Decomposition of supersaturated solid solutions in Al–Cu–Mg–Si alloys

The Al–Cu–Mg–Si alloying system is a base for a diverse group of commercial alloys which acquire their properties after quenching and aging. Therefore, the knowledge of the phase composition of hardening precipitates and the conditions under which they are formed is very important. ast reference data were analyzed along with experimental results and calculations of phase equilibria. Different alloys were compared based on the composition of the supersaturated solid solution. It is shown that the phase composition of aging products in alloys with Mg : Si > 1 agrees well with the equilibrium phase composition at a temperature of annealing. However, the sequence of precipitation in the alloys with Mg : Si < 1 is more complicated. The hardening in these alloys occurs with precipitation of the and phases and their precursors. The former phase may contain copper and later transforms either to and (Mg₂Si) or to Q phase depending on the amount of copper and annealing temperature.     

Synthesis and microstructure characterization of tetragonal Zr1–xTixO2 (x = 0–1) solid solutions

Oxide powders of Zr_1–xTi_xO₂ (x = 0–1) solid solutions with micron-sized particles were synthesized via a solution combustion method. The synthesis process and Zr/Ti molar ratio were optimized to produce powders with the tetragonal crystal structure. X-ray diffraction, Raman spectroscopy and transmission electron spectroscopy results confirm that a full crystallization microstructure with the single tetragonal phase is obtained after calcination at 600 °C while maintaining the crystallite size <30 nm. Zr/Ti oxide mixtures with Zr ≥ 67 mol% exhibit a tetragonal crystal structure and the embedding Ti in ZrO₂ improves the structure stability. The nitrogen sorption results indicate that the powders possess mesoporous morphology with medium specific surface areas (∼10–50 m²/g). Chemical stability tests show that these powders are relatively stable with negligible removal of titanium and zirconium after elution by 0.5 mol/L HCl. Density functional theory was used to calculate the most stable structure with low energy for the selected composition.     

Synthesis and IR-excited luminescence of (Y1 − x Tm x )2O2S solid solutions

We have studied the key features of the luminescence spectra and kinetics of (Y_{1 ? x} Tm _x )₂O₂S solid solutions in the range 400–2000 nm under laser excitation at 790 and 810 nm. The results have been used to develop a series of IR phosphors “invisible” under laser excitation in the range 790–810 nm and possessing tunable and reproducible relative intensities of three groups of IR luminescence bands in the ranges 770–840, 1360–1520, and 1650–1980 nm, respectively.     

Magnetic clusters in Cu1 ? x In1 ? x Fe2x Se2 solid solutions

We have synthesized Cu_{1 ? x} In_{1 ? x} Fe_2x Se₂ solid solutions (CuInSe₂-FeSe join). The ??-FeSe end-member of the solid-solution system is an antiferromagnet and a superconductor with a superconducting transition temperature of 8 K. The magnetic properties of the solid solutions were studied at temperatures from 5 to 300 K in magnetic fields H = 3.98 and 3184 kA/m. By fitting experimental ??(H) magnetization data with Langevin and Curie equations, we determined the magnetic moment, size, and concentration of the clusters and the concentration of noninteracting Fe²⁺ ions. The magnetic moment of the Fe²⁺ ions in the clusters is ??0.8??_B at 2x = 0.06 and 0.08, with a tendency to decrease with increasing iron content. This points to antiferromagnetic exchange interaction, which becomes stronger with increasing cluster size. The number of clusters in the materials increases with iron content up to a critical level 2x _c < 2x = 0.06. In the range 2x = 0.06 to 0.10, the cluster size increases until a limiting composition determined by the boundary of the solid-solution range is reached.     

Preparation and phase transition of Gd4(Al1 − xGax)2O9 solid solutions

The solid-solution compounds of Gd₄(Al_{1 – x} Ga _x )₂O₉ (x = 0.0–1.0) were prepared at 1600°C for 5 h in air. The unit cell volume of the compounds increased from 0.853 to 0.878 nm³ with x. Phase transitions having a temperature hysteresis were observed from 1100° to 1400°C by calorimetry and dilatometry. The transition temperature increased with x. The volume of the high-temperature phase was 0.5% smaller than that of the low-temperature phase at the transition temperature. The volume changes were independent of x. The hysteresis width observed by the dilatometry was about 300°C for the Gd₄Al₂O₉ ceramics (grain size: about 1 m) and decreased to 50°C for the Gd₄(Al_0.2Ga_0.8)₂O₉ ceramics (grain size: over 10 m). Gd₄Ga₂O₉ was unstable at low temperature and decomposed to Gd₃GaO₆ and Gd₃Ga₅O₁₂ during the thermal analyses.     

Synthesis and properties of TlIn1 − x Gd x Se2 solid solutions

This paper describes the synthesis and crystal growth of TlIn_{1 − x} Gd _x Se₂ solid solutions and presents the T-x phase diagram of the TlInSe₂-TlGdSe₂ system. Partial gadolinium substitution for indium in TlInSe₂ increases the microhardness and unit-cell parameters of the material and reduces its band gap. According to X-ray diffraction data for TlInSe₂-TlGdSe₂ crystals, the TlIn_{1 − x} Gd _x Se₂ (0 < x ≤ 0.1) solid solutions crystallize in tetragonal symmetry and are isostructural with TlInSe₂.     

Phase Relations in the NiFe2O4–NiCr2O4–CuCr2O4System

The phase relations in the NiFe₂O₄–NiCr₂O₄–CuCr₂O₄system were investigated experimentally and theoretically. X-ray diffraction data were used to construct the phase diagram of the system and elucidate the structural mechanisms of the transitions from the cubic spinel structure to the tetragonal (I42d, c/a< 1 and I4₁/amd, c/a> 1) and orthorhombic (Fdd2) structures.     

Nanocrystalline CuFe solid solutions prepared by mechanical alloying

Nanocrystalline Cu_xFe(100_−x) solid solutions have been prepared by mechanical alloying. The average grain size of the powders (10–20 nm) depends on the composition of the material. The detailed process of nanocrystal formation was characterized by high resolution electron microscopy and many fine structure changes were revealed. The enhancement of solid solubility is explained according to the structural features of nanocrystals.     

Phase equilibria and decomposition of solid solutions in the YbTe–SnTe–PbTe system

Phase equilibria in the YbTe–SnTe–PbTe system have been studied using differential thermal analysis, X-ray diffraction, scanning electron microscopy, and emf measurements on YbTe concentration cells. We have mapped out a number of vertical sections, the 400-K isothermal section of the YbTe–SnTe–PbTe phase diagram, and projections of its liquidus and solidus surfaces. The results demonstrate that the system is characterized by the formation of a continuous series of high-temperature solid solutions with a cubic structure (NaCl type), which undergo decomposition below ~1050 K. At room temperature, the YbTe solubility in the Sn_1–x Pb _x Te solid solution system is ~33–35 mol %, whereas the extent of the YbTe-based solid solution series does not exceed 3 mol %.     

Conduction mechanism and dielectric properties of BiFeO3–BaTiO3 solid solutions

The first measurements are reported for the frequency-dependent conductivity of (1?x)BiFeO₃–xBaTiO₃ (x = 0.10, 0.15 and 0.30) solid solutions in the frequency range of 10⁰–10⁶ Hz and in the temperature range of 50–300 °C. Powder X-ray diffraction confirms the formation of solid solutions. The dielectric properties were seen to improve with increasing BaTiO₃ (BT) content. The conductivity (AC and DC) measurements reveal an inverse variation of the frequency exponent ‘s’ with temperature, high density of states and thermally activated process. The calculated density of states was found to be N(E_f) = 80.2 × 10³² eV^?1 cm^?1 at 1 kHz and 50 °C for BiFeO₃–10 % BaTiO₃ (BFO–10 % BT) solid solution. The impedance spectroscopy analysis confirms the presence of grain and grain boundary affecting the conductivity. Our results provide the first unambiguous evidence of conduction in crystallite BFO–BT solid solutions through correlated-barrier-hopping model.     

Preparation and Magnetic Properties of CuCr1 – x Mn x S2 Solid Solutions

Phase relations in the CuS–CrS–MnS system (20 mol % MnS) were studied. The system was found to contain CuCr_{1 – x} Mn _x S₂ solid solutions isostructural with CuCrS₂. The solid-solution range and the oxidation states of Cr and Mn were determined.     

Growth mechanisms of intermetallic compounds and Bi-rich layer in ball grid array structure Cu/Sn-58Bi/Cu solder joints during solid–solid and liquid–solid electromigration

Journal of Materials Science: Materials in Electronics - Sn-58Bi solder has attracted much attention due to its low melting temperature and low cost in recent years. However, Sn-58Bi solder might...     

Dielectric properties of BaTiO3–Bi(Zn1/2Ti1/2)O3–NaNbO3 solid solutions

In order to develop dielectric ceramics with temperature-stable permittivity characteristics, perovskite BaTiO₃–Bi(Zn_1/2Ti_1/2)O₃–NaNbO₃ ceramic solid solutions were investigated with a particular focus on effects of BaTiO₃ and NaNbO₃ contents on the dielectric properties of ternary compounds. Keeping the ratios of the other two constituents constant, decreasing the BaTiO₃ content leads to a broadening of the temperature-dependent permittivity maximum and a decrease in the overall permittivity. For compositions of constant BaTiO₃ content, replacing Bi(Zn_1/2Ti_1/2)O₃ with NaNbO₃ shifts the temperature of the maximum permittivity to lower temperatures (e.g., to ?103 °C for a composition of 70BT–5BZT–25NN) while maintaining a broad permittivity peak with temperature, which for the 50BT–25BZT–25NN composition also satisfies the X9R standard. Thus, the investigation of BT–BZT–NN compounds resulted in promising dielectric properties with broad temperature ranges of high permittivity, which is of interest for advanced capacitor applications.     

Physicochemical properties of Nd2-x-yCexSry,CuO4 solid solutions in the range 293–1023 K

The electrical properties and thermal expansion of Nd_2-x-yCe_xSr_yCuO₄ solid solutions were studied in the temperature range 293–1023 K. The temperature dependences of conductivity, dielectric permittivity, and tan δ show anomalies at 488 K for Nd₂Cu0₄ and 400 K for the solid solutions. These anomalies are accompanied by sharp changes in the linear thermal expansion coefficient     

Giant dielectric properties of nanocrystalline Pb1−xSnxF2 solid solutions

Nanocrystalline Pb_1?xSn_xF₂ (x = 0.2, 0.3) solid solutions have been synthesized by mechanochemical milling at room temperature with grain size as small as 26 nm. These fluoride ion conducting materials exhibit giant values of the dielectric constant of ?′ > 10⁵ that is independent of temperature and frequency over wide ranges. The giant values of ?′ are suggested to be due to internal effects in the materials. The dielectric response has been analyzed by appropriate equivalent circuit representing the grain and internal effects in the materials. Interestingly, the dielectric constant of the current samples is found to be larger for the samples with smaller grain size, a behavior that is quite opposite to what usually observed in giant dielectric oxide materials, where ?′ is enhanced with substantial growth of the grain size. The possible origin of the giant dielectric constant is discussed in the present study.     

The AgxCu1−xInS2 solid solutions with 0≤x≤1

The phase equilibriums in the AgInS2–CuInS2 system were investigated by means of X-ray diffraction and differential thermal analysis and the AgInS2 and CuInS2 ternary compounds and the AgxCu1–xInS2 solid solutions were grown by two-zone horizontal method with the following directed crystallization of melt. The T–x phase diagram of this system was constructed and the formation of solid solutions in the complete range of compositions was discovered. The composition dependencies of microhardness, transmission spectra in the range of the fundamental absorption, infrared transmission spectra in the range from 150 to 400 cm-1 for the AgxCu1–xInS2 solid solutions were investigated. It was discovered that the composition dependence of microhardness is expressed by smooth curve having maximum for x=0.2. The composition dependencies of band gap have been analytically expressed at 77 and 293 K for the Ec and Ec direction of polarization and have non-linear behaviour. From the studies of the infrared transmission spectra the frequencies of optical phonons were determined and it was discovered that their composition dependence shows single mode behaviour.     

δ-FeO(OH) and its solid solutions

A transmission electron microscope imaging investigation was performed on small -FeO(OH) crystallites less than 50 Å thick and several hundred angstroms across. We have observed faceting, and a hexagonal plate-like morphology with topological features near atomic step heights. Because of the mutual magnetic attraction on these particles, they tend to align with their thin direction (c-axis) either parallel or perpendicular to the support film surface. It is therefore possible to view dislocations or buckling of lattice planes of these plates either edge-on or perpendicular to this direction by direct lattice imaging in both the bright-field and dark-field modes. A highly distorted lattice is apparent when viewing the particles edge-on, and it is possible to show lattice projections to a resolution of 2.1 Å.     

δ-FeO(OH) and its solid solutions

-FeO(OH)-type solid solutions have been synthesized with compositions Fe_1–x M _x O_1–x (OH)_1+x ranging up tox=0.10 for M=Ca,x=0.35 for M=Mg or Cd andx=0.40 for M=Zn. The phases are characterized by X-ray diffraction and transmission electron microscope studies. A structural model giving satisfactory intensity agreement is postulated for Fe_1–x Zn _x O_1–x (OH)_1+x . In this model, Zn²⁺ ions are situated in the 0 0 0 octahedral sites of space group D _3d ³ -P¯3ml while the Fe³⁺ ions are almost equally distributed among both octahedral sites (0 0 0 and 0 0 1/2).     

Synthesis of Cu2ZnSnS4 films from sequentially electrodeposited Cu–Sn–Zn precursors and their structural and optical properties

The Cu₂ZnSnS₄ (CZTS) films are successfully prepared using a process of sequentially electrodeposited Cu–Sn–Zn precursors by a novel electrolyte formula and optimized parameters on Mo substrate, succeeded by annealing in saturated sulfur atmosphere. The results show that the Cu/Sn/Zn precursor sequence is strict, and optimized electro-deposition parameters are as follows: ?0.6 V, 5 min for Cu, ?1.2 V, 2 min for Sn, and ?1.35 V, 10 min for Zn. Layered precursors firstly alloy into Cu₆Sn₅ and CuZn binary phases under low annealing temperature. Then Cu₆Sn₅ and CuZn alloys decompose in sulfur atmosphere, and form CuS, SnS and ZnS binary phases. Cu₂SnS₃ ternary phase forms through reaction between CuS and SnS with increasing the temperature. Finally, the CZTS film is synthesized through reaction among binary and ternary sulfides. The photoluminescence peak from the CZTS films synthesized at 550 °C for 1 h is about at 1.49 eV.