Search results for "general [BL Lacertae objects]"
showing 10 items of 27644 documents
Induced crystallographic changes in Cd1−xZnxO films grown on r-sapphire by AP-MOCVD: the effects of the Zn content when x ≤ 0.5
2020
High-resolution X-ray diffraction, scanning electron microscopy and transmission electron microscopy techniques were used to investigate, as a function of the nominal Zn content in the range of 0–50%, the out-of-plane and in-plane crystallographic characteristics of Cd1−xZnxO films grown on r-plane sapphire substrates via atmospheric pressure metal–organic chemical vapor deposition. The study is conducted to search for knowledge relating to the structural details during the transition process from a rock-salt to a wurtzite structure as the Zn content increases in this CdO–ZnO system. It has been found that it is possible to obtain films exhibiting a single (001) cubic orientation with good …
Enhancement of the dielectric response through Al-substitution in La1.6Sr0.4NiO4 nickelates
2016
The structures and dielectric properties of La1.6Sr0.4Ni1−xAlxO4 (x = 0, 0.2 and 0.4) ceramics elaborated using the Pechini method were studied for the first time. The same unique tetragonal phase was found in all compounds. The lattice parameters were found using Rietveld refinement. The surface morphology characterization and elemental analysis of these samples were respectively carried out using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). A giant dielectric response was observed in these ceramics, and one dielectric relaxation was found. The substitution of nickel with aluminum results in a colossal dielectric constant value (>106). The dielectric l…
Evaluation of nano/submicro pores in suspension plasma sprayed YSZ coatings
2019
Abstract Nano-submicro pores could considerably influence the coating performances and thus should be properly designed for the intended applications. However, it is challenging to characterize accurately such small pores in coatings. In this study, YSZ coatings were firstly manufactured by suspension plasma spray (SPS) and the nano-submicro pores in as-prepared coatings were investigated using Ultra-small-angle X-ray scattering (USAXS). Afterwards, a multivariate analysis on the effect of five different process parameters was carried out. The two main results showed that: 1) the nano-submicro pores content in coatings has a negative correlation with suspension mass load and powder size, an…
Effect of oxidation post treatments on TiO2 coating manufactured using reactive very low-pressure plasma spraying (R-VLPPS)
2020
Abstract TiO2 coatings manufactured using reactive very low-pressure plasma spraying (R-VLPPS) were analyzed in different regions related to their position compared to the plasma flame. For that, a screen was used in order to hide an area of the substrate from the direct plasma flux. The coating morphology changed from quasi lamellar structure to highly vapor structure and coatings exhibited obvious modifications in terms of phases and mechanical properties. The effect of oxidation post treatment on the as sprayed coating was then studied by selecting two methods: in situ oxidation post treatment and classical thermal treatment. The two post treatments provided an increase of the main rutil…
Selective Band Gap to Suppress the Spurious Acoustic Mode in Film Bulk Acoustic Resonator Structures
2018
In this work, we investigate numerically the propagation of Lamb waves in a film bulk acoustic resonator (FBAR) structure formed by piezoelectric ZnO layer sandwiched between two Mo electrodes coupled with Bragg reflectors; the system is thus considered as a phononic-crystal (PnC) plate. The aim is to suppress the first-order symmetric Lamb wave mode considered as a spurious mode caused by the establishment of a lateral standing wave due to the reflection at the embedded lateral extremities of the structure; this spurious mode is superposing to the main longitudinal mode resonance of the FBAR. The finite element study, using harmonic and eigen-frequency analyses, is performed on the section…
Evaluation and Comparison of Novel Precursors for Atomic Layer Deposition of Nb2O5 Thin Films
2012
Atomic layer deposition (ALD) of Nb2O5 thin films was studied using three novel precursors, namely, tBuN═Nb(NEt2)3, tBuN═Nb(NMeEt)3, and tamylN═Nb(OtBu)3. These precursors are liquid at room temperature, present good volatility, and are reactive toward both water and ozone as the oxygen sources. The deposition temperature was varied from 150 to 375 °C. ALD-type saturative growth modes were confirmed at 275 °C for tBuN═Nb(NEt2)3 and tBuN═Nb(NMeEt)3 together with both oxygen sources. Constant growth rate was observed between a temperature regions of 150 and 325 °C. By contrast, amylN═Nb(OtBu)3 exhibited limited thermal stability and thus a saturative growth mode was not achieved. All films we…
Atomic Layer Deposition of Osmium
2011
Growth of osmium thin films and nanoparticles by atomic layer deposition is described. The Os thin films were successfully grown between 325 and 375 °C using osmocene and molecular oxygen as precursors. The films consisted of only Os metal as osmium oxides were not detected in X-ray diffraction measurements. Also the impurity contents of oxygen, carbon, and hydrogen were less than 1 at % each at all deposition temperatures. The long nucleation delay of the Os process facilitates either Os nanoparticle or thin film deposition. However, after the nucleation delay of about 350 cycles the film growth proceeded linearly with increasing number of deposition cycles. Also conformal growth of Os thi…
Atomic Layer Deposition of LiF Thin Films from Lithd, Mg(thd)2, and TiF4 Precursors
2013
Lithium fluoride is an interesting material because of its low refractive index and large band gap. Previously LiF thin films have been deposited mostly by physical methods. In this study a new way of depositing thin films of LiF using atomic layer deposition (ALD) is presented. Mg(thd)2, TiF4 and Lithd were used as precursors, and they produced crystalline LiF at a temperature range of 300–350 °C. The films were studied by UV–vis spectrometry, field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), atomic force microscopy (AFM), time-of-flight elastic recoil detection analysis (ToF-ERDA), and energy dispersive X-ray spectroscopy (EDX). In addition, film adhesion was t…
Non-Linearity Extremum in Niobium Doped Potassium Tantalate
1997
We report non-linear dielectric measurements in the KTaO 3 :Nb system (x Nb ≤ 0.05). The non-linear susceptibility diverges at low temperatures and reaches maximum values in the intermediate range (0.0075 ≤ x Nb ≤ 0.02). To account for this extremum non linearity, we propose a model of temperature dependent clusters which fits with a number of experimental reports. We also suggest that this model may be applied to the related compounds SrTiO 3 :Ca and KTaO 3 :Na.
Electromechanical properties of Na 0.5 Bi 0.5 TiO 3 -SrTiO 3 -PbTiO 3 solid solutions
2018
Abstract Thorough studies of electric field-induced strain are presented in 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3 (NBT-ST-PT) ternary solid solutions. The increase of concentration of lead x induces crossover from relaxor to ferroelectric. Strain in a relaxor state can be described by electrostrictive behavior. The electrostrictive coefficients correspond to other well-known relaxor ferroelectrics. The concentration region with a stable ferroelectric phase revealed that the polarization dependence of strain does not exhibit nonlinearity, although they are inherent to the electric field dependence of strain. In this case, electric field dependence of strain is described in terms of the Ray…