Synthesis, Structure and Properties of Compounds Derived from Kotoite-related Structures: A₂MB₂O₆ (A=Zn, Ba, Pb;...

A series of compounds with the general formula A₂MB₂O₆ (A=Zn, Ba, Pb; B=Pb, Ba, Zn, Cu) related to the kotoite structure has been prepared employing high-temperature solid state methods. The substitution of transition elements in place of Zn²⁺ ions resulted in colored compounds. The optical absorption spectra could be explained based on Tanabe-Sugano diagram and allowed d-d transitions. Dielectric studies on Ba₂ZnB₂O₆, (Ba_1.5Pb_0.5)ZnB₂O₆, PbZn₂B₂O₆, Pb_1.5Zn_1.5B₂O₆, BaZn₂B₂O₆ and Pb₂CuB₂O₆ at room temperature indicate reasonable values at low frequencies, which decrease on increasing frequencies. Magnetic study of synthesized single-phase compounds BaZnCoB₂O₆ and Pb₂CuB₂O₆ have been performed. The substitution of Eu³⁺, Tb³⁺ and Tm³⁺ in place of Ba²⁺ in Ba₂ZnB₂O₆, gives rise to the expected emission of red, green and blue colors. Suitable modifications of the different phosphors in Ba₂ZnB₂O₆, resulted in white-light emission in Ba₂ZnB₂O₆. The Pb₂CuB₂O₆ compound was found to be a good catalyst in the ipso-hydroxylation of arylboronic acids.