THE COORDINATION COMPOUNDS Gd (III) AND Dy(III) WITH SOME β-DIKETONES

New complexes of Dy (III) and Gd (III) with b-diketones containing unsaturated and aryl substituents were synthesized. Metal polymers based on synthesized complexes were obtained by the method of radical polymerization. The composition and structure of synthesized complexes and metal polymers are established. It is shown that during polymerization the coordination environment of the central ion remains unchanged. The spectral-luminescent cha­racteristics of the synthesized compounds were studied. The presence of water molecules in the immediate coordination environment causes a low intensity of emission of monomeric dysprosium complexes. In the luminescence spectra of metal polymers, there are bands magnetic dipole transition (4F9 → 6H15/2) and electric dipole transition (4F9 → 6H13/2). The close energies of the triplet level of the ligand and the resonant level of the dysprosium ion cause low emission characteristics of the synthesized dysprosium complexes.

Anomalous enhancement of thermoelectric power factor by thermal management with resonant level effect

Thermoelectric power factor enhancement through thermal management with resonant level effect is experimentally demonstrated in SiGeAu composite system.

Study of CaF2- Doped PbTe Thin Films Grown by Molecular Beam Epitaxy

We present here a study on the electrical and structural properties of p-type PbTe films doped with CaF2. The layers were grown by molecular beam epitaxy on freshly cleaved (111) BaF2 substrates. The doping level was monitored by the CaF2 solid source cell temperature (TCaF2), which varied from 500 to 1150 °C. The films with low doping level, TCaF2 ≤ 1010 °C, exhibited flat surfaces with crystalline quality close to the undoped PbTe sample. In contrast, samples with high levels of doping (TCaF2 > 1010 °C) presented CaF2 agglomerates on the surface and a worse crystal quality. The hole density at 77 K versus TCaF2 oscillated between 1.3 × 1017 and 3.6 × 1017 cm-3 and did not exhibit a systematic behavior as the fluoride supply is raised. The results indicate that CaF2 is not an effective p-type dopant for PbTe, due to the abscence of a resonant level close to the valence band or to compensation of extrinsic dopant levels.