Linear and nonlinear optical properties of aluminum borate crystal Al₅BO₉: Experiment and calculation

Abstract

A noncentrosymmetric aluminum borate crystal, Al 5 BO 9 , was obtained via high-temperature solution method. Considering the structure diversities of Al 5 BO 9 , the single crystal structure was cautiously redetermined before the investigation. The fundamental building blocks of the structure are BO 3 triangles, AlO 4 tetrahedra, and AlO 6 octahedra. Since Al 5 BO 9 only consists of strong covalent B-O and Al-O bonds, it is worth investigating the structure-optical property relationship thoroughly, especially the linear and nonlinear optical properties. To gain further insight into the origin of the nonlinear optical response of Al 5 BO 9 , the electronic structure calculations, second harmonic generation (SHG)-weighted electron density, and dipole moment of polyhedra were analyzed in detail. All evidences deduced from calculated results indicate that the SHG contribution from the Al-O polyhedra is more pronounced than that of the BO 3 group in Al 5 BO 9 , which is anticipated to open a window for the search and design of new inorganic materials.

Al5BO9: A Wide Band Gap, Damage‐Tolerant, and Thermal Insulating Lightweight Material for High‐Temperature Applications

“…It is obvious that Al 5 BO 9 is an insulator with a direct band gap of 6.4 eV. This DFT calculated band gap is close to the experimentally determined value of 6.2 eV, but much higher than those calculated by using LDA and GGA functionals (e.g., the band gap calculated by An el al . using LDA is 4.8 eV and that by the present authors using GGA is 4.9 eV).…”

“…Low minimum thermal conductivity has been predicted and proven in many oxide ceramics like ZrP 2 O 7 [1.15 W·(m·K) −1 ], β‐AlPO 4 [1.20 W·(m·K) −1 ], β‐Yb 2 Si 2 O 7 [1.12 W·(m·K) −1 ], Yb 3 Al 5 O 12 [1.22 W·(m·K) −1 ], Yb 2 SiO 5 [0.74 W·(m·K) −1 ], Y 4 Al 2 O 9 [1.13 W·(m·K) −1 ], MSiO 4 (1.54 for ZrSiO 4 and 1.24 W·(m·K) −1 for HfSiO 4 ), Mg 2 Al 4 Si 5 O 18 (1.33 for α‐Mg 2 Al 4 Si 5 O 18 and 1.29 W·(m·K) −1 for β‐ Mg 2 Al 4 Si 5 O 18 ), and Re 2 SiO 5 (0.81–1.01) . All these materials have strong anisotropic chemical bonding and elastic properties.…”

“…For example, useful results have been obtained by Aryal et al through electronic structure investigation of mullite compounds in aluminosilicate system. For Al 5 BO 9 , the electronic structure and optical properties were investigated by An et al and a direct band gap of 4.8 eV was obtained, which is smaller than the experimental value of 6.2 eV. But the intrinsice mechanical and thermal properties were not predicted.…”

“…Recently, B‐containing mullite compounds have attracted the attention of material scientists as well as physicists and chemists due to the fact that they have lower density than the mullite compounds in aluminosilicate system and are thus more attractive as lightweight insulating and thermal protecting materials for aerospace applications . Among the B‐containing mullite ceramics, Al 5 BO 9 is intriguing because it has a low theoretical density of 2.95 g/cm 3 and is promising for applications as substrates for catalytic converters, optically translucent ceramics for high‐temperature windows, neutron absorbers in nuclear plant, thermal sealing and insulating materials in hypersonic vehicles, and reinforcements for soft metals and ceramics . A number of efforts have been devoted to fabricate Al 5 BO 9 powders, whisker, and nanowires, and to investigate the mechanical and thermal properties of Al 5 BO 9 .…”

High-pressure synthesis and crystal structure of the mixed-cation borate Ga4In4B15O33(OH)3

“…In the last decade, extensive research has been carried out in the field of group 13 element borates which yielded numerous new structures featuring interesting properties. For instance, triel borates have been reported to show luminescence when being doped with a suitable activator ion [1][2][3][4], and acentric compounds have been described as possible NLO materials [5][6][7]. Especially gallium and indium borates shifted into the research focus due to their photocatalytic properties.…”