First‐Principles Insight into the Composition‐Dependent Structure and Properties of γ‐Alon

Abstract

Spinel type Aluminum oxynitride (γ‐alon) solid solution exists in the Al2O3‐rich region of AlN–Al2O3 systems. The first‐principles calculations facilitate our investigations on composition‐dependence of structure and properties in γ‐alon without the limit of experimental solubility. The constant anion crystal structure of γ‐alon was described as the solid solution of spinel phase γ‐Al2O3 and the ideal Al3O3N with formula of Al(8+x)/3O4−xNx (0 ≤ x ≤ 1). The unit cell expands with increasing Al3O3N composition. The lattice parameter increases nonlinearly with the composition of Al3O3N, which deviates from Vegard's law. As x increases, the anions dilate from the AlIV along (1 1 1) direction, and two new narrow peaks (approximate –12.7 and –0.3 eV) become stronger and the conduction band presents a downward shift to low energy in the TDOS. The absorption edge in the UV region of ε2(ω) present slight red‐shift of 0.5 eV as x increases. Because the compressibility was improved by expansion of coordination polyhedron, the elastic properties were just slightly enhanced as the nitrogen concentration increases. It is suggested that the notable enhancement of mechanical properties in γ‐alon may be difficult to yield by varying the content of substituted nitrogen atoms. The calculated results provide the basis for understanding the crystal structure and intrinsic properties of γ‐alon with different compositions.

Insight the Luminescence Properties of AlON: Eu, Mg Phosphor under VUV Excitation

“…It is investigated that γ-AlON is compositionally stable when z = 5, forming Al 23 O 27 N 5 due to the low concentration of Al vacancy. By comparing the system energy of two structures with different Al vacancy site (Table 1), the model with an Al vacancy in the octahedral sites have the lowest total energy and is therefore more acceptable, which agrees with the previous calculation results based on density functional theory (DFT) [19,20]. …”

High-Pressure Synthesis of Novel Boron Oxynitride B6N4O3 with Sphalerite Type Structure

“…These are structural vacancies, such as known e.g. in the spinel-type aluminium oxynitrides (γ-ALON)46,47 , not to be misinterpreted as point defects.The occupancies were fixed during structure refinement, but isotropic displacement factors of all atoms were allowed to refine freely and converged to reasonable values (cf. SI).…”

Photocatalytic properties of aluminum oxynitride (AlON)

“…These free carriers could be trapped at suitable lattice sites (defect centers) and lead to electron-hole separation, which further react with inorganic pollutant and mineralize them to non-toxic compounds. Especially, structure and properties of AlON are composition-dependant [15]. Therefore, it is expected that photocatalytic activity of AlON could be further improved by composition-controlling, by preparing nano-structure or by hybridizing with other semiconductors.…”