Crystal structure, conductivity, vibrational, spectroscopic and thermal properties of Rb3Eu3[BO3

Abstract

The new europium borate Rb3Eu3[BO3]4 is found in the ternary system Rb2O–Eu2O3–B2O3. The Rb3Eu3[BO3]4 powder was fabricated by solid-state synthesis at 750°С for 40 h and the crystal structure was obtained using by the Rietveld method. Rb3Eu3[BO3]4 crystallizes with the monoclinic K3Er3[BO3]4-type structure in space group P21/c with unit cell parameters of a = 10.7780 (3), b = 18.0508 (5), c = 14.2213 (5) Å, β = 111.108 (1)°, V = 2581.1 (1) Å3, Z = 8. DSC and TG measurements indicate that Rb3Eu3[BO3]4 undergoes the solid state decomposition at temperature of 1014 °C. The spectral range of transparency for Rb3Eu3[BO3]4 is between 0.35 and 8 μm and the band gap of Eg ∼ 3.77 eV. The electronic structure of Rb3Eu3[BO3]4 was estimated using density functional theory. An IR analysis confirmed the presence of [BO3]3– groups in Rb3Eu3[BO3]4 crystal structure. At a temperature of 700 °C, the ionic conductivity of the title compound reaches 0.5·10−3 S/cm (Еа = 0.9 eV).