Syntheses, Crystal Structures And Properties Of Novel Barium-containing Borates

In this paper, three novel barium-containing borates have been prepared by hightemperature solution reaction,including Ba8[(Al6IV)(Al2IV)(Al2V)B12IIIO41]∞, Ba4Na2-Zn4(B3O6)2(B12O24) and Ba4K2Zn5(B3O6)3(B9O19). In addition, X-ray data collectionsof all compounds were carried out on an automated Rigaku AFC7R four-circlediffractometer.The crystal structures were solved by direct methods and refined inSHELX-97system, and electronic structure and optical properties of these compoundswere investigated.Ba8[(Al6IV)(Al2IV)(Al2V)B12IIIO41]∞crystallizes in the triclinic space group P1with a=9.2437(11), b=9.8100(12), c=11.0830(14), α=76.130(10)°, β=73.550(9)°, γ=77.990(10)°, Z=1. The crystal structure contains H-shaped Al6O1920-groups built up from six corner-sharing AlO4tetrahedra.The Al6O1920-groups, AlO4tetrahedra, AlO5trigonal bipyramids, and BO3triangles are linked to form atwo-dimensional [(Al6IV)(Al2IV)(Al2V)B12IIIO41]16-layer by sharing O vertices. Thelayers are stacked along the c-axis, with the interlayer void spaces and intralayer openchannels occupied by Ba2+cations to balance charge. The IR spectrum furtherconfirmed the presence of BO3groups. UV-vis diffuse reflectance spectrum showed aband gap of about3.10eV. Solid-state fluorescence spectrum exhibited a broademission band at around430nm.Band structure calculations indicated that it is a directband material with the calculated band gap (3.25eV) close to the observed one.Ba4Na2Zn4(B3O6)2(B12O24) crystallizes in the triclinic space group P1with a=7.0288(14), b=7.0687(14), c=17.501(4), α=91.92(3)°, β=96.46(3)°, γ=119.72(3)°, Z=1. The crystal structure exhibits complicated porous anionic layerscomposed of ZnO4tetrahedra,[B3O6]3-rings with notation of3[3△], and [B12O24]12-groups built up from four BO4tetrahedra and eight BO3triangles with notation of2×{2×(3[2△+1T])}. The anionic layers stack along c-axis, with the intralayer openchannels and interlayer void spaces occupied by Na+or Ba2+cations to balance charge.The IR spectrum further confirmed the presence of both BO3and BO4groups. UV-visdiffuse reflectance spectrum revealed a band gap of about3.13eV. Solid-statefluorescence spectrum exhibited a broad emission band at around540nm. Bandstructure calculations indicated that it is anindirect band material with the calculatedband gap of about4.278eV.Ba4K2Zn5(B3O6)3(B9O19) crystallizes in the monoclinic space group P21/C (No.14) with cell parameters of a=7.1620(14), b=38.772(8), c=12.360(3), β=90.26(3)°, V=3432.2(12)3, Z=4. It has a new structure type that features two-dimensional2[Zn5(B3O6)3(B9O19)]10-anionic layers composed of ZnO4tetrahedra,[B3O6]3-rings with notation of3[3△], and [B9O19]11-groups with notation of3[2△ +1T]+3△+3[2△+1T]. The zinc borate anionic layers stack along b-axis, with theintralayer open channels and interlayer void spaces filled by Ba2+, K+, or Ba2+/K+cations to compensate the negative charges of the layers.Infrared spectrumwasmeasured, which confirms the presence of both BO3and BO4groups. The opticalproperties were investigated in terms of diffuse reflectance and fluorescent spectra,which reveal an optical band gap of3.18eV as well as a broad emission band ataround515.8nm upon laser excitation at325nm.