The determination of microstructural details for powder materials is vital for facilitating their selective laser melting (SLM) process. Four widely used steels (316L, H13, P20 and 18Ni300) have been investigated to detail their powders’ microstructures as well as laser absorptivity to understand their SLM processing from raw material perspective. Phase components of these four steel powders were characterized by X-ray diffraction (XRD), synchrotron radiation X-ray diffraction (SR-XRD) and scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were utilized to reveal the surface structure of these four steel powders. It is found that phase components of H13, P20 and 18Ni300 are mainly composed of martensite and a small amount of austenite due to the high cooling rate during gas atomization processing, while 316L is characterized by austenite. XPS results show that the four steel powders all possess a layered surface structure, consisting of a thin iron oxide layer at the outmost surface and metal matrix at the inner surface. It is found that the presence of such oxide layer can improve the absorptivity of steel powders and is beneficial for their SLM process.

Recently, tricritical ferroelectrics have been drawn tremendous attention, owing to their ultrahigh dielectric permittivities of up to ε_r > 5 × 10⁴, and their consideration for prototype materials in the development of high-performance energy storage devices. Nevertheless, such a materials system suffers from the disadvantage of low breakdown strength, which makes its energy density far from the satisfactory level for practical application. In this paper, a material-modification approach has been reported, for improving the dielectric strength for tricritical ferroelectric materials Ba(Ti_1−xSn_x)O₃ (BTS) through doping with Bi_1.5ZnNb_1.5O₇ (BZN) additives. The results suggest that the electric strength has been largely improved in the modified tricritical ferroelectric material (BTS_x-yBZN), and the associated energy density reaches U_e = 1.15 J/cm³. Further microstructure investigation indicates that the modified tricritical ferroelectric material exhibits homogenous fine grains with perovskite structure in crystal symmetry, and the BZN may help to form a special structure that could enhance the breakdown strength. The findings may advance the material design and development of high-energy storage materials.