Construction of spontaneously polarized ceramic via synergistic mechanical activation‒Biomimetic mineralization for activating air and water

Spontaneously polarized crystals with intrinsic electric dipole moment have attracted immense interest as excellent functional materials for extensive applications. It is of great significance to engineer sustainable spontaneously polarized materials with fascinating characteristics and performance for activating air and water. Herein, a novel strategy based on the synergy of mechanical activation (MA) and biomimetic mineralization (BM) was created to construct spontaneously polarized ceramic. MA induced the structural damage of clay and promoted the dissolution of ions and the release of free proteins, contributing to the formation of silicate precursor in BM process. After high temperature firing, the silicate precursor in clay was converted to form KCa3AlCa3Si4O16 (hexagonal crystal system, L6 symmetry type, and P63 space group) in the resulting spontaneously polarized ceramic. The non-centrosymmetric structure of KCa3AlCa3Si4O16 and the high intrinsic electric dipole moments contributed by K(1) polyhedrons resulted in high spontaneous polarization (0.2322 μC/cm2) and far-infrared emissivity (0.951) of spontaneously polarized ceramic. In air, spontaneously polarized ceramic can activate H2O and O2 molecules to form negative air ions owing to surface electric field. In water, spontaneously polarized ceramic can disaggregate large water clusters to form small water clusters ascribed to surface electric field and far-infrared emission; water pH can be regulated from weak acidity to approximate neutrality via the capture of electrons by H+ ions to produce releasable hydrogen gas. This work provides great promise for rational design and synthesis of spontaneously polarized materials for functional applications.