Structure of lithium heptaborate, Li3B7O12

THERMOLUMINESCENCE AND KINETIC PARAMETERS OF MICRO-NANO MATRIX OF LITHIUM TRIBORATE AND ZINC OXIDE NANOPARTICLE

This study presents the first report on the kinetic parameters of micro-nano interaction of lithium triborate microparticles doped with zinc oxide nanoparticles (LBZ) in 0.1 to 0.4% dopant concentrations. The parent-dopant mix was synthesized using high-temperature solid-state method. The materials were subjected to X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and differential thermal analysis (DTA) to ascertain their structural, physical properties as well as gamma irradiation and thermoluminescence (TL) analysis for their dosimetric properties. XRD and DTA confirmed the formation of polycrystalline lithium triborate compounds, while SEM and EDS showed the presence of the dopant. TL analysis presented a simple glow curve structure with the main temperature peak for different dopant concentrations varying from 243 to 327°C. The activation energy (E) and frequency factor (s) were calculated for each peak shape parameter τ (low temperature half width), δ (high temperature half-width) and ω (total half width) using Chen's peak shape (PS) method and the order of kinetics was deduced from the symmetry factor (μg) and gamma dose-response curves. The activation energy and frequency factor with respect to the peak shape parameters Eτ, Eδ, Eω and sτ, sδ, sω across the dopant concentrations were in the range of 1.14 to 2.2 eV and 3.92 × 1010 to 7.71 × 1022 s-1, respectively. Comparing the methods for the determination of the order of kinetics, LBZ 0.2% agrees with the conditions of first-order kinetics, while second-order kinetics is assigned to LBZ 0.1, 0.3 and 0.4%. The results present simple glow curve structure which relates to stability, high-temperature peaks and E values which correspond to deep trap states.

The ionic conductivity in lithium-boron oxide materials and its relation to structural, electronic and defect properties: insights from theory

We review recent theoretical studies on ion diffusion in (Li(2)O)(x)(B(2)O(3))(1-x) compounds and at the interfaces of Li(2)O :B(2)O(3) nanocomposite. The investigations were performed theoretically using DFT and HF/DFT hybrid methods with VASP and CRYSTAL codes. For the pure compound B(2)O(3), it was theoretically confirmed that the low-pressure phase B(2)O(3)-I has space group P3(1)21. For the first time, the structure, stability and electronic properties of various low-index surfaces of trigonal B(2)O(3)-I were investigated at the same theoretical level. The (101) surface is the most stable among the considered surfaces. Ionic conductivity was investigated systematically in Li(2)O, LiBO(2), and Li(2)B(4)O(7) solids and in Li(2)O:B(2)O(3) nanocomposites by calculating the activation energy (E(A)) for cation diffusion. The Li(+) ion migrates in an almost straight line in Li(2)O bulk whereas it moves in a zig-zag pathway along a direction parallel to the surface plane in Li(2)O surfaces. For LiBO(2), the migration along the c direction (E(A) = 0.55 eV) is slightly less preferable than that in the xy plane (E(A) = 0.43-0.54 eV). In Li(2)B(4)O(7), the Li(+) ion migrates through the large triangular faces of the two nearest oxygen five-vertex polyhedra facing each other where E(A) is in the range of 0.27-0.37 eV. A two-dimensional model system of the Li(2)O :B(2)O(3) interface region was created by the combination of supercells of the Li(2)O (111) surface and the B(2)O(3) (001) surface. It was found that the interface region of the Li(2)O:B(2)O(3) nanocomposite is more defective than Li(2)O bulk, which facilitates the conductivity in this region. In addition, the activation energy (E(A )) for local hopping processes is smaller in the Li(2)O :B(2)O(3) nanocomposite compared to the Li(2)O bulk. This confirms that the Li(2)O:B(2)O(3) nanocomposite shows enhanced conductivity along the phase boundary compared to that in the nanocrystalline Li(2)O.