In the highly-correlated electronic system Ca1-x PrxMnO3 having the simple perovskite structure, it has beenreported that there exists the C-type orbital-ordered (COO) state accompanyingan antiferromagnetic ordering for 0.10 ≤ x≤ 0.25. According to the previous studies concerning orbital-orderedstates in simple perovskite manganites, the COO state was understood to becharacterized by a spatial array of (3z2-r2)-type orbitalsfor 3d electrons in Mn ions. The notable feature of the COO state inCa1-x PrxMnO3 is that the state with the monoclinic-P21/msymmetry appears as a result of the structural transition from the disorderedstate with the orthorhombic-Pnma symmetry. Compared with the COO-state formationfrom the cubic-Pm $\overline 3$m state, however, the formation from the disordered-Pnma statehas not been understood yet. We have thus examined the crystallographic featuresof the formation of the COO state in Ca1-x PrxMnO3, mainly by x-ray powder diffraction and transmissionelectron microscopy. In the case of x = 0.16, forinstance, the COO state was found to appear from the disordered-Pnma statearound 90 K on cooling. The notable feature of the formation is that, in thePnma state just before the COO-state formation, characteristic diffusescattering appeared around each reflection in electron diffraction patterns,together with the splitting of the 200c reflection in x-ray powder diffractionprofiles in the pseudo-cubic notation. Based on these experimental data, it isunderstood that the formation of the COO state in Ca1-x PrxMnO3 accompanies remarkable fluctuations of the C-type orbitalordering in the disordered-Pnma state.

Praseodymium doped CaFe2As2 (122 structure) and CaFeAs2 (112 structure) are characterized by modulated Low Magnetic Field Microwave Absorption (LFMA) spectroscopy. In both (Pr,Ca)122 and (Pr,Ca)112 structures, a strong hysteretic LFMA is found, with a TcH of ∼30 K and ∼26 K, respectively. However, in (Pr,Ca)122, measurements also show an unusual Narrow Peak (NP) LFMA signal appearing at higher temperatures, above the lower TcH superconducting state until a TcNP of 49 K. We associate this NP LFMA with interfacial superconductivity, which has been found previously by highly anisotropic magnetization measurements. Furthermore, the absence of NP in (Pr,Ca)112 correlates with the absence of an interfacial phase. These results give useful information about the microwave signature of interfacial superconductivity present in the (Pr,Ca)122 system, and may form a roadmap towards a stabilized high temperature superconducting phase in pnictides.

Mo3Ru5MPd (M = Ru, Rh, Pd) as the simulated materials for the undissolved residue in the nuclear fuel reprocessing were prepared by arc melting method. The physical properties and oxidation behavior of the alloys were evaluated from viewpoint of the safety and economy in the reprocessing. The electrical resistivity, ρ, of Mo3Ru5RhPd was shown to be 0.8 μΩm at room temperature. On the other hand, the ρ values of samples without Rh were marked at 0.4 μΩm. The thermal properties of the each sample had the different thermal transfer characteristics. In particular, although the thermal conductivities of Mo3Ru5RhPd and Mo3Ru5Pd2 samples show almost the same value, the lattice thermal conductivities of both samples showed different values. Oxidation behavior was analyzed using the thermogravity(TG) and differential thermal analyses(DTA). The TG curve of each sample by oxidation showed different results. These results indicate that the simulated materials of the alloys without Rh: Mo-Ru-Pd were not appropriate to simulate the thermophysical characteristics of the typical simulated materials with undissolved residue Mo-Ru-Rh-Pd alloys. Therefore, in the spent nuclear fuel reprocessing, the mock test of reprocessing without to use Rh is difficult to carry out.

This study reports the synthesis of monosized Pr nanoparticles with a controllable size ranging from 5 to 20 nm. Pr agglomerates generated by a spark generator first size-selected by a differential mobility analyzer and subsequently sintered in-flight at different temperatures result in spherical and monocrystalline Pr nanoparticles. The dependence of size and size distribution of Pr nanoparticles has been studied as a function of deposition parameters related to spark generator, differential mobility analyzer, and sintering. Transmission electron microscopy, energy-dispersive x-ray analysis, glancing angle x-ray diffraction, and x-ray photoelectron spectroscopy studies confirm that initial Pr agglomerates and the resulting nanoparticles are metallic with d-hexagonal structure and remain stable in air during post-deposition exposure. Incomplete or partially sintered nanoparticles were found to be oxidized, resulting in the formation of amorphous oxide phase due to enhanced oxidation at grain boundaries.

High-quality SrAl12O19:Pr3+ nanodisks and nanoplates were fabricated via a new processing technique based on a modified polymer steric entrapment method. Serious agglomeration and large particle size distribution of final products, which usually occurred in the conventional method, were eliminated completely. The effects of new synthetic processes on the morphology, crystallization, and yield of products and the relevant mechanisms were discussed. As far as we know, SrAl12O19:Pr3+ nanodisks with mean diameter ∼60 nm and thickness between 5 and 10 nm were successfully synthesized for the first time by this low-cost technique. The new synthetic method may provide a general route to synthesize other refractory mixed-oxide nanocrystals. Photon cascade emission involving transitions 1S0–1I6 followed by 3P0–3H4 in SrAl12O19:1% Pr3+ nanodisks was investigated. Size-effect-induced blue shift of the 4f5d states of Pr3+ was observed in SrAl12O19:1% Pr3+ nanodisks, in which the quantum efficiency was preserved, as in the bulk counterparts.

We investigate the dielectric properties of Praseodymium based oxides and silicates by preparing MIS structures consisting of a metal layer (M), PrOX (praseodymium oxide) as a high-k insulating layer (I), and silicon (Si) or silicon carbide (SiC) as semiconductor substrates (S).

The use of a buffer layer between PrOX and SiC is necessary as we found destructive interactions like silicate and graphite formation between these materials. Based on a higher permittivity value than SiO2 and a good lattice matching in conjunction with nearly the same thermal expansion coefficient to SiC, we focus on aluminum oxynitride (AlON) as a suitable buffer layer for this high-k/wide-bandgapsystem. We report on results achieved by Synchrotron Radiation Photoemission Spectroscopy (SRPES) and by electrical measurements.

In our spectroscopic investigations we found a stable AlON/3C-SiC interface as well as no elemental carbon and silicate contributions in the core levels after thin PrOX deposition and annealing up to 900°C.

In electrical characterizations of PrOX/AlON stacks on silicon we already found a strong improvement in the leakage current down to values of 10-7 A/cm2 at an CET of 4nm. We observed an interface state density in the range of 5x1011-1x1012/eVcm2 and 1-5x1012/eVcm2 on Si and SiC, respectively.

We combine high-k dielectrics with wide band gap semiconductors for new possibilities for high frequency and high power applications. We investigate the dielectric properties of Praseodymium based oxides and silicates by preparing MIS structures consisting of metal layer (M), PrOx (praseodymium oxide) as a high-k insulating layer (I), and silicon (Si) or silicon carbide (SiC) as semiconductor substrates (S). Our approach consists both, electrical measurements and spectroscopic characterization to analyze properties of the various interfaces within the stacks.

For the electrical measurements we produce PrOx layers in the thickness range of 10nm to 240nm. We use capacitance-voltage analysis and determine permittivity values of 8 to 20 depending on physical thickness resulting in an equivalent oxide thickness (EOT) down to 5nm. These data are consistent with the formation of a Pr-silicate between Si and PrOx.

In order to prevent interface reactions and to improve the band alignment an interfacial layer is introduced into the stack between the semiconductor and the high-k material. We find aluminum oxynitride (AlON) as a suitable layer which reduces the interface state density to a mean value of 5E11cm2/Vs and the leakage current (1V above flat band) below 1E-5A/cm2.

Pr doped YBa2Cu3O7-d targets with composition Y1-xPrxBa2Cu3O7-d where × = 0.0001, 0.001, 0.01, and 0.1 were prepared from oxide powders and were used to deposit thin films by pulsed laser deposition using conditions previously optimized for pure YBa2Cu3O7-d. The Pr dopant was found to be dispersed throughout the film by secondary ion mass spectrometry and found to have an increased density of nanoparticles on the surface. The pinning force of the doped samples was found to decrease with increasing concentration of Pr; however, at 0.01% concentration the doped film displayed a significant enhancement over pure YBa2Cu3O7-d for nearly the full range of 0 – 9 T.