Pb4Zn2B10O21: a congruently melting lead zinc borate with a novel [B10O24] anionic group and an interesting [Pb4O12]∞ chain

Abstract

A new lead zinc borate, Pb₄Zn₂B₁₀O₂₁, has been synthesized and the crystal structure was determined by single crystal X-ray diffraction. It crystallizes in the orthorhombic group Pbcn with a = 14.6062(15) Å, b = 17.4899(16) Å, c = 13.2962(15) Å, Z = 8. Interestingly, in the crystal structure, a new B–O building unit [B₁₀O₂₄] group is observed and the four different coordinated Pb atoms are connected with each other by sharing a corner, edge or face to form an interesting regular [Pb₄O₁₂]_∞ chain. The DSC analysis proves that Pb₄Zn₂B₁₀O₂₁ melts congruently. First-principles electronic structure calculation shows that the calculated band gap of Pb₄Zn₂B₁₀O₂₁ is 3.53 eV, which is in good agreement with the experimental value measured from the UV-vis-NIR absorption spectrum, and the observed absorption peak is assigned as a charge transfer from O 2p states to Pb 6p states.