γ-BaB2O4: High-Pressure High-Temperature Polymorph of Barium Borate with Edge-Sharing BO4 Tetrahedra,Inorganic Chemistry

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γ-BaB2O4: High-Pressure High-Temperature Polymorph of Barium Borate with Edge-Sharing BO4 Tetrahedra
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2022-01-18 , DOI: 10.1021/acs.inorgchem.1c03760
Tatyana B Bekker _{1,

2,

3} , Ivan V Podborodnikov _{1,

2} , Nursultan E Sagatov _{1,

2} , Anton Shatskiy _{1,

2} , Sergey Rashchenko _{1,

2} , Dinara N Sagatova _{1,

2} , Alexey Davydov _{1,

2} , Konstantin D Litasov _{4,

5}

Affiliation

The α- and β-modifications of barium metaborate are important functional materials used in optoelectronic devices. A new theoretically predicted modification of BaB₂O₄ has been synthesized under conditions of 3 GPa and 900 °C, using the DIA-type apparatus. The new high-pressure modification, γ-BaB₂O₄, crystallizes in a centrosymmetrical group of monoclinic syngony (P2₁/n (#14), a = 4.6392(4) Å, b = 10.2532(14) Å, c = 7.066(1) Å, β = 91.363(10)°, Z = 4). A distinctive feature of the γ-BaB₂O₄ structure is the presence of edge-sharing tetrahedra [B₂O₆] which form infinite double chains _∞[B₄O₄O_8/2] stretching along the a axis. The number of known structural types with the [B₂O₆] group is limited. Phase γ-BaB₂O₄ has the shortest distance between boron atoms of shared tetrahedra among all currently known compounds. The [B₂O₆] group angles are 95.5° and 105.5°. Thermodynamic stability and electronic properties of the γ-BaB₂O₄ modification were studied. The width of the band gap, calculated using the HSE06 functional, is 7.045 eV which implies transparency in the deep-UV region. Experimental and numerical methods which demonstrate a good match were used to the study the Raman spectra of γ-BaB₂O₄ and β-BaB₂O₄ modifications. In the Raman spectra of γ-BaB₂O₄, the most intense band at a frequency of 853 cm^–1 was found to correspond to the symmetric bending mode of the B–O–B–O ring in edge-sharing tetrahedra.

更新日期：2022-01-31

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