Aligning nano-scale crystals in bulk materials

Abstract

Crystal orientation determines various material performances including magnetic, electrical, and mechanical properties. However, achieving the alignment of nano-grains along a specific crystallographic orientation in bulk materials remains a formidable challenge. Departing from conventional approaches using polycrystalline materials, we report a strategy to overcome this challenge by deliberately introducing strain-energy anisotropy to select oriented nucleation/growth of crystals in amorphous materials. To demonstrate its efficacy, we employed ferromagnetic materials as a proof of concept. Using our approach, a range of previously inaccessible bulk ferromagnetic nanomaterials with strong c-axis orientation have been created. The resulting bulk oriented nano-grained magnets exhibit a high energy density, 168 kJ m⁻³ for SmCo₇ and 235.2 kJ m⁻³ for PrCo₅ ferromagnets, greatly surpassing that of their state-of-the-art counterparts with 23%–62% enhancement. Our strategy is general and applicable to other material systems, including thermoelectric, piezoelectric, and ferroelectric materials, to achieve the desired oriented nano-grains for technological applications.