Ture Lindbäck

DC field dependent properties of Na0.5K0.5NbO3/SiO2/Si structures at millimeter-wave frequencies

Dielectric properties of laser-ablated 0.5-μm-thick c-axis epitaxial Na0.5K0.5NbO3 films on high-resistivity (7.7 Ω cm) silicon SiO2/Si substrate are studied experimentally at frequencies up to 40 ...

Reaction sequence in the formation of perovskite Pb(Zro0.48Ti0.52)O3—Pb(Nb23Ni13)O3 solid solution: Dynamic heat-treatment

Abstract The sequence of the solid state reactions in the PbOZrO 2-TiO2-Nb2O5-NiO system has been investigated. The oxide mixing route utilised in sample preparation was selected in order to determine the basic reaction path in the formation of the PZTPNN perovskite phase. It has been established that the main intermediate phases formed prior to PZTPNN are PbTiO3 and pyrochlore Pb-Nb-based phases. The sequence in the pyrochlore formation was from tetragonal Pb3Nb2O8 (500 °C) to rhombohedral Pb2Nb2O7 (600–750 °C) and finally to cubic Pb3Nb4O13 (650–850 °C). The formation of the perovskite phase proceeded from mutual solubility of PbTiO3 and pyrochlore Pb3Nb4O13 phases, accompanied by dissolving of residuals (PbZrO3 and NiO) in the perovskite solid solution formed.

Mechanical-thermal synthesis of Al2O3-Cr composite powders

Three different approaches have been investigated to synthesize alumina-chromium composites by displacement reactions between aluminium and chromia. The reactions have been performed either by pure ...

PZT phase formation monitored by high-temperature X-ray diffractometry

The crystallisation kinetics of amorphous sol-gel PZT thin films were investigated using high-temperature X-ray diffraction. Crystallisation for different isotherms was monitored as a function of time. Phase transformation data were obtained from integrated X-ray peak intensities which were calibrated based on image analysis of the surface microstructure of the samples at the end of the isothermal treatments. An activation energy of 310 kJ/mol was obtained without assuming a specific kinetic model. From the transformation data, a TTT diagram was constructed for the ranges studied.

Thermal expansion of hot isostatically pressed hydroxyapatite

A dense and transparent hydroxyapatite produced by hot isostatic pressing was investigated with respect to its stability and thermal expansion behaviour in the range 20–1150 °C. The evaluation was made by high-temperature X-ray diffraction in a reconstructed test chamber with a BN sample holder and Pt as an internal (in situ) reference. No degradation of the hydroxyapatite was detected in the range investigated. The lattice parameters, aand c, were determined as a function of temperature. The linear thermal expansion coefficient, determined by dilatometry, was 17.1 × 10–6°C–1, which agreed well with the value 17.3 × 10–6°C–1 obtained by X-ray diffraction.

A kinetic model for reaction bonding process of silicon powder compact

In order to obtain detailed information about the kinetics and the reaction nature of a complex reaction process like reaction bonding of silicon nitride, mathematical modelling of the process is n ...

Kinetic Aspects of the Formation of Lead Zirconium Titanate

Abstract The kinetics of the second calcination step in the formation of PZT solid solution (with perovskite ABO 3 lattice) has been investigated by using two different particle sizes of the B-site precursor (1.91 and 5.08 μm), the finer size being obtained by prolonged milling. In-situ analysis performed by high-temperature X-ray diffractometry in a non-isothermal mode (20–800 °C) revealed a reduction of the calcination temperature by 100 °C with a decrease in particle size of the precursor. In order to clarify the mechanism of the solid-state reaction to PZT, isothermal heat treatment of the mixtures was performed in the temperature range 540–700 °C. The activation energies for the fine and the coarse powders were estimated as 150 and 210 kJ mol −1 respectively, and the reaction was found to follow the Jander model for diffusion-controlled solid-state reaction kinetics.

A high-temperature graphite furnace for X-ray powder diffraction

A modified computer-controlled high-temperature X-ray diffractometer with good stability and an upper temperature limit of more than 2300 K is described. a critical test of the system, determining the thermal expansion of Pt, Ni and AlN, showed close agreement with dilatometric and literature data. Lattice thermal expansion data of CrB2 and TiB2 up to 2100 K were also determined.

Stresses developed in reaction-bonded ceramics

Abstract A physical model is presented that predicts the stress distribution created in a particle during its reaction with a surrounding reactant to form a uniform layer of reaction product on its surface, when the reaction involves a volume change. The results of the model are applied specifically to the case of silicon reacting with nitrogen to form Si 3 N 4 . The model predicts the generation of a high, tensile hydrostatic stress in the Si core as well as high tensile radial stress and compressive tangential stress in the nitride layer. Although the model is restricted to elastic deformation only and therefore predicts unrealistically high stresses in some cases, the results are anyway of relevance in the consideration of possible non-elastic processes such as creep and fracture and also in assessing the possible effect of stress on the reaction equilibrium. It is predicted that the nitride reaction layer would fracture during the nitridation process. A second model is also presented predicting the residual stresses arising during cooling of a partially reacted particle as a result of the difference in thermal expansion of the reactant core and the reaction product layer. In the case of the reaction of silicon to silicon nitride these thermal expansion mismatch stresses are significant but small compared to the stresses due to the chemical reaction. ©