New paradigm for glassy-like anomalies in solids from fundamental symmetries

Glasses and disordered materials are known to display anomalous features in the density of states, in the specific heat and in thermal transport. Nevertheless, in recent years, the question whether these properties are really anomalous (and peculiar of disordered systems) or rather more universal than previously thought, has emerged. New experimental and theoretical observations have questioned the origin of the boson peak (BP) and the linear in T specific heat exclusively from disorder and two-level systems (TLS). The same properties have been indeed observed in ordered or minimally disordered compounds and in incommensurate structures for which the standard explanations are not applicable. Using the formal analogy between phason modes (e.g., in quasicrystals and incommensurate lattices) and diffusions, and between amplitude modes and optical phonons, we suggest the existence of a more universal physics behind these properties. In particular, we strengthen the idea that linear in T specific heat is linked to low energy diffusive modes resulting from fundamental symmetries, and that a BP excess can be induced in crystals either by gapped optical-like modes and/or by anharmonic diffusive (Akhiezer) damping.

Characterization of LUSI Mud Volcano as Geopolymer Raw Material

The mud of mud volcano samples were collected from an eruption site named ‘LUSI’ (Lumpur “mud” –Sidoarjo), East Java, Indonesia for characterization. Analysis showed that, the major constituents of mud are SiO2 and Al2O3 which are higher than those in fly ash. The particle of mud has a flake-shaped particle and the overall particle size is dominated by particles between 2.5µm – 25.0µm. The results of XRD shows that mud of mud volcano have a characteristic of structurally disordered compounds, and a set of peaks corresponding to minor crystalline phases such as quartz, feldspars, and kaolinite. FTIR adsorption bands of the raw material of mud have the chemical bonding between bands 1-5.

THE METHOD OF ELECTRON PARAMAGNETIC RESONANCE FOR QUANTUM ELECTRONIC MATERIALS INVESTIGATION (YAG, YLuAG, YAP, YLuAP, PbGa2S4)

The results of EPR investigations of the laser crystals and scintillators are presented, in particular, Y 3 Al 5 O 12: Dy 3+, Y 3 Al 5 O 12: Er 3+, ( Y 1-x Lu x)3 Al 5 O 12: Er 3+, YAlO 3: Er 3+, Ce 3+, Nd 3+ and Tm 3+, Y (1- x ) Lu x AlO 3 : Ce 3+, PbGa 2 S 4 : Dy 3+, Nd 3+ and Ce 3+. EPR signals of Er 3+, Ce 3+, Nd 3+ and Tm 3+ ions in YAlO 3, as well as of Dy 3+, Nd 3+ and Ce 3+ in lead thiogallate single crystals are detected and analyzed for the first time. The main values of g tensors and hyperfine interaction constants for Er 3+, Tm 3+, Nd 3+ and Dy 3+ odd isotopes are determined. In compositionally disordered compounds YLuAG and YLuAP several new paramagnetic Er 3+ and Ce 3+ centers are observed in comparison with YAG and YAP . These centers appear as a result of the changes in the crystal field symmetry and magnitude due to the isomorphic substitution of Lu 3+ for Y 3+ in the yttrium sublattice. The origin of these new paramagnetic centers is established and their formation probability is calculated depending on the content of the additional lutetium impurity. Possible mechanism of the charge compensation for heterovalent substitution of Pb 2+ by RE 3+ in lead thiogallate single crystals is analyzed.