New Lead Borate Pb2B6O11 and Possibility of Synthesis of Lead Analogue of Maleevite in the PbO–BaO–B2O3–SiO2 System

The PbO–BaO–B₂O₃–SiO₂ system is studied using solid-state synthesis and melt crystallization methods and attempts are made to obtain samples of the maleevite (BaB₂Si₂O₈)—lead maleevite (PbB₂Si₂O₈) series. Due to the strong tendency of Pb-containing borosilicate materials to form glass, a lead-enriched analogue of maleevite is not obtained. In the study, a new lead borate Pb₂B₆O₁₁ (sp. gr. P–1, a = 6.582(1) Å, b = 6.593(1) Å, c = 11.310(2) Å, α = 98.29(1)°, β = 90.65(1)°, γ = 119.10(2)°, V = 422.4(1) ų) and a series of solid solutions (Ba_{1 – x}Pb_x)₃B₆Si₂O₁₆ (x = 0.2, 0.4, 0.6) are synthesized and characterized for the first time. The layered compound Pb₂B₆O₁₁ has a new structural type, while the solid solution (Ba_{1 – x}Pb_x)₃B₆Si₂O₁₆ is a structural analogue of the previously known Ba₃B₆Si₂O₁₆.