Preserving a large-scale reversible high-pressure phase under ambient conditions

Preserving the high pressure states and properties of large-sized materials under ambient conditions without external pressure loading devices is crucial for their practical applications. Here, we propose an approach to seal large-sized materials at high pressure within bulk diamond containers (BDCs) and preserve the high pressure states of the large-sized materials by recovering the BDC-sealed materials under ambient conditions. We have demonstrated that a reversible high-pressure BiIII phase with millimeter size could be preserved back to ambient conditions. This work opens a potential way to study the materials with relatively large structural feature sizes under the pressure of few GPa without external pressure loading devices.