[en] The thin films of TiO₂ have been investigated extensively in the last years, since they have a broad variety of applications, which owing to their less usual chemical, electrical and optical properties. In this work are presented the obtained results to deposit TiO₂ thin films over glass substrates utilizing the Laser ablation technique. It has been deposited thin films at different substrate temperatures and different oxygen pressures, with the purpose to study the influence of these deposit parameters in the structural characteristics of the obtained films. The structural characterization was realized through Raman spectroscopy and X-ray diffraction (XRD), the superficial morphology was verified by Scanning Electron Microscopy (SEM). The results show that the obtained films were TiO₂ in rutile phase, getting this with the substrates at low temperature, its morphology shows a soft surface with some sprinkling particles and a good adherence. (Author)

[en] Positron annihilation spectroscopy has been used to get information about the small pore structure of the system xTiO₂.(1-x)SiO₂ (x=10,30 mol.%). The pore radius and volume probability distribution functions have been received from the ortho-Positronium lifetime probability distribution function, obtained by the lifetime spectra processing with CONTIN (PALS-2) program. The linearity of the S versus W-parameters has been used to check the similarity (or not) of the defect structure of the samples prepared under different experimental conditions. (author)

[en] Full text: The Materials Research Group at Curtin University has made extensive use of the Lucas Heights neutron powder diffraction facilities over the last decade. The paper will summarise the following neutron diffraction experiments all of which involved high-temperature, real-time measurements with the MRPD diffractometer: 1) Microstructure development in zirconia-dispersed aluminas (van Riessen, 1997) in which phase composition changes and residual strain development were examined as the material cooled to room temperature following sintering. 2) Calcination of gibbsite to α-alumina (Gan, 1996). A highlight of this study was the observation of co-existing tetragonal and cubic polymorphs of γ-alumina. 3) Study of the liquid-phase-sintering of an alumina-matrix ceramic composition (Latella, 1995; Latella et al, 1998). Here the influence of the post-sintering cooling rate on phase composition was examined with particular reference to wear-resistant behaviour

[en] Full text: Oxide materials form a large group of technologically and scientifically important materials, and research on these types of materials is on the forefront of scientific research. The important properties of these materials, such as the electronic, magnetic and mechanical properties, are related to the structure and chemical composition of those materials. As the structure is so important in the understanding of the properties, neutron scattering is playing a key role due to its advantages in characterising the role of the oxygen. We present here some examples of the latest oxide structures studied by neutron powder diffraction at ANSTO

[en] Full text: The necessity of integration of magnetics with silicon processing technology became essential with the advent of Micro Electromechanical Systems (MEMS). The need to control the crystalline and magnetic properties of the magnetic thin films on silicon substrates has been the primary motivation for this work. The major objective of this work is to prepare the stoichiometric and crystalline SmCo₅ thin films with good magnetic properties on single crystal silicon substrate. We have prepared the SmCo think films on single crystal (100) silicon substrates using DC magnetron sputtering. Films have been prepared in pure argon as the sputter media at two different pressures 2 x 10_-2 torr and 2 x 10₃ torr with the substrates kept at room temperature, 500 and 700 deg C separately. These films have been characterised using RBS, XRD and SEM. RBS analysis showed that the films are nearly stoichiometric (1:4.9) and have significant amounts of oxygen as impurity. But XRD studies indicated that the as deposited films (at all substrate temperatures) are yet to form the crystalline structure. Some of the films have been subjected to rapid thermal annealing at two different temperatures at 800 and 1000 deg C for 30 secs in an effort to crystallise the films. RBS analysis of these films indicated that the room temperature and post annealed films at 1000 deg C resulted in considerable interdiffusion characteristics, whereas the high temperature deposited (500 and 700 deg C) and annealed films showed relatively very stable characteristics with minimal diffusion between the film and the substrate. XRD and SEM analysis of the films is in progress. The detailed results of these investigations will be presented

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[en] Full text: Zirconolite is the key Synroc phase for the immobilisation of actinide-rich radioactive waste. The successful incorporation of actinide elements into zirconolite is critically dependent upon a knowledge of the prevailing valence state and site location for each of the elements under the selected processing atmosphere. A series of Ce- (used as a nonradioactive simulant for Pu) Pu- and Np-bearing zirconolites representing the alternative valence states (+3 or +4) and site locations (Ca or Zr site) have been prepared and sintered under a range of oxygen pressures, prior to being analysed by XRD and analytical SEM. From these techniques the valence state and site locations of the actinide elements have been inferred. X-ray absorption spectroscopy (XAS) however offers an opportunity to determine these properties directly. These results will be discussed, and preliminary conclusions drawn about the role of cerium as a nonradioactive simulant for plutonium

[en] An overview of the research and development activities in the area of high pressures carried out at the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam is presented. Experimental techniques for performing x-ray diffraction, electrical resistivity, Raman scattering and positron lifetime have been developed. In particular, the electrical resistivity measurements can be carried out at low and high temperatures. One of the novel developments has been the adaptation of the diamond anvil cell (DAC) in the Guinier geometry for carrying out high pressure x-ray diffraction experiments. Use of this geometry has resulted in a data acquisition with high signal-to-noise ratio. Although all the experiments at IGCAR are based on static pressure apparatus, namely, metal, Al₂O₃ + TiO₂ and diamond anvil cells, dynamic method using the exploding wire technique is utilised for observation of pulse of neutrons from nuclear materials under shock condition. A variation of this technique, namely, isobaric resistive pulse heating is being developed for studying the thermophysical properties. Significant progress has been made in the indigenous development of a DAC. A precision fabrication of a Mao-Bell type DAC has been carried out based on the inputs from the design considerations obtained through finite element analysis. Another noteworthy achievement is the installation of the band structure programmes based on linear methods. Typical results obtained using the high pressure techniques are highlighted to give a flavour of the research done at IGCAR. The article closes with an account of the future directions of the research and development activities at this Centre

[en] Glass-ceramic powders with a composition of Li₂O·Al₂O₃·4SiO₂ (LAS) have been synthesized by the sol-gel technique using LiOCH₃, Al(OC₂H₅)₃, Si(OC₂H₅)₄, Ti(OC₂H₅)₄, and Zr(OC₂H₅)₄ as starting materials and investigated and the phase transformation behavior during calcination. Differential thermal analysis (DTA), x-ray diffraction (XRD), and scanning electron microscopy (SEM) were utilized to determine the thermal behavior of the gels. Considering the LAS gels with TiO₂ 6.0 wt.% and various wt.% ZrO₂ content, the peak position of β-spodumene phase formation in DTA curves was shifted to a higher temperature when the ZrO₂ content was increased. The activation energy of β-spodumene crystallization was 283.8 kcal/mol for LAS gels with TiO₂ 6.0 wt.% and 2.0 wt.% ZrO₂. Unlike foregoing studies for LAS gels, during calcination of the dried LASTZ gels from 800 degree C to 1200 degree C neither β-eucryptite, nor γ-spodumene was noted to be present. The crystallized phases comprised of β-spodumenes as the major phase and rutile (TiO₂) together with zirconia (ZrO₂) are precipitated as minor phases. copyright 1996 Materials Research Society