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|Section2= |Section3= |Section7= }} Yttrium boride refers to a crystalline material composed of different proportions of yttrium and boron, such as YB2, YB4, YB6, YB12, YB25, YB50 and YB66. They are all gray-colored, hard solids having high melting temperatures. The most common form is the yttrium hexaboride YB6. It exhibits superconductivity at relatively high temperature of 8.4 K and, similar to LaB6, is an electron cathode. Another remarkable yttrium boride is YB66. It has a large lattice constant (2.344 nm), high thermal and mechanical stability, and therefore is used as a diffraction grating for low-energy synchrotron radiation (1–2 keV). ==YB2 (yttrium diboride)== Yttrium diboride has the same hexagonal crystal structure as aluminium diboride and magnesium diboride – an important superconducting material. Its Pearson symbol is ''hP3'', space group P6/mmm (No 191), ''a'' = 0.3289 nm, ''c'' = 0.3843 nm and the calculated density is 5.1 g/cm3. In this structure, the boron atoms form graphite like sheets with yttrium atoms between them. YB2 crystals are unstable to moderate heating in air – they start oxidizing at 400 °C and completely oxidize at 800 °C. YB2 melts at ~2220 °C. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Yttrium borides」の詳細全文を読む スポンサード リンク
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