BaPbO_3的电子结构与光子吸收性能

Electronic Structure and X Photon Absorption Ability of BaPbO_3

采用固体无机化学反应制备了BaPbO3微粉,确定了BaPbO3微粉的结构和低温、低Pb/Ba摩尔比合成BaPbO3的工艺。研究了该微粉对75kV的X射线的吸收性能,结果表明:含BaPbO3材料60%(wt)、厚0.64mm的吸收材料,其对X射线的吸收率为86.82%,铅当量为1.3845;而含等量的未反应的PbO和BaCO3的0.68mm的吸收材料,吸收率仅为44.43%,铅当量为0.3748。结合光子与核外电子相互作用的过程,提出了吸收原子的核外电子云的“交盖”及核外价电子在多个价轨道方向上的伸展是BaPbO3材料具有优秀的吸收性能的主要原因的推断。进一步,以推广休克尔半经验分子轨道法半定量研究了BaPbO3材料的铅-氧八面体的电子结构,证明了铅离子与相连的氧离子电子云发生交盖,且核外价电子在多个价轨道方向上均有伸展,初步分析了BaPbO3材料的电子结构与光子吸收性能之间的关系。

BaPbO3 powder was fabricated with solid inorganic reaction at low temperature of 800℃and low Pb/Ba mole ratio of 1∶1. Cubic perovskite structure of BaPbO3 was determined with XRD (X ray Diffraction), which possessed 0.427～0.428nm of lattice parameter. The X photon absorption ability of BaPbO3 powder was investigated at 75kV. A kind of composite absorption material, which consists ofBaPbO3 with different mass contents and a kind of adhesion polymer, was prepared. The absorption rate and the Lead Equivalence of one kind of absorbing materials which contains 60%(wt) of BaPbO3 powder and with a thickness of 0.64mm, is 86.82%and 1.3845 respectively. But for another absorbing material with a thickness of 0.68mm, which consists of equivalence un reacted source materials PbOand BaCO3,the rate of absorption and the Lead Equivalence is only 44.43%and 0.3748 respectively. The difference might result from the overlap of extra nuclear electron cloud and the extend of extra nuclear valence electron in multi valence orbitals of absorption atom in BaPbO3 material. The molecular orbitaland the overlap population of the octahedron configuration center occupied by Pb atom were studied by EHMO (Extended Hukel Molecular Orbital). It is the contribution of electron cloud expansion that makes up for the decline of absorptionability as material density decreasing. The relationship between X photon absorption ability and the electrical structure of BaPbO3 material was primary theoretically analyzed.