepU）と呼ばれる<ref>http://www.world-nuclear.org/info/Nuclear-Fuel-Cycle/Transport/Transport-of-Radioactive-Materials/</ref>。

[[カメコ]]は[[カナダ]]の[[オンタリオ州]]ブラインドリバーにある世界最大級のウラン精製工場で高純度酸化ウラン(VI)を生産している。

ウランがケイ素分を多く含む水により腐食されると酸化ウラン(IV) および酸化ウラン(VI) <ref>Trueman ER, Black S, Read D, Hodson ME (2003) "Alteration of Depleted Uranium Metal" ''Goldschmidt Conference Abstracts,'' p. </ref> または[[コフィン石]]が生ずる<ref><cite class="citation journal">Guo X., Szenknect S., Mesbah A., Labs S., Clavier N., Poinssot C., Ushakov S.V., Curtius H., Bosbach D., Rodney R.C., Burns P. and Navrotsky A. (2015). </cite></ref>。純水中では1週間のうちに[[シェップ石]] (UO<sub>2</sub>)<sub>8</sub>O<sub>2</sub>(OH)<sub>12</sub>·12(H<sub>2</sub>O) が生じ<ref>[https://webmineral.com/data/Schoepite.shtml Schoepite]. </ref>、4ヶ月後には[[シュトゥット石]] (UO<sub>2</sub>)O<sub>2</sub>·4(H<sub>2</sub>O) が生ずる。水中で保管される使用済み核燃料の表面には、より安定した過酸化ウラニルからなる{{仮リンク|メタシュトゥット石|en|Metastudtite}}が生じることもある<ref><cite class="citation journal">Guo X., Ushakov S.V., Labs S., Curtius H., Bosbach D. and Navrotsky A. (2015). </cite></ref>。上記のような金属ウランの腐食に関する報告は、イギリス[[王立協会]]から出版されている<ref>Ander L, Smith B (2002) "[http://www.royalsoc.ac.uk/downloaddoc.asp?id=1182 Annexe F: Groundwater transport modelling]" ''The health hazards of depleted uranium munitions, part II'' (London: The Royal Society)</ref><ref>Smith B (2002) "[http://www.royalsoc.ac.uk/downloaddoc.asp?id=1183 Annexe G: Corrosion of DU and DU alloys: a brief discussion and review]" ''The health hazards of depleted uranium munitions, part II'' (London: The Royal Society)</ref>。

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== Health and safety hazards ==
Like all hexavalent uranium compounds, UO<sub>3</sub> is hazardous by inhalation, ingestion, and through skin contact. It is a poisonous, slightly radioactive substance, which may cause shortness of breath, coughing, acute arterial lesions, and changes in the chromosomes of [[白血球|white blood cells]] and gonads leading to congenital malformations if inhaled.<ref name="morrow"><cite class="citation journal">Morrow, PE, Gibb FR, Beiter HD (1972). </cite></ref><ref><cite class="citation journal">Sutton M, Burastero SR (2004). </cite></ref> However, once ingested, uranium is mainly toxic for the [[腎臓|kidneys]] and may severely affect their function.

== 構造 ==

=== 固体の結晶構造 ===
The only well characterized binary trioxide of any [[アクチノイド|actinide]] is UO<sub>3</sub>, of which several [[多形|polymorphs]] are known. Solid UO<sub>3</sub> loses O<sub>2</sub> on heating to give green-colored [[八酸化三ウラン|U<sub>3</sub>O<sub>8</sub>]]: reports of the decomposition temperature in air vary from 200–650&nbsp;°C. Heating at 700&nbsp;°C under H<sub>2</sub> gives dark brown [[酸化ウラン(IV)|uranium dioxide]] (UO<sub>2</sub>), which is used in [[MOX燃料|MOX]] [[核燃料|nuclear fuel]] rods.

==== Alpha ====
{| border="1" cellspacing="0" cellpadding="3"

| [[ファイル:UO3alphalattice.jpg|centre|138x138px]]
| ''The α (alpha) form: a layered solid where the 2D layers are linked by oxygen atoms (shown in red)''
| Hydrated uranyl peroxide formed by the addition of [[過酸化水素|hydrogen peroxide]] to an aqueous solution of [[硝酸ウラニル(VI)|uranyl nitrate]] when heated to 200–225&nbsp;°C forms an amorphous uranium trioxide which on heating to 400–450&nbsp;°C will form alpha-uranium trioxide.<ref name="wheeler"><cite class="citation journal">Wheeler VJ, Dell RM, Wait E (1964). </cite></ref> It has been stated that the presence of nitrate will lower the temperature at which the exothermic change from the [[アモルファス|amorphous]] form to the alpha form occurs.<ref><cite class="citation journal">Sato T (1963). </cite></ref>
|}

==== Beta ====
{| border="1" cellspacing="0" cellpadding="3"

| [[ファイル:UO3betalattice.jpg|centre|150x150px]]
| ''β (beta) UO<sub>3</sub>. This solid has a structure which defeats most attempts to describe it.''
| This form can be formed by heating ammonium diuranate, while P.C. Debets and B.O. Loopstra, found four solid phases in the UO<sub>3</sub>-H<sub>2</sub>O-NH<sub>3</sub> system that they could all be considered as being UO<sub>2</sub>(OH)<sub>2</sub>.H<sub>2</sub>O where some of the water has been replaced with ammonia.<ref><cite class="citation journal">Debets PC, Loopstra BO (1963). </cite></ref><ref><cite class="citation journal">Debets PC (1966). </cite></ref> No matter what the exact stoichiometry or structure, it was found that [[か焼|calcination]] at 500&nbsp;°C in air forms the beta form of uranium trioxide.<ref name="wheeler"><cite class="citation journal">Wheeler VJ, Dell RM, Wait E (1964). </cite></ref>
|}

==== Gamma ====
{| border="1" cellspacing="0" cellpadding="3"

| [[ファイル:UO3_gamma_lattice.jpg|centre|150x150px]]
| ''The γ (gamma) form, with the different uranium environments in green and yellow''
| The most frequently encountered polymorph is γ-UO<sub>3</sub>, whose [[X線結晶構造解析|x-ray structure]] has been solved from powder diffraction data. The compound crystallizes in the space group ''I4<sub>1</sub>/amd'' with two uranium atoms in the asymmetric unit. Both are surrounded by somewhat distorted octahedra of oxygen atoms. One uranium atom has two closer and four more distant oxygen atoms whereas the other has four close and two more distant oxygen atoms as neighbors. Thus it is not incorrect to describe the structure as [UO<sub>2</sub>]<sup>2+</sup>[UO<sub>4</sub>]<sup>2-&nbsp;</sup>, that is uranyl uranate.<ref><cite class="citation journal">Engmann R, de Wolff PM (1963). </cite></ref>
|}
{| border="1" cellspacing="0" cellpadding="3"

| [[ファイル:UO3_gamma_env1.jpg|centre|150x150px]]
| ''The environment of the uranium atoms shown as yellow in the gamma form''
| [[ファイル:UO3_gamma_rings.jpg|centre|150x150px]]
| ''The chains of U<sub>2</sub>O<sub>2</sub> rings in the gamma form in layers, alternate layers running at 90 degrees to each other. These chains are shown as containing the yellow uranium atoms, in an octahedral environment which are distorted towards square planar by an elongation of the [[自転|axial]] [[酸素|oxygen]]-[[ウラン|uranium]] bonds.''
|}

==== Delta ====
{| border="1" cellspacing="0" cellpadding="3"

| [[ファイル:UO3lattice.jpg|centre|150x150px]]
| ''The delta (δ) form is a [[立方晶|cubic]] solid where the oxygen atoms are arranged between the uranium atoms.''<ref><cite class="citation journal">M. T. Weller, P. G. Dickens, D. J. Penny (1988). </cite></ref>
|}

==== 高圧下 ====
高圧下では U<sub>2</sub>O<sub>2</sub> と U<sub>3</sub>O<sub>3</sub> の環状構造を含む<ref><cite class="citation journal">Siegel S, Hoekstra HR, Sherry E (1966). </cite></ref>
<ref>''Gmelin Handbuch'' (1982) '''U-C1,''' 129–135.</ref>。

==== 水和物 ====
[[ファイル:Uranium_Trioxides.jpg|right|thumb|酸化ウラン(VI)の水和物（左）と無水物（右）]]
酸化ウラン(VI)にはさまざまな水和物（たとえば六水和物 UO<sub>3</sub>·6H<sub>2</sub>O）が知られている.<ref name="wheeler"><cite class="citation journal">Wheeler VJ, Dell RM, Wait E (1964). </cite></ref>。

=== Bond valence parameters ===
It is possible by bond valence calculations<ref>[http://kristall.uni-mki.gwdg.de/softbv/references.html references]. </ref> to estimate how great a contribution a given oxygen atom is making to the assumed valence of uranium.<ref><cite class="citation journal">Zachariasen (1978). </cite></ref> Bond valence calculations use parameters which are estimated after examining a large number of crystal structures of uranium oxides (and related uranium compounds), note that the oxidation states which this method provides are only a guide which assists in the understanding of a crystal structure.

The formula to use is<center>
<math>
s = e^{-\frac{R-R_O}{B}}
</math>
</center>The sum of the ''s'' values is equal to the oxidation state of the metal centre.

For uranium binding to oxygen the constants R<sub>O</sub> and B are tabulated in the table below. For each oxidation state use the parameters from the table shown below.
{| style="margin: auto;"

!Oxidation state
!R<sub>O</sub>
!B
|-
| U(VI)
|2.08 Å
|0.35
|-
| U(V)
|2.10 Å
|0.35
|-
| U(IV)
|2.13 Å
|0.35
|}
It is possible to do these calculations on paper or software.<ref>[http://www.ccp14.ac.uk/ccp/web-mirrors/i_d_brown/ www.ccp14.ac.uk/ccp/web-mirrors/i_d_brown Free-download software]. </ref><ref>[http://www.ccp14.ac.uk/solution/bond_valence/index.html www.ccp14.ac.uk/solution/bond_valence/ Free-download software mirror]. </ref>

=== Molecular forms ===
While uranium trioxide is encountered as a polymeric solid under ambient conditions, some work has been done on the molecular form in the gas phase, in matrix isolations studies, and computationally.

==== Gas phase ====
At elevated temperatures gaseous UO<sub>3</sub> is in [[化学平衡|equilibrium]] with solid [[八酸化三ウラン|U<sub>3</sub>O<sub>8</sub>]] and molecular [[酸素|oxygen]].
:: 2 U<sub>3</sub>O<sub>8</sub>(s) + O<sub>2</sub>(g) [[File:Equilibrium.svg|link=|alt=is in equilibrium with|15x15px]]</span></span> 6 UO<sub>3</sub>(g)
With increasing temperature the equilibrium is shifted to the right. This system has been studied at temperatures between 900&nbsp;°C and 2500&nbsp;°C. The vapor pressure of monomeric UO<sub>3</sub> in equilibrium with air and solid U<sub>3</sub>O<sub>8</sub> at ambient pressure, about 10<sup>−5</sup>&nbsp;mbar (1 mPa) at 980&nbsp;°C, rising to 0.1&nbsp;mbar (10&nbsp;Pa) at 1400&nbsp;°C, 0.34&nbsp;mbar (34&nbsp;Pa) at 2100&nbsp;°C, 1.9&nbsp;mbar (193&nbsp;Pa) at 2300&nbsp;°C, and 8.1&nbsp;mbar (809&nbsp;Pa) at 2500&nbsp;°C.<ref><cite class="citation journal">Ackermann RJ, Gilles PW, Thorn RJ (1956). </cite></ref><ref><cite class="citation journal">Alexander CA (2005). </cite></ref>

==== Matrix isolation ====
Infrared spectroscopy of molecular UO<sub>3</sub> isolated in an argon matrix indicates a T-shaped structure ([[点群|point group]] ''C<sub>2v</sub>'') for the molecule. This is in contrast to the commonly encountered ''D<sub>3h</sub>'' [[分子対称性|molecular symmetry]] exhibited by most trioxides. From the force constants the authors deduct the U-O bond lengths to be between 1.76 and 1.79 [[オングストローム|Å]] (176 to 179 pm).<ref><cite class="citation journal">Gabelnick SD, Reedy GT, Chasanov MG (1973). </cite></ref>

==== Computational study ====
[[ファイル:Uranium-trioxide-Pyykko-3D-balls-B.png|right|thumb|200x200px|The calculated geometry of molecular uranium trioxide has C<sub>2v</sub> symmetry.]]
Calculations predict that the point group of molecular UO<sub>3</sub> is ''C<sub>2v</sub>'', with an axial bond length of 1.75 Å, an equatorial bond length of 1.83 Å and an angle of 161° between the axial oxygens. The more symmetrical ''D<sub>3h</sub>'' species is a saddle point, 49 kJ/mol above the ''C<sub>2v</sub>'' minimum. The authors invoke a second-order [[ヤーン・テラー効果|Jahn–Teller effect]] as explanation.<ref><cite class="citation journal">Pyykkö P, Li J (1994). </cite></ref>

=== Cubic Form of Uranium trioxide ===
The crystal structure of a uranium trioxide phase of composition UO2·82 has been determined by X-ray powder diffraction techniques using a Guinier-type focusing camera. The unit cell is cubic with a = 4·138 ± 0·005 kX. A uranium atom is located at (000) and oxygens at (View the MathML source), (View the MathML source), and (View the MathML source) with some anion vacancies. The compound is isostructural with ReO3. The U-O bond distance of 2·073 Å agrees with that predicted by Zachariasen for a bond strength S = 1.<ref>http://www.sciencedirect.com/science/article/pii/002219025580036X</ref>
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== 反応 ==
酸化ウラン(VI)は400 ℃で[[ジクロロジフルオロメタン]]と反応して[[四フッ化ウラン]]となり、[[塩素]]、[[ホスゲン]]、[[二酸化炭素]]を生じる。[[トリクロロフルオロメタン]]との反応では二酸化炭素の代わりに[[四塩化炭素]]が生じる。これは一般には化学的に安定と言われているハロゲン化度の高いフロンの分解反応である<ref><cite class="citation journal">Booth HS, Krasny-Ergen W, Heath RE (1946). </cite></ref>
: <chem>2CF2Cl2\ + UO3 -> UF4\ + CO2\ + COCl2\ + Cl2</chem>
: <chem>4CFCl3\ + UO3 -> UF4\ + 3COCl2\ + CCl4\ + Cl2</chem>

酸化ウラン(VI)は[[リン酸トリブチル]]と[[テノイルトリフルオロアセトン]]を含んだ[[超臨界]]二酸化炭素に超音波をあてることで溶解する<ref><cite class="citation journal">Trofimov TI, Samsonov MD, Lee SC, Myasoedov BF, Wai CM (2001). </cite></ref>。

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=== Electrochemical modification ===
The reversible insertion of [[マグネシウム|magnesium]] cations into the [[結晶構造|lattice]] of uranium trioxide by [[サイクリックボルタンメトリー|cyclic voltammetry]] using a [[グラファイト|graphite]] electrode modified with microscopic particles of the uranium oxide has been investigated. This experiment has also been done for U<sub>3</sub>O<sub>8</sub>. This is an example of [[電気化学|electrochemistry]] of a solid modified [[電極|electrode]], the experiment which used for uranium trioxide is related to a carbon paste electrode experiment. It is also possible to reduce uranium trioxide with [[ナトリウム|sodium]] metal to form sodium uranium oxides.<ref><cite class="citation journal">Dueber, R. E. (1992). </cite></ref>

It has been the case that it is possible to insert [[リチウム|lithium]]<ref><cite class="citation journal">Dickens PG, Lawrence SD, Penny DJ, Powell AV (1989). </cite></ref><ref><cite class="citation journal">Dickens, P.G. Hawke, S.V. Weller, M.T. (1985). </cite></ref><ref><cite class="citation journal">Dickens, P.G. Hawke, S.V. Weller, M.T. (1984). </cite></ref> into the uranium trioxide lattice by electrochemical means, this is similar to the way that some [[二次電池|rechargeable]] [[リチウムイオン二次電池|lithium ion batteries]] work. In these rechargeable cells one of the electrodes is a metal oxide which contains a metal such as [[コバルト|cobalt]] which can be reduced, to maintain the electroneutrality for each electron which is added to the electrode material a lithium ion enters the lattice of this oxide electrode.

=== Amphoterism and reactivity to form related uranium(VI) anions and cations ===
Uranium oxide is [[両性 (化学)|amphoteric]] and reacts as [[酸|acid]] and as a [[塩基|base]], depending on the conditions.
; As an acid

: UO<sub>3</sub> + H<sub>2</sub>O → UO2−<br>4<span class="chemf" style="white-space: nowrap;"></span> + 2 H<sup>+</sup>
Dissolving uranium oxide in a strong [[塩基|base]] like [[水酸化ナトリウム|sodium hydroxide]] forms the doubly negatively charged uranate [[イオン|anion]] (UO<span style="text-align: left; line-height: 1.2em; font-size: 85%; margin-bottom: -0.3em; vertical-align: -0.4em; display: inline-block;">2−<br>
4</span>). Uranates tend to concatenate, forming diuranate, U<span style="text-align: left; line-height: 1.2em; font-size: 85%; margin-bottom: -0.3em; vertical-align: -0.4em; display: inline-block;"><br>
2</span>O<span style="text-align: left; line-height: 1.2em; font-size: 85%; margin-bottom: -0.3em; vertical-align: -0.4em; display: inline-block;">2−<br>
7</span>, or other poly-uranates.
Important diuranates include ammonium diuranate ((NH<sub>4</sub>)<sub>2</sub>U<sub>2</sub>O<sub>7</sub>), sodium diuranate (Na<sub>2</sub>U<sub>2</sub>O<sub>7</sub>) and
magnesium diuranate (MgU<sub>2</sub>O<sub>7</sub>), which forms part of some [[イエローケーキ|yellowcakes]]. It is worth noting that uranates of the form M<sub>2</sub>UO<sub>4</sub> do ''not'' contain UO<span style="text-align: left; line-height: 1.2em; font-size: 85%; margin-bottom: -0.3em; vertical-align: -0.4em; display: inline-block;">2−<br>
4</span> ions, but rather flattened UO<sub>6</sub> octahedra, containing a uranyl group and bridging oxygens.<ref><cite class="citation book">Cotton, Simon (1991). </cite></ref>
; As a base

: UO<sub>3</sub> + H<sub>2</sub>O → UO2+<br>2<span class="chemf" style="white-space: nowrap;"></span> + 2 OH<sup>−</sup>
Dissolving uranium oxide in a strong acid like [[硫酸|sulfuric]] or [[硝酸|nitric acid]] forms the double positive charged [[ウラニルイオン|uranyl]] [[イオン|cation]]. The [[硝酸ウラニル(VI)|uranyl nitrate]] formed (UO<sub>2</sub>(NO<sub>3</sub>)<sub>2</sub>·6H<sub>2</sub>O) is soluble in [[エーテル (化学)|ethers]], [[アルコール|alcohols]], [[ケトン|ketones]] and [[エステル|esters]]; for example, [[リン酸トリブチル|tributylphosphate]]. This solubility is used to separate uranium from other elements in [[再処理工場|nuclear reprocessing]], which begins with the dissolution of [[核燃料|nuclear fuel]] rods in [[硝酸|nitric acid]]. The [[硝酸ウラニル(VI)|uranyl nitrate]] is then converted to uranium trioxide by heating.

From [[硝酸|nitric acid]] one obtains [[硝酸ウラニル(VI)|uranyl nitrate]], ''trans''-UO<sub>2</sub>(NO<sub>3</sub>)<sub>2</sub>·2H<sub>2</sub>O, consisting of eight-coordinated uranium with two bidentate nitrato ligands and two water ligands as well as the familiar O=U=O core.

== Uranium oxides in ceramics ==
UO<sub>3</sub>-based ceramics become green or black when fired in a reducing atmosphere and yellow to orange when fired with oxygen. Orange-coloured Fiestaware is a well-known example of a product with a uranium-based glaze. UO<sub>3</sub>-has also been used in formulations of [[琺瑯|enamel]], [[ウランガラス|uranium glass]], and [[磁器|porcelain]].

Prior to 1960, UO<sub>3</sub> was used as an agent of crystallization in crystalline coloured glazes. It is possible to determine with a [[ガイガー＝ミュラー計数管|Geiger counter]] if a glaze or glass was made from UO<sub>3</sub>.
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== 脚注 ==
{{Reflist|2}}

{{デフォルトソート:さんかうらん6}}
[[Category:酸化物]]
[[Category:ウランの化合物]]
[[Category:ウラニル化合物]]