Hint: Allotropes are different structural types of the same material that have very different physical and chemical properties. The same forces that influence other structures, such as strain, light, and temperature, cause the transition between allotropic types.
Complete answer: While at least 14 more allotropes have been identified, these are assumed to be mixed allotropes of boron structures stabilized by impurities, or are based on shaky evidence or have not been experimentally verified. Although the -rhombohedral phase is the most stable and the others are metastable at room temperature, the transition rate is negligible, so all five phases are stable. Although the -rhombohedral phase is the most stable and the others are metastable, at room temperature, the transition rate is negligible, allowing all five phases to remain. The most popular types of boron are amorphous powder boron and polycrystalline rhombohedral boron. Boron comes in a variety of crystalline and amorphous shapes. The crystalline forms \[\alpha - \]rhombohedral,\[\beta \] -rhombohedral, and\[\beta \] -tetragonal are well-known. Boron can also be synthesized in its \[\alpha \]-tetragonal and \[\gamma \]-orthorhombic allotropes under some conditions. There are two amorphous types known: one is a finely divided powder and the other is a glassy solid. Hence, the two allotropes of boron are \[\alpha \]-tetragonal and \[\gamma \]-orthorhombic.
Note: Remember that boron allotropes include \[\alpha \]-tetragonal and \[\gamma \]-orthorhombic. The decomposition of diborane at high temperatures, followed by purification through zone melting or the Czochralski method, produces very pure boron for use in the semiconductor industry.