RESEARCH RESULTS – SYNTHESIS BY SPUTTERING DEPOSITION AND CRYSTAL GROWTH
Synthesis: Complex intermetallic phases in the Al-Pd-Ru and Al-Pd-Ir alloy system
Known to date binary and ternary alloy systems of aluminium with platinum metals (Ru, Rh, Pd, Os, Ir and Pt) usually contain structurally complex intermetallics, including stable ternary quasicrystals. The title ternary alloy systems, studied for the first time, are linked to either Al-Pd-Fe (Ru and Fe belong to the same column in the periodic table) or Al-Pd-Co and Al-Pd-Rh (Co, Rh and Ir belong to the same column in the periodic table) previously also studied by PGI-5.
Based on the updates of the Al-Ru and Al-Ir constitutional diagrams the Al-rich parts of the Al-Pd-Ru and Al-Pd-Ir constitutional diagrams were determined in the temperature range up to 1100 C. The study was carried out using powder XRD, DTA, SEM/EDX and TEM. Both alloy systems exhibit formation of complex intermetallic phases.
Synthesis: Magnetic memory effect in complex metallic alloy T-Al-Mn-Pd
The most prominent example of magnetically frustrated systems are spin glasses (SGs). A SG is a site-disordered spin system that is frustrated and spatially disordered in the sense that the spins are positioned randomly in the sample. These two properties lead to highly degenerate free-energy landscapes with a distribution of barriers between different metastable states, resulting in broken ergodicity. Typical SGs are dilute magnetic alloys of noble metal hosts (Cu, Ag, Au) with magnetic impurities (Fe, Mn), the so-called canonical spin glasses. In this paper we show that pronounced broken-ergodicity phenomena are present also in a class of ordered complex intermetallic Taylor phases T-Al3Mn, T-Al3(Mn,Pd) and T-Al3(Mn,Fe).
The Taylor-phase T-Al3Mn,T-Al3(Mn,Pd) and TAl3(Mn,Fe) series of complex intermetallic compounds, belong to the class of magnetically frustrated spin systems that exhibit rich out of equilibrium spin dynamics in the nonergodic phase below the spin–freezing temperature Tf . We observe a memory effect in these materials: The spin structure of the material stores information on isothermal aging steps carried out during zero-field cooling, which is detected by measuring the magnetisation of the sample.
Synthesis: Novel type of metadislocations in the complex metallic alloy Al-Pd-Fe
Among the group of complex metallic alloys (CMAs), materials which feature a few hundreds of even thousands of atoms per unit cell, the so-called " epsilon-type phases are one of the most fascinating. Several structurally related orthorhombic phases have been identified and are denoted "l (l = 6, 16, 22, 28, 34) according to the index of the strong (0 0 l) reflection. They are ternary extensions of the binary Al3Pd phase in the Al-Pd-(Mn, Fe) alloy systems. epsilon-type phases are also found in the alloy systems Al- Pd-(Rh, Re, Ru, Co, Ir) and Al-Rh-(Ru, Cu, Ni).
We report on the observation of new variants of metadislocations in the orthorhombic complex metallic alloy phase Al-Pd-Fe. At Fe contents above about 3 at.% we find a novel type of metadislocation in the -structure, which has a complementary counterpart hosted in all epsilon-type phases possessing phason lines as structural elements.
Research Area – Synthesis by Sputtering Deposition and Crystal Growth
Research Area: Synthesis by Crystal Growth
PGI-5 has long-standing experience in preparing high-quality single crystals of metals and alloys. Current research mainly concerns complex metallic alloys (CMAs), which at present represent a field of high interest in materials science. The preparation of these alloys, which is often the basis of internal projects in the areas of physical property determination, plasticity and defects, surface physics and phase diagrams, also represents an important service offered by the department, within the framework of international co-operations.
Research activities include the development of single-crystal growth and materials production techniques for a multitude of complex metallic alloys, various quasi-crystalline phases, as well as other metallic systems, and is conducted side by side with fundamental phase diagram and solidification studies.
The focus of research in the field of complex metallic alloys is on physical property determination, with in-house activity centred on the investigation of mechanical properties and structural defects. For these purposes, state-of-the-art techniques in crystal growth are applied together with mechanical testing and materials characterization. Regarding the latter, conventional imaging methods in transmission electron microscopy are complemented by in-situ, convergent beam and high-resolution transmission electron microscopy measurements
Research Area: Synthesis by Sputtering Deposition Technology
PGI-5 has significantly contributed to the development of high pressure sputtering deposition technology since 1987. Correspondingly-designed systems are used for the fabrication of epitaxial thin films and multilayers of oxide materials. Using oxygen under unusually high pressure (around 3 mbar), resputtering due to negatively charged oxygen ions is avoided. In this way, a stoichiometric material transfer from the target to the substrate, which is heated to about 1000°C, is achieved.
High quality thin films recently deposited using the above systems cover
- high-Tc superconductors (YBaCuO, ReBaCuO (Re = Nd, Gd, Ho, Eu), BiSrCaCuO, BiSrCaCuO, (Ba,K)BiO, Nd(Ce,Sr)CuO, and (Tl,Pb)CaCuO),
- insulators (PrBaCuO, SrTiO, LaAlO, BaTbO, BaZrO, CeO, NdCaAlO, MgO, YO, YSZ, and ZnO),
- ferroelectrics (BaTiO, PZT, LaTiO, as well as
- magnetic oxides and CMR-materials ((La,Ca)MnO, (Pr,Sr)MnO, SrRuO, and SrCoO).
Currently, focal points in sputtering deposition technology under high pressure conditions include the fabrication of electroceramic and high-Tc superconductor thin film multilayer structures along with the application potential of Josephson junctions and superconducting quantum interferometer devices (dc-SQUIDs) used, for example, in the development of sensors and spectrometric devices.