Syntheses,Structures And Characterizations Of Novel Metal Borate Sulfates

From the structural point of view,BOn(n = 3 or 4)groups usually can be bridged by oxygen atoms to form various types of polymeric anions which lead to many kinds of one-dimensional or multi-dimensional B-O anionic structures.Such a rich and diverse structure types determine the promising applications of borates in inorganic functional materials fields,especially in photoelectric field.In the thesis,brief review of the literatures is made from the perspectives of simple borates,complex borates and mixed anion borates to reveal the structural and functional diversity of borates.Considering the present research situations,we will introduce SO4 as building units into metal borate system,from the adjustments of B-O connection modes via SO4 tetrahedra,we successfully synthesized a series of novel borate sulfates,which enriches the structural chemistry of borates.Based on the above assumptions,we obtained a series of novel borate sulfates by hydrothermal method and high temperature solid state method.The results are as the following:(1)Sixteen rare earth borate sulfates were obtained by hydrothermal method,they crystallize in three kinds of space groups,namely,Ln(SO4)[B(OH)4](H2O)2(Ln=Pr 1,Nd 2,Sm 3,Eu 4,Gd 5,P21/m);Ln(SO4)[B(OH)4](H20)·H20(Ln=Y 6,Tb 7,Dy 8,Ho 9,Er 10,Tm 11,Yb 12,Lu 13,P-1);Ln(SO4)[B(OH)4](H20)(Ln=La 14,Sm 15,Eu 16,P-1).The three structure types show different two dimensional layers.In the structures of compounds 1-5,LnO9 polyhedra connect with BO4 and SO4 groups by sharing oxygen atoms along a and c axis to form a two dimensional Ln(SO4)[B(OH)4](H2O)2 layer parallel to the ac plane;In the structures of compounds 6-13,LnO8 polyhedra connect with SO4 tetrahedra to form a trapezoid chain along b axis,such chains are bridged by BO4 units along a axis to form a two dimensional Ln(SO4)[B(OH)4](H2O)layer parallel to the ab plane.In addition,there exist a crystallized water between layers;In the structures of compounds 14-16,two LnO9 polyhedra form Ln2O16 dimer by edge-sharing oxygen atoms,then connect with BO4 and SO4 groups along a and b axis to form a two dimensional Ln(SO4)[B(OH)4](H2O)layer parallel to the ab plane.Furthermore,we also take some relevant tests for compounds 3,4,15 and 16.Compounds 3 and 4 can be stable to about 150 ℃,but compounds 15 and 16 can be stable to about 200 ℃.Luminescent studies indicate the characteristic emission bands of lanthanides for compounds 3,4,15 and 16.Magnetic measurements suggest that there exist weak antiferromagnetic interactions between magnetic centers in compounds 3,4,15 and 16.(2)A new borate sulfate containing lead was obtained by high temperature solid state reaction.Pb4(BO3)2SO4(compound 17)crystallizes in space group P21/c,PbOn polyhedra condense into a 3D Pb-O framework with one-dimensional(1D)tunnels running along the a axis,and the isolated BO3 and SO4 units are grafted in these tunnels.Thermal behavior test shows that Pb4(BO3)2SO4 is congruent melting compound,and the melting point is 688 ℃.UV-Vis-NIR diffuse reflection spectra indicates that the band gap is 4.03 eV.