Researchers have designed Imma-B60, a new elemental boron allotrope produced by degassing sodium from sodium boride crystals. Featuring a porous open framework and a narrow bandgap under 0.2 eV, the material conducts electricity ten million times better than common boron while bending up to 32% without fracturing, according to a study published in Nature Chemistry.
Elemental boron typically wears several hats in modern technology, serving as a semiconductor or acting as an indispensable component in neutron-scattering research and nuclear applications due to its strong neutron-scattering ability. Yet its standard forms carry stubborn drawbacks. According to Phys, conventional elemental boron is naturally superhard, brittle under mechanical stress, and acts as a poor electrical conductor with wide bandgaps exceeding 1.5 eV. While scientists have long theorized about a plastic and highly conductive form of boron, actually manufacturing it remained confined to calculations and theories for over a decade because standard high-pressure, high-temperature synthesis methods force atoms into dense, tightly packed crystals.
Synthesizing Imma-B60 Through Zinc Interlayers and Vacuum Degassing
To overcome the challenge of building an open framework—where electron-deficient boron fiercely bonds with temporary metal guest atoms—researchers altered the standard synthesis route. Earlier attempts struggled because producing large, high-quality sodium boride crystals for degassing proved difficult. To fix this, the research team introduced zinc interlayers during the formation of sodium boride according to Phys, which enabled the growth of large crystals featuring sodium atoms sitting inside open channels of interconnected boron cages.
The team then placed those sodium boride crystals into a vacuum furnace, baking them at 900°C for two days. The vacuum pulled the sodium out through the open structural channels, leaving behind the intact framework of Imma-B60. Feng Chen and colleagues detailed this two-step scaffolding route in Nature Chemistry, describing how degassing sodium from a sodium-boron crystal yields a pure form of elemental boron entirely distinct from its traditional counterparts.
Conductivity and Plasticity Measured in Nanopillars
Unlike the dense atomic arrangements of standard boron, Imma-B60 builds its structure from 12-atom boron cages connected by 3-atom triangular boron units. This porous open framework shifts internally under mechanical stress. Compression tests performed on Imma-B60 nanopillars demonstrated that the material can achieve roughly 32% strain without fracturing
, while general testing showed it deforms by 23% without shattering. High-resolution imaging revealed that this bendiness relies on a dislocation-mediated slip mechanism where atomic planes slide smoothly past each other under stress.
Electrically, the new allotrope operates as a narrow-bandgap semiconductor. With a bandgap under 0.2 eV, Imma-B60 conducts electricity at room temperature at roughly S m-1. This performance is approximately seven orders of magnitude—or 10 million times—higher than common rhombohedral boron. The researchers believe this open-framework architecture could provide a foundation for designing mechanically resilient, functional inorganic materials that expand boron applications well beyond traditional semiconductor phases.
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