XRD Peak Shift Research Articles

Room temperature growth of In xGa 1− xN thin films by mixed source modified activated reactive evaporation

Polycrystalline In x Ga 1− x N thin films were prepared by mixed source modified activated reactive evaporation (MARE) technique. The films were deposited at room temperature on glass substrates without any buffer layer. All the films crystallize in the hexagonal wurtzite structure. The indium concentration calculated from XRD peak shift using Vegard's law was found to be varying from 2% to 92%. The band gap varies from 1.72 eV to 3.2 eV for different indium compositions. The indium rich films have higher refractive indices as compared to the gallium rich films. The near infra-red absorption decreases with gallium incorporation into InN lattice which is mainly due to decrease in the free carrier concentration in the alloy system. This fact is further supported from Hall effect measurements. MARE turns out to be a promising technique to grow In x Ga 1− x N films over the entire composition range at room temperature.

Estimation of neutron-irradiation-induced defect in 3C–SiC from change in XRD peak shift and DFT study

Neutron-irradiation-induced defects in 3C–SiC irradiated to 2.8–4.2×1026n/m2 at 480–735°C were investigated by XRD measurement, isochronal annealing and DFT calculation. The XRD peak shift revealed different features between the specimens irradiated at 480°C and higher temperature than 585°C. The peak shifts were larger at the higher angle in the specimen irradiated at 480°C, while the specimens irradiated at higher temperature than 585°C, amounts of their peak shifts were not simply related to the diffraction angles. Crystal lattice of the specimen irradiated at 480°C was considered to expand isotropically due to the irradiation. On the other hand, that of the specimens irradiated at higher temperature than 585°C would expand anisotropically. Modification of XRD profile by the formation of various kinds of point defects and their clusters in 3C–SiC was simulated using Rietveld method based on the DFT calculation results. Formation of the CC100 dumbbell complex defect expressed well the XRD peak shifts of 3C–SiC irradiated above 585°C.

Effect of TiO 2 on phase evolution and microstructure of MgAl 2O 4 spinel in different atmospheres

The effect of TiO 2 on the formation and microstructure of magnesium aluminate spinel (MgAl 2O 4) at 1600 °C in air and reducing conditions were investigated. Under reducing conditions, stoichiometric MgAl 2O 4 spinel shifted toward alumina-rich types owing to volatilization of MgO, resulting in an increase in the porosity of fired samples. Addition of graphite to mixtures of MgO and Al 2O 3 intensified the reducing conditions and accelerated the formation of non-stoichiometric MgAl 2O 4. For TiO 2-containing samples on addition of MgAl 2O 4, magnesium aluminum titanium oxide (Mg x Al 2(1− x) Ti (1+ x) O 5, x = 0.2 or 0.3) was detected as a minor phase. Under reducing conditions, XRD peak shifts were smaller for TiO 2-containing samples than for samples without TiO 2 owing to the formation of a solid solution of TiO 2 in MgAl 2O 4 and establishment of alumina-rich spinel, which have opposite effects on increasing the lattice parameter. In bauxite-containing samples, MgAl 2O 4 spinel, corundum, magnesium orthotitanate spinel (Mg 2TiO 4) and amorphous phases were identified. Mg 2TiO 4 spinel formed a complete solid solution with MgAl 2O 4 spinel but Mg 2TiO 4 remained as a distinct phase owing to the heterogeneous microstructure of bauxite-containing samples. Also dense microstructure established in air fired TiO 2 containing samples. The results are discussed with emphasis on the application and design of alumina–magnesia–carbon refractory materials, which are used in the steel industry.

Preparation of Ti 1− zNb zN ceramics by spark plasma sintering Ti 1− zNb zO xN y nanopowders

Ti 1− z Nb z N ceramics were fabricated by sintering nanocrystalline titanium–niobium oxynitride (Ti 1− z Nb z O x N y ) powders using spark plasma sintering (SPS) technique at 1060 °C for 3 min in an N 2 atmosphere. The phase composition and microstructure were characterized by XRD, SEM, TEM and EDS. The results showed that Ti 1− z Nb z N ceramics remained the cubic structures of Ti 1− z Nb z O x N y powders. There were XRD peak shifts in the cubic phases between Ti 1− z Nb z N ceramics and corresponding Ti 1− z Nb z O x N y powders. During the sintering process, oxygen separated from Ti 1− z Nb z O x N y to form titanium–niobium oxides. Ti 1− z Nb z N (0 < z < 1) had a more compact structure than TiO x N y and NbO x N y . Ti 0.5Nb 0.5N ceramic had the biggest grain size in the series of Ti 1− z Nb z N.