Crystallization behaviour and phase coexistence at morphotrophic phase boundaries in PZT thin films prepared by sol-gel processing

Pb(Zr_0.53Ti_0.47)O₃ (PZT) thin films, prepared by sol-gel techniques and deposited on to Si/SiO₂/Ti/Pt substrates, have been subjected to thermal annealing in a range of temperatures from 550–800 °C. The crystallization behaviour and phase coexistence (tetragonal and rhombohedral) were studied by X-ray diffraction. According to the values of the {110} peak intensity and {110} peak values, the crystallization full-width at half-maximum was more complete at higher temperatures (750, 800 °C). At a fixed Zr/Ti ratio close to the morphotropic phase boundary, the lattice parameters of the two phases changed with the annealing temperature. However, the tetragonality degree had relatively low values and the angular rhombohedral distortion was associated with a narrow angular range. The phase coexistence and the variation of the lattice parameters could be explained by the titanium diffusion through the platinum layer. Thus the formation of a {0 1 1} titanium rich layer at Pt-PZT interface will supply a titanium excess for the nucleation and growth of textured PZT grains.     

Effect of reduction rate and annealing temperature on texture evolution and magnetic properties of used non-oriented silicon steel

This paper discusses the method of improving the magnetic properties of used silicon steel by cold rolling and annealing process with used non-oriented silicon steel as the object. The texture evolution and magnetic domain structure are also investigated. Experimental results show that the magnetic domain can be transformed vastly compared with the used silicon steel when the specimens are prepared through the same cold rolling and annealing conditions. The length of the magnetic wall and the density of magnetic domain per unit area are boosted, and the magnetic domain refinement is exceedingly apparent. Under the same annealing condition (at 950 °C for 5 min), the γ-fiber is gradually decreased to 6.6 % and the {110} recrystallization texture is gradually enhanced with increased reduction from 28.3 % to 40 %. The intensity of the Goss texture reaches a maximum of 22.2. For the cold rolling reduction of 34.3 %, the γ-fiber gradually decrease to 13.8 % and the {110} recrystallization texture is gradually enhanced with increase in the annealing temperature from 800 °C to 950 °C. Moreover, the intensity of Goss texture reaches 14. The sample prepared through 40 % reduction and annealing at 950 °C for 5 min exhibited the most desirable magnetic properties. The magnetic induction B₅₀ value of the specimen is increased by 0.052 T, and the core loss P_1.5/50 is reduced by 0.478 W/kg compared with the initial specimen.     

Neutron Powder Diffraction Study in La<Subscript>0.85</Subscript>Ag<Subscript>0.15</Subscript>MnO<Subscript>3</Subscript>

La_0.85Ag_0.15MnO₃, the colossal magnetoresistance compound was prepared and the neutron powder diffraction patterns at different temperatures down to 19 K were recorded to study their crystal structure and magnetic properties. These patterns were analyzed by the Rietveld refinement technique and are found to be free from any impurity phase. The compound is found to crystallize in a mixture of R[`3]cR\overline{3}c and Pnma space group and the phase fraction is found to vary with temperature. A cross-over from R[`3]cR\overline{3}c dominated high temperature phase to Pnma dominated low temperature phase at around 130 K was observed. At low temperatures, especially below 285 K, the diffraction patterns could be refined by including the magnetic reflections corresponding to ferromagnetic structure. The refined magnetic moment of Mn ions is found to be along b axis of the unit cell with a maximum moment of 3.74 μ_B at 19 K and this value is comparable to the saturation magnetization observed at 20 K from magnetization measurement.     

High magnetic field effect on texture and grain growth of GNO silicon steel

Magnetic annealing at 800 °C for 3, 15 and 30 minutes was conducted to evaluate the effect of a 17T magnetic field on the microstructure formation of cold rolled Fe‐0.75 %Si samples. According to texture measurements magnetic field did not seem to significantly affect the development of grains with Goss orientation, however it showed to affect the nucleation and growth process of {001}, {110} and {111} grains by increasing the volume fraction of the η fiber and by decreasing the fraction of the alfa and gamma fibers. ESEM/OIM and optical microscope results indicate that although magnetic field may retard nucleation it also promotes grain boundary displacement and for longer annealing times the retardation effect is compensated by the magnetic filed driving force.     

Texture evolution in an Al–Cu alloy during equal channel angular pressing: the effect of starting microstructure

In this article, the effect of initial microstructure on the texture evolution in 2014 Al alloy during equal channel angular pressing (ECAP) through route A has been reported. Three heat treatment conditions were chosen to generate the initial microstructures, namely (i) the recrystallization anneal (as-received), (ii) solution treatment at 768 K for 1 h, and (iii) solution treatment (768 K for 1 h) plus aging at 468 K for 5 h. Texture analyses were performed using orientation distribution function (ODF) method. The texture strength after ECAP processing was different for the three samples in the order, solutionised > solutionised plus aged condition > as-received. The prominent texture components were A _E /[`(A)]<sub>E</sub> \bar{A}_{E} and B <sub>E</sub> /[`(B)]_E \bar{B}_{E} in addition to several weaker components for the three materials. The strong texture evolution in solutionised condition has been attributed to higher strain hardening of the matrix due to higher amount of solute. In case of the as-received as well as solutionised plus aged alloy, the weaker texture could be due to the strain scattering from extensive precipitate fragmentation and dissolution during ECAP.     

In-situ synchrotron x-ray study of the crystallization behavior of Ce0.9La0.1O2 − x thin films deposited on NiW alloy substrates by chemical solution method

The phase and texture formation of La doped CeO₂ (CLO) films deposited by the chemical solution method are studied by in situ synchrotron x-ray diffraction. It is found that the CLO crystallites forms excellent in-plane texture as soon as the phase appears at 860 °C, indicating that interfacial nucleation dominates at the beginning of the amorphous–crystallization transition. Grain growth is almost complete after at 900 °C for 15 min. Analysis of the isothermal process of crystallization at 900 °C by the Johnson–Mehl–Avrami–Kolmogorov equation shows that grain development is mainly controlled by diffusion. The success of this work demonstrates the possibility of studying crystallization behaviors of solution derived films using a non-destructive method, which has the potential of being applicable to most types of thin film samples.     

EBSD Investigation on Oriented Nucleation in IF Steels

The mechanism responsible for the formation of recrystallization texture in cold-rolled Ti bearing interstitial free （IF） steel sheets was investigated using electron back-scatter diffraction （EBSD）. In addition, the origin of nuclei with specific orientations was studied. The formation of recrystallization texture was explained by oriented nucleation. Most nuclei have a high misorientation angle of 25-55° with the surrounding deformed matrices, but no specific orientation of misorientation axis between the nucleus and the surrounding deformed matrix is observed. The stored energy of deformed grains is in the decreasing order of the {111}〈112〉,{111}〈110〉, {112}〈110〉 and {001}〈110〉 orientations. New {111}〈110〉 grains are nucleated within deformed {111}〈112〉 grains and new {111}〈112〉 grains originate in the deformed {111}〈110〉 grains.     

Reduction of a NiO thin film deposited by PLD on a single crystal YSZ (111) substrate

The NiO/YSZ interface prepared by depositing NiO on a single crystal YSZ (111) substrate has been investigated by transmission electron microscopy. As deposited, a very thin nickel layer ascribing to the nonstoichiometry at the very beginning growth of NiO and an amorphous silica phase resulting from silicon segregation were present at the interface. The orientational relationship of NiO (1[`1] 1) (1\overline{1} 1) //Ni (1[`1] 1) (1\overline{1} 1) //YSZ (1[`1] 1) (1\overline{1} 1) with NiO [110]//Ni [110]//YSZ [110] was observed. The microstructural and chemical changes at the NiO/YSZ interface after being heated in vacuum and hydrogen indicated different reduction mechanisms. In vacuum, the reaction \textNiO ? \textNi + 1/ 2 \text O ₂ ( \textg ) {\text{NiO}} \to {\text{Ni}} + 1/ 2 {\text{ O}}_{ 2} \left( {\text{g}} \right) was prevailing at the interface between NiO and pre-existing Ni, which led to the thickening of nickel layer. In hydrogen, the reduction initiated on the NiO surface was dominant, following the chemical equation H₂ + O_O (NiO) → H₂O (g) + V_O ^.. (NiO) + 2e (Ni).     

Phase and morphology evolution of calcium carbonate precipitated by carbonation of hydrated lime

Phase and morphology evolution of CaCO₃ precipitated during carbonation of lime pastes via the reaction Ca(OH)₂ + CO₂ → CaCO₃ + H₂O has been investigated under different conditions (pCO₂ ≈ 10^−3.5 atm at 60 % RH and 93 % RH; pCO₂ = 1 atm at 93 % RH) using XRD, FTIR, TGA, and SEM. Simulations of the pore solution chemistry for different stages and conditions of carbonation were performed using the PHREEQC code to investigate the evolution of the chemistry of the system. Results indicate initial precipitation of amorphous calcium carbonate (ACC) which in turn transforms into scalenohedral calcite under excess Ca²⁺ ions. Because of their polar character, { 21[`3]4 } \left\{ {21\bar{3}4} \right\} scalenohedral faces (type S) interact more strongly with excess Ca<sup>2+</sup> than non-polar { 10[`1]4 } \left\{ {10\bar{1}4} \right\} rhombohedral faces (type F), an effect that ultimately favors the stabilization of { 21[`3]4 } \left\{ {21\bar{3}4} \right\} faces. Following the full consumption of Ca<sup>2+</sup> ions and further dissolution of CO<sub>2</sub> leading to a pH drop of the pore solution, { 21[`3]4 } \left\{ {21\bar{3}4} \right\} scalenohedra are subjected to dissolution. This eventually results in re-precipitation of { 10[`1]4 } \left\{ {10\bar{1}4} \right\} rhombohedra at close-to-neutral pH. This crystallization sequence progresses through the carbonated depth with a strong dependence on the degree of exposure to CO₂, which is controlled by the carbonated pore structure governing the diffusion of CO₂. Both the carbonation process and the scalenohedral-to-rhombohedral transformation are kinetically favored under high RH and high pCO₂. Supersaturation plays a critical role on the nucleation density and size of CaCO₃ crystals. These results have important implications in understanding the behavior of ancient and modern lime mortars for applications in architectural heritage conservation.     

Texture evolution during inclined cold rolling of used non-oriented silicon steel

With the objective of optimizing the texture components and exploring a method to improve the magnetic properties of used silicon steel, the methods of one inclined rolling and two inclined rolling were applied. The result shows: the new Goss grains were nucleated except at {111} deformed grains, and also formed at the grain boundary between two deformed grains with {113} orientation, and at grains boundaries between {113} and {100} deformed grain. The grain size after one inclined rolling (57 %) was larger and more homogeneous than the grain size after the two inclined rolling. Although with different cold rolling methods (one and two inclined rolling), the resulted annealing textures all had similar features. The difference was the relative intensities between the main texture. A significant feature of one inclined rolling was the intensification of the η-fiber and the Goss texture component and the weakening of γ-fiber. At an inclination angle of 60°, a significantly strong Goss texture was produced, which was highest among all samples, and the maximum volume fraction of {110}+{100} texture can also be obtained. One inclined rolling can better improve the magnetic properties of used silicon steel (B₅₀), and the magnetic induction is between 1.712 T and 1.742 T. The highest magnetic induction of 1.742 T can be obtained by one inclined rolling (at an inclination angle of 60°).     

Epitaxial growth of CoSi2 on Si(001) by reactive deposition epitaxy: Island growth and coalescence

Epitaxial CoSi₂ layers, which are phase pure but contain {111} twins, are grown on Si(001) at 700 °C by reactive deposition epitaxy. Transmission electron microscopy analyses show that the initial formation of CoSi₂(001) follows the Volmer-Weber mode characterized by the independent nucleation and growth of three-dimensional islands whose evolution we follow as a function of deposited Co thickness t_Co in order to understand the origin of the observed twin density. We find that there are two families of island shapes: inverse pyramids and platelets. The rectangular-based pyramidal islands extend along orthogonal 〈110〉 directions, bounded by four {111} CoSi₂/Si interfaces, and grow with a cube-on-cube orientation with respect to the substrate: (001)_CoSi2||(001)_Si and [100]_CoSi2||[100]_Si. Platelet-shaped CoSi₂ islands are bounded across their long 〈110〉 directions by {111} twin planes (i.e. {111}(001)_CoSi2||{111}_Si) and their narrow 〈110〉 directions by {511}_CoSi2||{111}_Si interfaces. The top and bottom surfaces are {22¯1}, with {22¯1}_CoSi2||(001)_Si, and {1¯1¯1}, with {1¯1¯1}_CoSi2||{11¯1}_Si, respectively. The early stages of film growth (t_Co ≤ 13 Å) are dominated by the twinned platelets due to a combination of higher nucleation rates resulting from a larger number of favorable adsorption sites in the Si(001)2 × 1 surface unit cell and rapid elongation of the platelets along preferred 〈110〉 directions. However, at t_Co ≥ 13 Å island coalescence becomes significant as orthogonal platelets intersect and block elongation along fast growth directions. In this regime, where both twinned and untwinned island number densities have saturated, further island growth becomes dominated by the untwinned islands. A continuous epitaxial CoSi₂(001) layer, with a twin density of 2.8 × 10¹⁰ cm^− 2, is obtained at t_Co = 50 Å.     

Preparation of nanocrystalline LiMnPO<Subscript>4</Subscript> via a simple and novel method and its isothermal kinetics of crystallization

The precursor of nanocrystalline LiMnPO₄ was obtained by solid-state reaction at low heat using Li₂SO₄·H₂O, MnSO₄·H₂O, and Na₃PO₄·12H₂O as raw materials, maintaining the mixture at 333 K for 4 h, and then washing the mixture with deionized water to remove soluble inorganic salts, and at last drying at 373 K. The nanocrystalline LiMnPO₄ was obtained by calcining the precursor. The precursor and its calcined products were characterized using TG/DTA, FT-IR, and XRD. The data showed that the precursor dried at 373 K for 3 h was a compound with amorphous structure. However, when the precursor was calcined at 973 K for 2 h, highly crystallization LiMnPO₄ with orthorhombic structure [space group Pmnb (62)] was obtained with a crystallite size of 38 nm. The mechanism and kinetics of the crystallization process of LiMnPO₄ were studied using XRD technique, the results showed that activation energy of the crystallization process of LiMnPO₄ was 103.30 kJ/mol, and the mechanism of crystallization process of LiMnPO₄ is the random nucleation and growth of nuclei reaction.     

Growth of crystallized Ge films from VHF inductively-coupled plasma of H2-diluted GeH4

We have studied the Ge crystalline nucleation and film growth on quartz substrate at 250 °C from inductively-coupled plasma (ICP) of GeH₄ diluted with H₂. The ICP was generated by supplying 60 MHz power to an external single-turn antenna which was placed on a quartz plate window of a stainless steel reactor and parallel to the substrate. We have found that the growth rate is significantly increased when the preferential growth of the (110) plane becomes pronounced after the formation of randomly-oriented crystalline network. The (110) oriented Ge films, of which average crystallinity is as high as 70%. The integrated intensity ratio of TO phonons in crystalline phase to those in disordered phase, were grown at a rate of ∼ 4.0 nm/s after the formation of amorphous incubation layer with a thickness of ∼ 0.1 μm on quartz.     

The development of <100> texture in Fe-Cr-Co-Mo permanentmagnet alloys

The cold-rolled and recrystallization textures of Fe-Cr-Co-Mo permanent magnet alloys are described. The studied composition is Fe-30%Cr-15%Co-3%Mo (in wt.%). The cold-rolled texture can be considered to be {111}<110>, {111}<112>, {100}<110>, and {211}<110>, while the recrystallization texture can be considered to be {111}<100>, {110}<112>, {211}<110>, and {110}<110>. The secondary recrystallization is caused by heat-treating the alloys in the sequence of α, α+γ, α+γ+σ, α phase region. This results in a favorable texture of {110}<110> and <100> direction, aligning along the transverse direction (TD) of the strips. The best magnetic properties obtained in this study were 1.2 T (12.0 kG), iH _c=82.0 kAm^-1 (1025 Oe), and (BH)max= 60.8 kJm^-3 (7.6 MGOe) with TD alloys     

Grain morphology and texture evolution of TC21 titanium alloy during annealing with different time

A homogeneous equiaxed‐structure TC21 titanium alloy is hot rolled and annealed for different time ranging from 1 h to 6 h. The grain morphology and texture evolution of α and β phases during annealing are mainly investigated using the electron back‐scattered diffraction characterization. In the early annealing stage, the α grain mainly maintains the elongated morphology generated in the rolling. With increasing annealing time, more and more elongated α grains become equiaxed due to enhanced static recrystallization and boundary splitting. Differently, the β grain exhibits a fully equiaxed morphology all the time due to the sufficient static recrystallization, and get a coarsening with increasing annealing time. The α phase exhibits a (0001) basal texture in the early annealing stage, and then forms a TD‐split texture with increasing annealing time. The β phase exhibits the {001}<110> texture at every annealing time. Based on the analysis about the texture of different grain sizes, the effects of recrystallization nucleation and oriented growth on texture evolution are discussed. It suggests that TD‐split texture in α phase is originated from both the recrystallization nucleation and oriented growth. The formation of {001}<110> texture in β phase is mainly originated from the oriented growth.     

Characterization of microstructure,texture and magnetic properties in twin-roll casting high silicon non-oriented electrical steel

An Fe-6.5 wt.% Si-0.3 wt.% Al as-cast sheet was produced by twin-roll strip casting process, then treated with hot rolling, warm rolling and annealing. A detailed study of the microstructure and texture evolution at different processing stages was carried out by optical microscopy, X-ray diffraction and electron backscattered diffraction analysis. The initial as-cast strip showed strong columnar grains and pronounced < 001 >//ND texture. The hot rolled & warm rolled sheets were characterized by large amounts of shear bands distributed through the thickness together with strong < 110 >//RD texture and weak < 111 >//ND texture. After annealing, detrimental < 111 >//ND texture almost disappeared while beneficial {001}<210 >, {001}<010 >, {115}<5 − 10 1 > and {410} < 001 > recrystallization textures were formed, thus the magnetic induction of the annealed sheet was significantly improved. The recrystallization texture in the present study could be explained by preferred nucleation and grain growth mechanism.     

SAXS study on crystallization of an amorphous Pd76Au6Si18 alloy

The crystallization behaviour of an amorphous Pd₇₆Au₆Si₁₈ alloy has been investigated mainly by means of small angle X-ray scattering measurements. The amorphous alloy crystallized to form MS-I phase with composition Pd₇₈Au₂₂ in the amorphous matrix, which later crystallized as MS-II. The crystallization kinetics of MS-I phase were analysed in the framework of conventional nucleation theory. It was suggested that the considerable number of nuclei of MS-I phase had been already formed in the as-quenched specimen and the remaining nucleation attained within the short period of isothermal ageing. The remarkable increase of the scattering intensity corresponded to the growth of MS-I phase, the kinetics of which were found to be controlled by the diffusion mechanism. The interdiffusion constant was obtained fromD=6.0×10¹⁵ exp (–420 kJ mol^–1/RT) m² sec^–1, which agreed fairly with the reported values.     

Preparation and ferroelectric properties of (124)-oriented SrBi<Subscript>4</Subscript>Ti<Subscript>4</Subscript>O<Subscript>15</Subscript> ferroelectric thin film on (110)-oriented LaNiO<Subscript>3</Subscript> electrode

A (124)-oriented SrBi₄Ti₄O₁₅ (SBTi) ferroelectric thin film with high volume fraction of was obtained using a metal organic decomposition process on SiO₂/Si substrate coated by (110)-oriented LaNiO₃ (LNO) thin film. The remanent polarization (P _r) and coercive field (E _c) for (124)-oriented SBTi film are 12.1 μC/cm² and 74 kV/cm, respectively. No evident fatigue of (124)-oriented SBTi thin film can be observed after 1 × 10⁹ switching cycles. Besides, the (124)-oriented SBTi film can be uniformly polarized over large areas using a piezoelectric-mode atomic force microscope. Considering that the annealing temperature was 650 °C and the thickness of each deposited layer was merely 30 nm, a long-range epitaxial relationship between SBTi(124) and LNO(110) facets was proposed. The epitaxial relationship was demonstrated based on the crystal structures of SBTi and LNO.     

Microstructure and texture of Al coating during kinetic spraying and heat treatment

Microstructure and texture formation of an Al coating during kinetic spraying (or cold gas dynamic spraying) and heat treatment were investigated. Coating formation by kinetic spraying is based on super-sonic collision of in-flight micron-sized particles and their severe interfacial plastic deformation under ultra-high strain rates (1.0 × 10⁶–0.5 × 10⁹ s⁻¹), which induces adiabatic shear instability. Shear texture, 45°-rotated Cube {001} <110>, and static recovered microstructure were formed at the interface of Al during kinetic spraying because Al has the equivalent slip system {111} <110> of a face-centered cubic having high stacking fault energy (SFE). During heat treatment, discontinuous recrystallization and grain growth led to transformation of the shear texture into a strong Cube texture, {001} <100>, and misorientation angle transition. Given the mechanical and physical properties of the Al, metallurgical mechanisms of microstructure and texture formation of kinetic-sprayed and heat-treated Al coatings were suggested based on transmission electron microscopy and electron backscatter diffraction analysis.     

Effect of magnetic iron impurity on the superconducting properties of an amorphous Nb50Zr35Si15 alloy

The effect of magnetic iron impurity on the superconducting properties of amorphous Nb₅₀Zr_35−x Si₁₅Fe _x (x⩽4 at %) alloys was examined. Doping with an iron impurity resulted in a linear depression ofT _c andH _c2(T) and a decrease in andρ _n after reaching a maximum value at 0.5 to 1.0 at % iron. The observed decrease was about 35% forT _c, 85% forH _c2 at 2.0 K, 16% for and 21% forρ _n. Although the decrease in occurs through the decrease inρ _n as expected from the GLAG theory, the depression inT _c caused by magnetic impurity could not be explained in terms of the GLAG theory which is applicable to Nb-Zr-Si amorphous alloys without magnetic impurity, but was interpreted as arising from the pair-breaking effect in the superconducting nature due to magnetic scattering. However, the pair-breaking effect was found to be smaller by about one-tenth for the present amorphous superconductors than for crystalline superconductors, indicating the high stability of the superconductivity of the Nb-Zr-Si-Fe alloys against the magnetic scattering arising from the magnetic impurity. The reduced magnetic field at which the reduced fluxoid pinning force exhibits a maximum value increased with iron concentration, indicative of an enhancement of fluxoid pinning force. The enhancement in fluxoid pinning force was interpreted as arising from the increase in compositional, electronic and/or magnetic fluctuations by the dope of iron impurity.