「」至此。關於硼的其他氧化物，請見「**一氧化二硼**」。

**三氧化二硼**（化学式：B2O3）又称**氧化硼**，是硼最主要的氧化物。它是一种白色蜡状固体，一般以无定形的状态存在，很难形成晶体，但在高强度退火后也能结晶。它是已知的最难结晶的物质之一。

结构
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玻璃状氧化硼（g-B2O3）很可能是一种由许多三角形BO3单元通过共用氧原子部分有序连接而成的网络结构，其中以硼氧相间的六元环B3O3占优势。该六元环中，硼原子为三配位，氧原子为二配位。该玻璃体在325－450 °C时软化，其密度随受热情况而有一个变化范围。加热时，玻璃体氧化硼结构中的无序度增加。超过450 °C时会产生有极性的－B＝O基。高于1000 °C时，氧化硼蒸气则全部由B2O3单体组成，其结构为角形的 O＝B－O－B＝O。

常压下使液态的氧化硼在200－250 °C范围内结晶，可以形成普通的六方晶系氧化硼（α-B2O3），其结构（见右图）几乎全部由三角形的BO3单元组成。

在22000atm和400 °C时，α-B2O3转变为高温高压型的单斜晶体β-B2O3。该转变过程类似于石英在高压下到柯石英的转化。除此之外，β-B2O3也可以由液态氧化硼在40000atm和600 °C时结晶得到。

β-B2O3的体积模量很大（K = 180 GPa）。g-B2O3和β-B2O3的维氏硬度分别为1.5GPa和16GPa。

制备
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虽然硼在空气和氧气中燃烧都可以直接产生三氧化二硼，但三氧化二硼主要是通过硼酸脱水制取的。在200－400 °C对硼酸真空脱水，可以得到非常干燥的三氧化二硼。如果在大气中脱水，即使加热到1000 °C，也很难去除最后剩下的痕量水。

{\displaystyle {\rm {H\_{3}BO\_{3}\rightarrow HBO\_{2}+H\_{2}O\,}}}
{\displaystyle {\rm {2HBO\_{2}\rightarrow B\_{2}O\_{3}+H\_{2}O\,}}}
硼酸则可通过硼砂和硫酸共热反应制取。

化学性质
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氧化硼是酸性氧化物，熔融时可以溶解许多碱性的金属氧化物，生成有特征颜色的玻璃状硼酸盐和偏硼酸盐（玻璃）。这是硼砂珠试验定性鉴别金属的原理。例如：

{\displaystyle {\rm {CuO+B\_{2}O\_{3}\rightarrow Cu(BO\_{2})\_{2}\,}}}（蓝色）
{\displaystyle {\rm {Fe\_{2}O\_{3}+3B\_{2}O\_{3}\rightarrow 2Fe(BO\_{2})\_{3}\,}}}（黄色）
氧化硼可以被碱金属、铝和镁还原为单质硼：

{\displaystyle {\rm {B\_{2}O\_{3}+3Mg\rightarrow 2B+3MgO\,}}}
反应后用盐酸处理反应混合物，MgO、B2O3和Mg溶于盐酸，过滤后得到粗硼。氧化硼在高温时不能为碳还原（高温下可以形成碳化硼）。高温下氧化硼与碳和氯气反应，可以得到三氯化硼：

{\displaystyle {\rm {B\_{2}O\_{3}+3C+3Cl\_{2}\rightarrow 2BCl\_{3}+3CO\,}}}
600 °C时，氧化硼与氨反应可以得到氮化硼（BN），与氢化钙反应则得到六硼化钙（CaB6）。

氧化硼是硼酸的酸酐，溶于水时会放出大量热生成偏硼酸和硼酸：

{\displaystyle {\rm {B\_{2}O\_{3}(s)+H\_{2}O(g)\rightarrow 2HBO\_{2}(g)\,}}}， {\displaystyle {\rm {\Delta H^{o}=-199.2kJ/mol\,}}}
{\displaystyle {\rm {B\_{2}O\_{3}+3H\_{2}O\rightarrow 2H\_{3}BO\_{3}\,}}}

应用
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氧化硼可以用作：

* 制取其他硼化合物（如碳化硼）的原料；
* 制造硼矽酸鹽玻璃（英语：）的原料；
* 有机合成中的酸性催化剂；
* 搪瓷、陶瓷釉料的助熔剂；
* 玻璃纤维生产过程中的添加剂；
* 制造化合物半导体（如砷化镓、磷化镓、砷化铟）时的液封剂等。

参见
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* 硼酸
* 一氧化二硼
* 低氧化硼

参考资料
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1. ↑  Eckert, H. Prog. *NMR Spectrosc.*, 24 (1992) 159-293.
2. ↑  S.-J. Hwang, C. Femandez, J.P. Amoureux, J. Cho, S.W. Martin & M. Pruski. "Quantitative study of the short range order in B,O, and B,S, by MAS and two-dimensional triple-quantum MAS 11B NMR" *Solid State Nuclear Magnetic Resonance* 8 (1997) 109-121
3. ↑  G.E. Gurr, P.W. Montgomery, C.D. Knutson, B.T.Gorres "The Crystal Structure of Trigonal Diboron Trioxide" Acta Cryst. B26 (1970) 906-915
4. ↑  V. V. Brazhkin et al. "Structural transformations in liquid, crystalline and glassy B2O3 under high pressure" JETPh Lett. 78 (2003) 845 （页面存档备份，存于）
5. 1 2  V. A. Mukhanov, O. O. Kurakevich, and V. L. Solozhenko "On the Hardness of Boron (III) Oxide" of Superhard Materials 30 (2008) 71
6. ↑  Pradyot Patnaik. *Handbook of Inorganic Chemicals*. McGraw-Hill, 2002, ISBN 0-07-049439-8

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* 论
* 编
**氧化物** |
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| --- | --- | --- | --- | --- |
| H2OH2O2H2O3 |  |  |  | He |
| Li2O | BeO | B2O3B2O | COCO2CO*x* | N2ONONO2NO*x* | **O2**O3 | OF2O2F2 | Ne |
| Na2O | MgOMgO2 | Al2O3 | SiOSiO2 | POP2O3P2O5POx | SO2SO3SOx | Cl2OClO2ClO*x* | Ar |
| K2O | CaO | Sc2O3 | TiO2 | VOV2O3VO2V2O5 | CrOCr2O3CrO2CrO3 | MnOMnO2Mn3O4Mn2O7MnOx | FeOFe2O3Fe3O4 | CoOCo2O3Co3O4 | NiONi2O3Ni3O4 | Cu2OCuO | ZnOZnO2 | Ga2O3Ga2O | GeOGeO2 | As2O3As2O5 | SeO2SeO3 | Br2OBr2O5 | Kr |
| Rb2O | SrO | YOY2O3 | ZrO2 | NbO NbO2Nb2O5 | MoO2MoO3 | TcO2Tc2O7 | RuO2RuO4 | Rh2O3RhO2 | PdO | Ag2OAgO | CdO | In2OInOIn2O3 | SnOSnO2 | Sb2O3Sb2O4Sb2O5 | TeOTeO2TeO3 | I2O5I4O9IOx | XeO2XeO3XeO4 |
| Cs2O | BaO | 镧系 | HfO2 | Ta2O5 | WO2WO3 | ReO2ReO3Re2O7 | OsO2OsO4 | IrO2IrO4 | PtO2 | Au2O3 | Hg2OHgO | Tl2OTl2O3 | PbOPb2O3Pb3O4PbO2 | Bi2O3 | PoOPoO2PoO3 | At | RnO3 |
| Fr | RaO | 锕系 | Rf | Db | Sg | Bh | HsO4 | Mt | Ds | Rg | Cn | Nh | Fl | Mc | Lv | Ts | Og |
|  |  | ↓ |  |  |
| 镧系 | LaOLa2O3 | CeOCe2O3CeO2 | PrOPr2O3Pr6O11PrO2 | NdONd2O3 | Pm2O3 | SmOSm2O3 | EuOEu2O3 | Gd2O3 | Tb2O3Tb4O7TbO2 | Dy2O3 | Ho2O3 | Er2O3 | Tm2O3 | YbOYb2O3 | Lu2O3 |
| 锕系 | Ac2O3 | ThOThO2 | PaOPaO2Pa2O5 | UO2UO3U3O8UOx | NpO2Np2O5Np3O8 | PuO2 | Am2O3AmO2 | Cm2O3CmO2 | Bk2O3BkO2 | Cf2O3 | Es2O3 | Fm | Md | No | Lr |

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| 规范控制 編輯維基數據鏈接 | 
* GND: 4146385-7

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