In situ synthesis and properties of self-reinforced $$\hbox {Si}_{3} \hbox {N}_{4}\textendash \hbox {SiO}_{2}\textendash \hbox {Al}_{2} \hbox {O}_{3}\textendash \hbox {Y}_{2}\hbox {O}_{3} \ (\hbox {La}_{2}\hbox {O}_{3}$$) glass–ceramic composites

In-situ-grown \(\upbeta \!\hbox {-Si}_{3}\hbox {N}_{4}\)-reinforced \(\hbox {SiO}_{2}\textendash \hbox {Al}_{2}\hbox {O}_{3}\textendash \hbox {Y}_{2}\hbox {O}_{3}\) \((\hbox {La}_{2}\hbox {O}_{3})\) self-reinforced glass–ceramic composites were obtained without any \(\upbeta \!\hbox {-Si}_{3}\hbox {N}_{4}\) seed crystal. These composites with different compositions were prepared in a nitrogen atmosphere for comparison of phase transformation and mechanical properties. The results showed that \(\hbox {SiO}_{2}\textendash \hbox {Al}_{2}\hbox {O}_{3}\textendash \hbox {Y}_{2}\hbox {O}_{3}\) \((\hbox {La}_{2}\hbox {O}_{3})\) glass can effectively promote \(\upalpha \)- to \(\upbeta \!\hbox {-Si}_{3}\hbox {N}_{4}\) phase transformation. The crystallized \(\hbox {Y}_{2}\hbox {Si}_{2}\hbox {O}_{7}\textendash \hbox {La}_{4.67}\hbox {Si}_{3}\hbox {O}_{13}\) phases with a high melting point significantly benefited the high-temperature mechanical properties of the composites. The \(\hbox {Si}_{3}\hbox {N}_{4}\textendash \hbox {SiO}_{2}\textendash \hbox {Al}_{2} \hbox {O}_{3}\textendash \hbox {Y}_{2}\hbox {O}_{3}\) \((\hbox {La}_{2}\hbox {O}_{3})\) glass–ceramic composites exhibit excellent mechanical properties compared with unreinforced glass–ceramic matrix, which is undoubtedly attributed to the elongated \(\upbeta \!\hbox {-Si}_{3}\hbox {N}_{4}\) grains. These glass–ceramic \(\hbox {Si}_{3}\hbox {N}_{4}\) composites with excellent comprehensive properties might be a promising material for high-temperature applications.     

Strain-induced structural,magnetic and ferroelectric properties of heterostructure BST–NZFO nanocomposite thin film at room temperature

Heterostructure \(\hbox {Ba}_{0.7}\hbox {Sr}_{0.3}\hbox {TiO}_{3}\)–\(\hbox {Ni}_{0.8}\hbox {Zn}_{0.2}\hbox {Fe}_{2}\hbox {O}_{4}\) composite thin films grown on Pt–\(\hbox {TiO}_{2}\)–\(\hbox {SiO}_{2}\)–\(\hbox {Si}\) substrate were prepared by chemical solution process, where \(\hbox {Ba}_{0.7}\hbox {Sr}_{0.3}\hbox {TiO}_{3}\) layer grew as top/bottom while \(\hbox {Ni}_{0.8}\hbox {Zn}_{0.2}\hbox {Fe}_{2}\hbox {O}_{4}\) layer grew as bottom/top. Structural characterization by X-ray diffraction and atomic force microscopy showed the similar crystal structure, different lattice parameters, large lattice strain and small grain size in heterostructures, whatever their deposition sequences. Such heterostructures present simultaneously ferromagnetic and ferroelectric responses at room temperature. In particular, an exceptionally large saturation magnetization was observed in one heterostructures film. The growth sequences of \(\hbox {Ba}_{0.7}\hbox {Sr}_{0.3}\hbox {TiO}_{3}\) and \(\hbox {Ni}_{0.8}\hbox {Zn}_{0.2}\hbox {Fe}_{2}\hbox {O}_{4}\) layers on the substrate remarkably affect the magnetic properties of the composite thin films at room temperature.     

Structural stability and magnetic properties of $$\hbox {Cu}_{m}\hbox {Co}_{n}\hbox {NO}$$ ($$m+n = 2$$m+n=2–7) clusters

A theoretical study of NO adsorption on \(\hbox {Cu}_{m}\hbox {Co}_{n}\) (2 \(\le m+n \le \) 7) clusters was carried out using a density functional method. Generally, NO is absorbed at the top site via the N atom, except in \(\hbox {Cu}_{3}\hbox {NO}\) and \(\hbox {Cu}_{5}\hbox {NO}\) clusters, where NO is located at the bridge site. \(\hbox {Co}_{2}\hbox {NO}\), \(\hbox {Co}_{3}\hbox {NO}\), \(\hbox {Cu}_{2}\hbox {Co}_{2}\hbox {NO}\), \(\hbox {Co}_{5}\hbox {NO}\), \(\hbox {Cu}_{2}\hbox {Co}_{4}\hbox {NO}\) and \(\hbox {Cu}_{6}\hbox {CoNO}\) clusters have larger adsorption energies, indicating that NO of these clusters are more easily adsorbed. After adsorption, N–O bond is weakened and the activity is enhanced as a result of vibration frequency of N–O bond getting lower than that of a single NO molecule. \(\hbox {Cu}_{2}\hbox {CoNO}\), \(\hbox {Cu}_{3}\hbox {CoNO}\), \(\hbox {Cu}_{2}\hbox {Co}_{2}\hbox {NO}\), \(\hbox {Cu}_{3}\hbox {Co}_{3}\hbox {NO}\) and \(\hbox {Cu}\hbox {Co}_{5}\hbox {NO}\) clusters are more stable than their neighbours, while CuCoNO, \(\hbox {Co}_{3}\hbox {NO}\), \(\hbox {Cu}_{3}\hbox {CoNO}\), \(\hbox {Cu}_{2}\hbox {Co}_{3}\hbox {NO}\), \(\hbox {Cu}_{3}\hbox {Co}_{3}\hbox {NO}\) and \(\hbox {Cu}_{6}\)CoNO clusters display stronger chemical stability. Magnetic and electronic properties are also discussed. The magnetic moment is affected by charge transfer and the spd hybridization.     

Elastic and thermodynamic properties of zirconium- and hafnium-doped $$\hbox {Rh}_{3}\hbox {V}$$ intermetallic compounds: potential aerospace material

Structural, electronic, mechanical and thermodynamic properties of \(\hbox {Rh}_{3}\hbox {Zr}_{x}\hbox {V}_{1-x}\) and \(\hbox {Rh}_{3}\hbox {Hf}_{x}\hbox {V}_{1-x}\) (\(x = 0\), 0.125, 0.25, 0.75, 0.875 and 1) combinations are investigated by means of first-principles calculations based on the density functional theory within the generalized gradient approximation. Here, \(\hbox {Rh}_{3}\hbox {V}\) is chosen as the parent binary compound and the doping elements are zirconium and hafnium with the above-mentioned concentrations. The calculated lattice parameters and elastic modulus of binary \(\hbox {Rh}_{3}\hbox {Hf}\), \(\hbox {Rh}_{3}\hbox {V}\) and \(\hbox {Rh}_{3}\hbox {Zr}\) are in good agreement with the available experimental and other theoretical results. In this study, the following ternary materials viz., \(\hbox {Rh}_{3}\hbox {Zr}_{0.75}\hbox {V}_{0.25}\), \(\hbox {Rh}_{3}\hbox {Hf}_{0.25}\hbox {V}_{0.75}\) and \(\hbox {Rh}_{3}\hbox {Hf}_{0.75}\hbox {V}_{0.25}\) are found to be brittle/more brittle than the parent binary compound \(\hbox {Rh}_{3}\hbox {V}\), whereas the other ternary combinations, namely \(\hbox {Rh}_{3}\hbox {Zr}_{0.125}\hbox {V}_{0.875}\), \(\hbox {Rh}_{3}\hbox {Zr}_{0.25}\hbox {V}_{0.75}\), \(\hbox {Rh}_{3}\hbox {Zr}_{0.875}\hbox {V}_{0.125}\), \(\hbox {Rh}_{3}\hbox {Hf}_{0.125}\hbox {V}_{0.875}\) and \(\hbox {Rh}_{3}\hbox {Hf}_{0.875}\hbox {V}_{0.125}\) are found to be more ductile than \(\hbox {Rh}_{3}\hbox {V}\). The more brittle ternary combination, namely \(\hbox {Rh}_{3}\hbox {Hf}_{0.75}\hbox {V}_{0.25}\) (\(B = 229.32\,\hbox {GPa}\)) has the maximum Young’s modulus, shear modulus and hardness values; whereas the more ductile ternary \(\hbox {Rh}_{3}\hbox {Zr}_{0.25}\hbox {V}_{0.75}\) combination (\(B = 243.54\,\hbox {GPa}\)) is found to have the least values of Young’s modulus, shear modulus and hardness. The band structure, density of states histograms and charge density plots are drawn and discussed. Computed Debye temperature (\(\theta _{\mathrm{D}}\)), Grüneisen parameter (\(\zeta \)) and melting temperature (\(T_{\mathrm{m}})\) of the parent binary compound \(\hbox {Rh}_{3}\hbox {V}\), the more brittle \(\hbox {Rh}_{3}\hbox {Hf}_{0.75}\hbox {V}_{0.25}\) combination and the more ductile \(\hbox {Rh}_{3}\hbox {Zr}_{0.25}\hbox {V}_{0.75}\) combination are given by (895 K, 1.3491, 2788 K), (790 K, 1.2701, 2736 K) and (698 K, 1.7972, 2529 K), respectively.     

Synthesis,characterization and electrochemical performance of $$\hbox {Li}_{2}\hbox {Ni}_{x}\hbox {Fe}_{1-x}\hbox {SiO}_{4}$$ cathode materials for lithium ion batteries

\(\hbox {Li}_{2}\hbox {Ni}_{x}\hbox {Fe}_{1-x}\hbox {SiO}_{4}\) (\(x = 0\), 0.2, 0.4, 0.6, 0.8 and 1) samples were prepared by a sol–gel process. The crystal structure of prepared samples of \(\hbox {Li}_{2}\hbox {Ni}_{x}\hbox {Fe}_{1-x}\hbox {SiO}_{4}\) was characterized using an X-ray diffractometer. Different crystallographic parameters such as crystallite size and lattice cell parameters have been calculated. Scanning electron microscopy and Fourier transform infrared spectroscopy investigations were carried out, which reveal the morphology and function groups of the synthesized samples. Furthermore, electrochemical impedance spectra measurements are performed. The obtained results indicated that the highest conductivity is achieved for the \(\hbox {Li}_{2}\hbox {Ni}_{0.4}\hbox {Fe}_{0.6}\hbox {SiO}_{4}\) electrode compound. It was observed that Li–\(\hbox {Li}_{2}\hbox {Ni}_{0.4}\hbox {Fe}_{0.6}\hbox {SiO}_{4}\) battery has initial discharge capacity of 164 mAh \(\hbox {g}^{-1}\) at 0.1C rate. The cycle life performance of all \(\hbox {Li}_{2}\hbox {Ni}_{x}\hbox {Fe}_{1-x}\hbox {SiO}_{4}\) batteries ranged between 100 and 156 mAh \(\hbox {g}^{-1}\) with coulombic efficiency range between 70.9 and 93.9%.     

Effect of annealing temperature and $$\hbox {CdCl}_{2}$$ treatment on the photo-conversion efficiency of $$\hbox {CdTe/Zn}_{0.1}$$CdTe/Zn0.1$$\hbox {Cd}_{0.9}$$Cd0.9S thin film solar cells

We report the effects of annealing in conjunction with \(\hbox {CdCl}_{2}\) treatment on the photovoltaic properties of \(\hbox {CdTe/Zn}_{0.1}\hbox {Cd}_{0.9}\)S thin film solar cells. CdTe layer is subjected to dry \(\hbox {CdCl}_{2}\) treatment by thermal evaporation method and subsequently, heat treated in air using a tube furnace from 400 to \(500{^{\circ }}\hbox {C}\). AFM and XRD results show improved grain size and crystallographic properties of the CdTe film with dry \(\hbox {CdCl}_{2}\) treatment. This recrystallization and grain growth of the CdTe layer upon \(\hbox {CdCl}_{2}\) treatment translates into improved photo-conversion efficiencies of \(\hbox {CdTe/Zn}_{0.1}\hbox {Cd}_{0.9}\)S cell. The results of dry \(\hbox {CdCl}_{2}\) treatment were compared with conventional wet \(\hbox {CdCl}_{2}\) treatment. Photo-conversion efficiency of 5.2% is achieved for dry \(\hbox {CdCl}_{2}\)-treated cells in comparison with 2.4% of wet-treated cell at heat treatment temperature of \(425{^{\circ }}\hbox {C}\).     

Facile synthesis and characterization of rough surface $$\mathrm{V}_{2}\hbox {O}_{5}$$ nanomaterials for pseudo-supercapacitor electrode material with high capacitance

\(\hbox {V}_{2}\hbox {O}_{5}\) nanomaterials with rough surface were synthesized using commercial \(\hbox {V}_{2}\hbox {O}_{5}\), ethanol (EtOH) and \(\hbox {H}_{2}\hbox {O}\) as the starting materials by a simple hydrothermal route and combination of calcination. The electrochemical properties of \(\hbox {V}_{2}\hbox {O}_{5}\) nanomaterials as electrodes in a supercapacitor device were measured using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) method. \(\hbox {V}_{2}\hbox {O}_{5}\) nanomaterials exhibit the specific capacitance of 423 F \(\hbox {g}^{-1}\) at the current density of 0.5 A \(\hbox {g}^{-1}\) and retain 327 F \(\hbox {g}^{-1}\) even at the high current density of 10 A \(\hbox {g}^{-1}\). The influence of the ratio of \(\hbox {EtOH/H}_{2}\hbox {O}\), the calcined time and temperature on the morphology, purity and electrochemical property of the products is discussed in detail. The results revealed that the ratio of \(\hbox {EtOH}\hbox {/}\hbox {H}_{2}\hbox {O}= 10\hbox {/}25\) and calcination at \(400{^{\circ }}\hbox {C}\) for 2–4 h are favourable for preparing \(\hbox {V}_{2}\hbox {O}_{5}\) nanomaterials and they exhibited the best electrochemical property. The novel morphology and high specific surface area are the main factors that contribute to high electrochemical performance of \(\hbox {V}_{2}\hbox {O}_{5}\) nanomaterials during the charge–discharge processes. It turns out that \(\hbox {V}_{2}\hbox {O}_{5}\) nanomaterials with rough surface is an ideal material for supercapacitor electrode in the present work.     

Resistance-switching properties of Bi-doped $$\hbox {SrTiO}_{3}$$ films for non-volatile memory applications with different device structures

\(\hbox {SrTiO}_{3}\) and Bi-doped \(\hbox {SrTiO}_{3}\) films were fabricated with different device structures using the sol–gel method for non-volatile memory applications, and their resistance-switching behaviour, endurance and retention characteristics were investigated. \(\hbox {SrTiO}_{3}\) and \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films grown on Si or Pt have the same phase structure, morphologies and grain size; however, the grain size of the \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films grown on Si is slightly larger than those of the \(\hbox {SrTiO}_{3}\) films grown on Si and the \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films grown on Pt. The \(\hbox {SrTiO}_{3}\) or \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films grown on Si or Pt all exhibit bipolar resistive-switching behaviour and follow the same conductive mechanism; however, the \(\hbox {Ag}/\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}/\hbox {Si}\) device possesses the highest \(R_{\mathrm{HRS}}{/}R_{\mathrm{LRS}}\) of \(10^{5}\) and the best endurance and retention characteristics. The doping of Bi is conducive to enhance the \(R_{\mathrm{HRS}}{/}R_{\mathrm{LRS}}\) of the \(\hbox {SrTiO}_{3}\) films; meanwhile, the Si substrates help improve the endurance and retention characteristics of the \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films.     

Synthesis and Characterization of Nb Substitution on (Bi-Pb)-2223 Superconductors

In this study, samples of \(\hbox {Bi}_{1.65}\hbox {Pb}_{{ 0.35-x}}\hbox {Nb}_{{ x}}\hbox {Sr}_{2}\hbox {Ca}_{2}\hbox {Cu}_{3}\hbox {O}_{10+\delta }\) were prepared by solid-state reaction method and the effect of Nb substitution for Pb on the structural and superconducting properties of this material was investigated. The room-temperature X-ray diffraction patterns indicated that all the samples have the dominant phase of high-\({T}_{\mathrm{c}}\) (Bi-2223). However, other phases such as Bi-2212 and some impurity phases like \(\hbox {SrCu}_{2}\hbox {O}_{2}\), \(\hbox {CuNb}_{2}\hbox {O}_{6}\), \(\hbox {CaCuO}_{3}\) and CuO were also obtained from XRD patterns. An increasing amount of \(\hbox {Nb}^{+5}\) substitutions for \(\hbox {Pb}^{+2}\) led to a phase transition from Bi-2223 to Bi-2212. Electrical resistivity and magnetic measurements revealed that the critical temperature and the critical current density decreases with increasing Nb content due to the enhancement of Bi-2212 phase and appearance of impurities. SEM images indicated that samples porosity changes due to the disrupted grain growth with the substitution of Pb ions with Nb ions.     

Predicting $$\hbox {CO}_{2}$$ Solubility in Imidazole Ionic Liquids for Use in Absorption Refrigeration Systems by Using the Group Contribution Equation of State Method

Traditional absorption refrigeration such as \(\hbox {H}_{2}\hbox {O}\)–LiBr- and \(\hbox {NH}_{3}\)–\(\hbox {H}_{2}\hbox {O}\)-based refrigeration has limited applications because of several issues, including crystallization, corrosion, and large volume. \(\hbox {CO}_{2}\)–ionic liquids (ILs) as new absorption working pairs were investigated in this study. The objective was to use the group contribution equation of state (GC-EOS) method to predict the solubilities of binary systems containing high-pressure \(\hbox {CO}_{2}\)–imidazole bis(trifluoromethanesulfonimide) ILs and to investigate the applicability and accuracy of the GC-EOS model. The results showed that at pressures up to 11.0 MPa and temperatures of 273 K to 400 K, the \(\hbox {CO}_{2}\) solubility in the ILs increased with increasing system pressure but decreased with increasing temperature, and its variation rate was lower at higher pressures or temperatures. Also, \(\hbox {CO}_{2}\) solubility increased in the order of [emim][\(\hbox {Tf}_{2}\hbox {N}\)] < [bmim][\(\hbox {Tf}_{2}\hbox {N}\)] < [hmim][\(\hbox {Tf}_{2}\hbox {N}\)] < [omim][\(\hbox {Tf}_{2}\hbox {N}\)], indicating that longer alkyl chains of identical IL families resulted in higher \(\hbox {CO}_{2 }\) solubility. The model prediction of \(\hbox {CO}_{2}\) solubility in the four different ILs showed reasonable consistency with the corresponding experimental results from the literature; the largest deviation was 5.7 % for \(\hbox {CO}_{2}\)-[emim][\(\hbox {Tf}_{2}\hbox {N}\)]. Therefore, it can be concluded that the GC-EOS model is a promising theoretical solution that can be used to search for suitable \(\hbox {CO}_{2}\)–IL working pairs for absorption refrigeration systems.     

Microwave dielectrics: solid solution,ordering and microwave dielectric properties of $$(1{-}x)\hbox {Ba}(\hbox {Mg}_{1/3}\hbox {Nb}_{2/3})\hbox {O}_{3}{-}x\hbox {Ba(Mg}_{1/8}\hbox {Nb}_{3/4})\hbox {O}_{3}$$ ceramics

The effect of Ba(\(\hbox {Mg}_{1/8}\hbox {Nb}_{3/4})\hbox {O}_{3}\) phase on structure and dielectric properties of \(\hbox {Ba(Mg}_{1/3}\hbox {Nb}_{2/3})\hbox {O}_{3}\) was studied by synthesizing \((1{-}x)\hbox {Ba(Mg}_{1/3}\hbox {Nb}_{2/3})\hbox {O}_{3}{-}x\hbox {Ba}(\hbox {Mg}_{1/8}\hbox {Nb}_{3/4})\hbox {O}_{3}\) (\(x = 0\), 0.005, 0.01 and 0.02) ceramics. Superlattice reflections due to 1:2 ordering appear as low as \(1000^{\circ }\hbox {C}\). \(\hbox {Ba}(\hbox {Mg}_{1/3}\hbox {Nb}_{2/3})\hbox {O}_{3}\) forms solid solution with \(\hbox {Ba}(\hbox {Mg}_{1/8}\hbox {Nb}_{3/4})\hbox {O}_{3}\) for all ‘x’ values studied until \(1350^{\circ }\hbox {C}\). Ordering was confirmed by powder X-ray diffraction pattern, Raman study and HRTEM. Ceramic pucks can be sintered to density \({>}92\%\) of theoretical density. Temperature and frequency-stable dielectric constant and nearly zero dielectric loss (tan \(\delta \)) were observed at low frequencies (20 MHz). The sintered samples exhibit dielectric constant (\(\varepsilon _{\mathrm{r}})\) between 30 and 32, high quality factor between 37000 and 74000 GHz and temperature coefficient of resonant frequency (\(\tau _{\mathrm{f}})\) between 21 and \(24\hbox { ppm }^{\circ }\hbox {C}^{-1}\).     

Effects of electrolyte concentration and current density on the properties of electro-deposited NiFeW alloy coatings

NiWP alloy coatings were prepared by electrodeposition, and the effects of ferrous chloride (\(\hbox {FeCl}_{2})\), sodium tungstate (\(\hbox {Na}_{2}\hbox {WO}_{4})\) and current density (\(D_{\mathrm{K}}\)) on the properties of the coatings were studied. The results show that upon increasing the concentration of \(\hbox {FeCl}_{2}\), initially the Fe content of the coating increased and then tended to be stable; the deposition rate and microhardness of coating decreased when the cathodic current efficiency (\(\eta \)) initially increased and then decreased; and for a \(\hbox {FeCl}_{2}\) concentration of \(3.6\, \hbox {g\,l}^{-1}\), the cathodic current efficiency reached its maximum of 74.23%. Upon increasing the concentration of \(\hbox {Na}_{2}\hbox {WO}_{4}\), the W content and microhardness of the coatings increased; the deposition rate and the cathode current efficiency initially increased and then decreased. The cathodic current efficiency reached the maximum value of 70.33% with a \(\hbox {Na}_{2}\hbox {WO}_{4}\) concentration of 50 g \(\hbox {l}^{-1}\), whereas the deposition rate is maximum at 8.67 \(\upmu \hbox {m}\,\hbox {h}^{-1}\) with a \(\hbox {Na}_{2}\hbox {WO}_{4}\) concentration of \(40\, \hbox {g\,l}^{-1}\). Upon increasing the \(D_{\mathrm{K}}\), the deposition rate, microhardness, Fe and W content of the coatings increased, the cathodic current efficiency increases first increased and then decreased. When \(D_{\mathrm{K}}\) was 4 A dm\(^{-2}\), the current efficiency reached the maximum of 73.64%.     

Structural and physical properties of $$\hbox {Sm}^{3+}$$ doped magnesium zinc sulfophosphate glass

Samarium (\(\hbox {Sm}^{3+})\) doped magnesium zinc sulfophosphate glass system of composition (60–\(x)\hbox {P}_{2}\hbox {O}_{5}\)–20MgO–20ZnSO\(_{4}\)–\(x\hbox {Sm}_{2}\hbox {O}_{3}\) (\(x =\) 0.0, 0.5, 1.0, 1.5 and 2.0 mol%) were synthesized using melt-quenching technique. The structure and physical properties of prepared glass samples were characterized. The X-ray diffraction pattern verified their amorphous nature. The physical properties such as density, refractive index, molar volume, rare earth ion concentration, etc. were calculated. The decrease in the optical bandgap energy with increasing \(\hbox {Sm}_{2}\hbox {O}_{3}\) contents was attributed to the alteration in the glass network structures. Fourier transformed infrared spectra and Raman analyses manifested the depolymerization of \(\hbox {ZnSO}_{4}\) in the phosphate host matrix. The present findings may be beneficial for the advancement of functional glasses.     

Sn-adopted fullerene $$(\hbox {C}_{60})$$ nanocage as acceptable catalyst for silicon monoxide oxidation

In recent years, the discovery of metal catalysts for the oxidation of silicon monoxide (SiO) has become extremely important. In first step, the Sn adoption of fullerene (\(\hbox {C}_{60})\) was investigated and then activation of surface of \(\hbox {Sn-C}_{60}\) via \(\hbox {O}_{2}\) molecule was examined. In second step, the SiO oxidation on surface of \(\hbox {Sn-C}_{60}\) via Langmuir Hinshelwood (LH) and Eley Rideal (ER) mechanisms was investigated. Results show that \(\hbox {O}_{2}\hbox {-Sn-C}_{60}\) can oxidize the SiO molecule via \(\hbox {Sn-C}_{60}\hbox {-O-O}^{*} + \hbox {SiO}\rightarrow \hbox {Sn-C}_{60}\hbox {-O-O}^{*}\hbox {-SiO} \rightarrow \hbox {Sn-C}_{60}\hbox {-O}^{*} + \hbox {SiO}_{2}\) and \(\hbox {Sn-C}_{60}\hbox {-O}^{*} + \hbox {SiO}\rightarrow \hbox {Sn-C}_{60} + \hbox {SiO}_{2}\) reactions. Results show that SiO oxidation via the LH mechanism has lower energy barrier than ER mechanism. Finally, \(\hbox {Sn-C}_{60}\) is an acceptable catalyst with high performance for SiO oxidation in normal temperature.     

Superconducting epitaxial $$\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\delta }$$ on $$\hbox {SrTiO}_{3}$$SrTiO3-buffered Si(001)

Thin films of optimally doped(001)-oriented \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\updelta }\) are epitaxially integrated on silicon(001) through growth on a single crystalline \(\hbox {SrTiO}_{3}\) buffer. The former is grown using pulsed-laser deposition and the latter is grown on Si using oxide molecular beam epitaxy. The single crystal nature of the \(\hbox {SrTiO}_{3}\) buffer enables high quality \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\updelta }\) films exhibiting high transition temperatures to be integrated on Si. For a 30-nm thick \(\hbox {SrTiO}_{3}\) buffer, 50-nm thick \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\updelta }\) films that exhibit a transition temperature of \(\sim \)93 K, and a narrow transition width (<5 K) are achieved. The integration of single crystalline \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\updelta }\) on Si(001) paves the way for the potential exploration of cuprate materials in a variety of applications.     

Synthesis of $$\hbox {Ag}_{2}\hbox {Se}$$–graphene–$$\hbox {TiO}_{2} $$TiO2 nanocomposite and analysis of photocatalytic activity of $$\hbox {CO}_{2}$$CO2 reduction to $$\hbox {CH}_{3}\hbox {OH}$$CH3OH

The present work deals with the development of a new ternary composite, \(\hbox {Ag}_{2}\hbox {Se}\)–\(\hbox {G}\)–\(\hbox {TiO}_{2}\), using ultrasonic techniques as well as X-ray diffraction (XRD), scanning electron microscopy (SEM), high transmission electron microscopy (HTEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and UV–Vis diffuse reflectance spectra (DRS) analyses. The photocatalytic potential of nanocomposites is examined for \(\hbox {CO}_{2}\) reduction to methanol under ultraviolet (UV) and visible light irradiation. \(\hbox {Ag}_{2}\hbox {Se}\)–\(\hbox {TiO}_{2}\) with an optimum loading graphene of 10 wt% exhibited the maximum photoactivity, obtaining a total \(\hbox {CH}_{3}\hbox {OH}\) yield of 3.52 \(\upmu \hbox {mol}\,\hbox {g}^{-1}\,\hbox {h}^{-1}\) after 48 h. This outstanding photoreduction activity is due to the positive synergistic relation between \(\hbox {Ag}_{2}\hbox {Se}\) and graphene components in our heterogeneous system.     

Effect of annealing-temperature-assisted phase evolution on conductivity of solution combustion processed calcium vanadium oxide films

In this work, the effect of annealing temperature on the conductivity of solution-combustion-synthesized calcium vanadium oxide (CVO) films was studied. Conductivity was tailored by the appearance of the phases like \(\hbox {CaVO}_{3}\), \(\hbox {CaV}_{2}\hbox {O}_{5}\) and \(\hbox {Ca}_{2}\hbox {V}_{2}\hbox {O}_{7}\) as a function of annealing temperature; \(\hbox {CaVO}_{3}\) and \(\hbox {CaV}_{2}\hbox {O}_{5}\) are responsible for high conductivity, whereas \(\hbox {V}^{5+}\) presence in \(\hbox {Ca}_{2}\hbox {V}_{2}\hbox {O}_{7}\) contributes towards dielectric nature. Evolution of phases of CVO was identified through X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. A detailed conductivity measurement as a function of annealing temperature helps us to identify the decreasing trend of conductivity with increasing temperature up to \(400{^{\circ }}\hbox {C}\); beyond this it behaves like an insulator. There was a stable conductivity while aging the films in ambient for a few days. This study revealed safe application temperature domain of CVO, and a clear correlation of electrical conductivity with the in-depth structural–compositional–morphological study.     

Rectifying resistance-switching behaviour of Ag/SBTO/STMO/$$\hbox {p}^{+}$$-Si heterostructure films

The \(\hbox {Sr}_{0.88}\hbox {Bi}_{0.12}\hbox {TiO}_{3}/\hbox {SrTi}_{0.92}\hbox {Mg}_{0.08}\hbox {O}_{3}\) (SBTO/STMO) heterostructure films were prepared on \(\hbox {p}^{+}\hbox {-Si}\) substrates by sol–gel spin-coating technique, and the films had good crystallinity and uniform grain distribution. The heterostructure films with a structure of Ag/SBTO/STMO/\(\hbox {p}^{+}\hbox {-Si}\) exhibited a bipolar, remarkable resistance-switching characteristic, and \(R_{\mathrm{HRS}}/R_{\mathrm{LRS}}\,\,{\sim }10^{4}\). More importantly, the heterostructure films showed rectifying characteristic in the low resistance state (LRS), and the rectification ratio can reach \(10^{2 }\) at \(\pm 1\hbox { V}\). The dominant resistive-switching conduction mechanism of high resistance state (HRS) was Ohmic behaviour, and the LRS changed to space charge-limited current (SCLC).     

Structural,dielectric and piezoelectric study of Ca-, Zr-modified $$\hbox {BaTiO}_{3}$$ lead-free ceramics

We prepared a lead-free ceramic (\(\hbox {Ba}_{0.85}\hbox {Ca}_{0.15})(\hbox {Ti}_{1-x}\hbox {Zr}_{x})\hbox {O}_{3}\) (BCTZ) using the conventional mixed oxide technique. The samples were prepared by an ordinary mixing and sintering technique. In this study we investigated how small amounts of \(\hbox {Zr}^{4+}\) can affect the crystal structure and microstructure as well as dielectric and piezoelectric properties of \(\hbox {BaTiO}_{3}\). X-ray diffraction analysis results indicate that no secondary phase is formed in any of the BCTZ powders for \(0 \le x \le 0.1\), suggesting that \(\hbox {Zr}^{4+}\) diffuses into \(\hbox {BaTiO}_{3}\) lattices to form a solid solution. Scanning electron microscopy micrographs revealed that the average grain size gradually increased with \(\hbox {Zr}^{4+}\) content from 9.5 \(\upmu \!\hbox {m}\) for \(x = 0.02\) to 13.5 \(\upmu \!\hbox {m}\) for \(x = 0.1\); Curie temperature decreased due to the small tetragonality caused by \(\hbox {Zr}^{4+}\) addition. Owing to the polymorphic phase transition from orthorhombic to tetragonal phase around room temperature, it was found that the composition \(x = 0.09\) showed improved electrical properties and reached preferred values of \(d_{33} = 148\) pC \(\hbox {N}^{-1}\) and \(K_{\mathrm{p}} = 27\%\).     

Evaluation of the elastic properties of monovalent oxides using $$\hbox {TeO}_{2}$$-based glasses

Quaternary tellurite glasses with composition \(75\hbox {TeO}_{2}\)–\(5\hbox {WO}_{3}\)–\(15\hbox {Nb}_{2} \hbox {O}_{5}\)–\(5\hbox {M}_{x} \hbox {O}_{y}\) in mol%, where \(\hbox {M}_{x}\hbox {O}_{y}\) = (\(\hbox {Na}_{2}\hbox {O}, \, \hbox {Ag}_{2}\hbox {O}\), ZnO, MgO, CuO, NiO, \(\hbox {TiO}_{2}\), \(\hbox {MnO}_{2}\)), were prepared by the normal melt-quenching method. The ultrasonic velocities (longitudinal and shear) were measured in these glasses using the pulse-echo technique at room temperature. Their elastic moduli, microhardness and Debye temperature were calculated and discussed in terms of the modifier’s ionicity and quantitatively in terms of number of bonds per unit volume and the cross-link density. In this study, the values of ultrasonic velocities, elastic moduli, Debye temperature and microhardness were found to be strongly dependent on three factors, namely: (i) modifier’s ionicity; (ii) trigonal pyramid (\(\hbox {TeO}_{3}\))/trigonal bipyramid (\(\hbox {TeO}_{4}\)) ratio; and (iii) glass transition temperature \(T_\mathrm{g}\). We used the Makishima and Mackenzie’s model to calculate the theoretical elastic moduli and to indicate that the experimental values were in good agreement with the theoretical values.