Electronic Structures and Linear Optics of A₂B₂O₅ (A = Mg, Ca, Sr) Pyroborates

Abstract

The electronic structure and linear optical properties of the pyroborate A 2 B 2 O 5 (A ) Mg, Ca, Sr) compounds are reported here. These compounds, which crystallize with four formula units in the monoclinic space group P2 1 /c, are modeled in terms of the cluster units (A 2 B 2 O 5 ) 2 . The calculated electronic structures show that the top of the valence band consists of mostly the O-2p orbitals and the bottom of the conduction band consists of cationic orbitals. The dynamic refractive indices of these pyroborates are obtained in the framework of the INDO/ SCI approximation together with the sum-over-states method. It is found that the refractive index increases with an increase of alkaline-earth cationic radius for pyroborates, and the charge-transfer for O 2anion orbitals to A 2+ cation orbitals appears to provide a significant contribution to the linear polarizability of these compounds.

Preparation, crystal structure and photoluminescence of Mn2+-doped magnesium pyroborates solid solutions, (Mg1–xMnx)2B2O5

“…Cheng et al [11] and Stewart [12] theoretically calculated the band gap width of Mg 2 B 2 O 5 to be about 5.3 eV (230 nm) for both triclinic and monoclinic phases. Recently, nanostructures such as nanowires [13] and nanorods [14] of Mg 2 B 2 O 5 have been prepared.…”

Easy synthesis of CaB2O4 via pyrolysis of calcium fructoborate

“…It crystallizes in the orthorhombic space group Pnca with Z = 4 and the structure is conformed by triangular BO 3 As mentioned above, the obtained samples presented a welldefined and characteristic X ray powder diagram which only shows the typical reflections of CaB 2 O 4 .…”

“…Crystalline inorganic borates constitute a technologically important class of oxide materials which display widespread application in high-performance devices [1][2][3] . Besides, the structural chemistry of solid borates is characterized by a considerable diversity that comes from the ability of the boron atoms to bind to three or four oxygen atoms, viz.…”

“…Besides, the structural chemistry of solid borates is characterized by a considerable diversity that comes from the ability of the boron atoms to bind to three or four oxygen atoms, viz. by forming isolated trigonal planar BO 3 or tetrahedral BO 4 groups. The condensation of these groups also generates a vast array of oligomeric or polymeric structures 4 .…”

The Synthesis and Physical Properties of Magnesium Borate Mineral of Admontite Synthesized from Sodium Borates

“…The main originality of the study is to produce magnesium borate compounds at lower temperatures and shorter reaction times, which leads to less energy consumption and time for a green chemistry approach. Another novelty of this study is the investigation and comparison of the electrical and optical characteristics of bulk and nanowires magnesium borate crystal that were investigated in the literature [16,22,23]. The bulk magnesium borate crystal has a wide optical band gap of 5.44 eV according to theoretical calculation [22].…”