Temperature effects on the electrical characteristics of $$\mathrm{Al}/\mathrm{PTh}-\mathrm{SiO}_{2}/\mathrm{p\hbox {-}Si}$$ structure

The temperature-dependent current–voltage (\(I\text {--}V\)) and capacitance–voltage (\(C\text {--}V\)) characteristics of the fabricated Al/p-Si Schottky diodes with the polythiopene–SiO\(_{2}\) nanocomposite (\(\hbox {PTh--SiO}_{2}\)) interlayer were investigated. The ideality factor of \(\hbox {Al}/\hbox {PTh--SiO}_{2}/{p}\text {-Si}\) Schottky diodes has decreased with increasing temperature and the barrier height has increased with increasing temperature. The change in the barrier height and ideality factor values with temperature was attributed to inhomogeneties of the zero-bias barrier height. Richardson plot has exhibited curved behaviour due to temperature dependence of barrier height. The activation energy and effective Richardson constant were calculated as 0.16 eV and \(1.79 \times 10^{-8} \hbox {A\,cm}^{-2} \,\hbox {K}^{-2}\) from linear part of Richardson plots, respectively. The barrier height values determined from capacitance–voltage–temperature (\(C\text {--}V\text {--}T\)) measurements decrease with increasing temperature on the contrary of barrier height values obtained from \(I\text {--}V\text {--}T\) measurements.     

Temperature dependence of characteristic parameters of the Au/C<Subscript>20</Subscript>H<Subscript>12</Subscript>/n-Si Schottky barrier diodes (SBDs) in the wide temperature range

Au/C₂₀H₁₂/n-Si SBD was fabricated and its characteristic parameters such as reverse-saturation current (I_o), ideality factor (n), zero-bias barrier height (Φ_bo), series and shunt resistances (R_s, R_sh) were found as 1.974 × 10^?7 A, 6.434, 0.351 eV, 30.22 Ω and 18.96 kΩ at 160 K and 1.061 × 10^?6 A, 2.34, 0.836 eV, 5.82 Ω and 24.52 kΩ at 380 K, respectively. While the value of n decreases with increasing temperature, Φ_bo increases. The change in Φ_bo with temperature is not agreement with negative temperature coefficient of forbidden band-gap of semiconductor (Si). Thus, Φ _bo versus n, Φ _bo and (n^?1 ? 1) versus q/2kT plots were drawn to obtain an evidence of a Gaussian distribution (GD) of the BHs and all of them have a straight line. The mean value of BH (\( \overline{\varPhi }_{bo} \)) was found as 0.983 eV from the intercept of Φ _bo versus n plot (for n = 1). Also, the value of \( \overline{\varPhi }_{bo} \) and standard deviation (σ_s) were found as 1.123 eV and 0.151 V from the slope and intercept of Φ_bo versus q/2kT plot. By using the modified Richardson plot, the \( \overline{\varPhi }_{bo} \) and Richardson constant (A*) values were obtained as 1.116 eV and 113.44 A cm^?2 K^?2 from the slope and intercept of this plot, respectively. It is clear that this value of A* (=113.44 A cm^?2 K^?2) is very close to their theoretical value of 112 A cm^?2 K^?2 for n-Si. In addition, the energy density distribution profile of surface states (D_it) was obtained from the forward bias I–V data by taking into account the bias dependent of the effective barrier height (Φ _e ) and ideality factor n(V) for four different temperatures (160, 200, 300, and 380 K). In conclusion, the I–V–T measurements of the Au/C₂₀H₁₂/n-Si SBD in the whole temperature range can be successfully explained on the basis of thermionic emission (TE) theory with GD of the BHs.     

Temperature-dependent <Emphasis Type="Italic">C-V</Emphasis> characteristics of Au/ZnO/n-Si device obtained by atomic layer deposition technique

Since the importance of Schottkky devices, Au/ZnO/n-Si device were obtained, and the capacitance–voltage (C-V) and conductance-voltage (G-V) characteristics of Au/ZnO/n-Si device were studied using admittance spectroscopy at changing temperature from 160 to 340 K with 20 K intervals and ?1 to +2 V bias voltage range. The interface thin film ZnO layer was deposited on the n-type Si wafer by atomic layer deposition technique (ALD) in order to obtain homogenous interface layer. The layer thickness of ZnO was taken as 10 nm by the resulting ZnO film growth rate at about 1.45 Å per cycle. This thin film layer was characterized with XRD and AFM analyses. It can be seen from the C-V curves of the device that the capacitance values increased in depletion region with increasing temperature and exhibited peaks towards to forward biases after 240 K temperature. The changing of capacitance values confirmed re-ordering and re-structuring of charges in the interface of the device with changing temperature. The G-V curves of the device also increased with increasing temperature and towards to forward bias voltages due to increasing free charges in the interface. The series resistance (\({R}_{s}\)) of the device was taken into account to understand its effect on main electrical parameters, and it could be seen from these results that the \({R}_{s}\) strongly depends on the device temperature. The impedance (Z) values decreased with changing from ?1 to +2 V bias voltages and increasing temperature. The barrier height which was obtained from the C ^?2 -V plots increased a slope of 0.00108 eV/K with a decrease in temperature from 160 to 340 K. It can be concluded that the Au/ZnO/n-Si device may be used and improved for next technological applications such as capacitor and memristor.     

Understanding of post deposition annealing and substrate temperature effects on structural and electrical properties of Gd<Subscript>2</Subscript>O<Subscript>3</Subscript> MOS capacitor

The purpose of this study is to understand the effects of substrate temperature (ST) and post deposition annealing (PDA) on the structural-electrical properties of Gd₂O₃ film and to evaluate the electrical performances of the MOS based devices formed with this dielectric. The Gd₂O₃/Si structures were annealed at 500, 600, 700, and 800 °C under N₂ ambient after the films were grown on heated p-Si substrate at various temperatures ranged from 20 to 300 °C by RF magnetron sputtering. For any given ST, the crystallization/grain size increased with increasing PDA temperature. The bump in the accumulation region or continuous decrease in the capacitance values of the inversion region of the C–V curves for 800 °C PDA was not observed. The lowest effective oxide charge density (Q _eff ) value was obtained to be ??1.13?×?10¹¹ cm^?2 from the MOS capacitor with Gd₂O₃, which is grown on heated Si at 300 °C and annealed at 800 °C. The density of the interface states (D _it ) was found to be in the range of 0.84?×?10¹¹ to 1.50?×?10¹¹ eV^?1 cm^?2. The highest dielectric constant (ε) and barrier height \(({\Phi _B})\) values were found to be 14.46 and 3.68, which are obtained for 20 °C ST and 800 °C PDA. The results show that the negative charge trapping in the oxide layer is generally more than that of the positive, but, it is reverse of this situation at the interface. The leakage current density decreased after 20 °C ST, but no significant change was observed for other ST values.     

Single Gaussian distribution of barrier height in Al/PS–ZnPc/p-Si type Schottky barrier diode in temperature range of 120–320 K

Possible current-transport mechanism in aluminum/polystrene–zincphthalocyanine/ptype silicon Schotky barrier diode (Al/PS–ZnPc/p-Si; SBD), for the forward bias current–voltage (I–V) characteristics were carried out in the temperature range of 120–320 K. The high value of ideality factor (n), especially at low temperatures, was attributed to the existence of PS layer, barrier in-homogeneities and particular density distribution of surface states between metal and semiconductor. An abnormal decrease in the zero-bias barrier height (BH) and increase in n with decreasing temperature which leads to non-linearity in the Richardson plot, have been observed. Linear relationship between BH and n was also observed. BH was plotted as a function of q/2kT to obtain evidence of Gaussian distribution (GD) of the BHs. The mean BH and its standard deviation (σ) were obtained as 1.03 eV and 0.117 V from the slope and intercept of this plot, respectively. Thus, the modified ln(Io/T²) ? q²σo²/2k²T² versus q/kT plot gives mean BH and the modified Richardson constant \({\text{A}}_{\bmod }^{*}\) as 1.043 eV and 29.824 A cm^?2 K^?2, respectively. This value of the Richardson constant is very close to the theoretical value of 32 A cm^?2 K^?2 for p-type Si. Therefore, non-ideal behavior of forward-bias I–V characteristics in Al/PS–ZnPc/p-Si might be successfully explained in terms of the thermionic emission mechanism with single GD of BHs.     

Experimental Study of the Thermodynamic Properties of Diethyl Ether (DEE) at Saturation

The isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\), saturation densities (\({\rho _{\rm S}^{\prime}}\) and \(({\rho_{\rm S}^{\prime\prime})}\)), vapor pressures (P _S), thermal-pressure coefficients \({\gamma_V=\left({\partial P/\partial T}\right)_V}\), and first temperature derivatives of the vapor pressure γ _S = (dP _S/dT) of diethyl ether (DEE) on the liquid–gas coexistence curve near the critical point have been measured with a high-temperature and high-pressure nearly constant-volume adiabatic piezo-calorimeter. The measurements of \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) were made in the liquid and vapor one- and two-phase regions along the coexistence curve. The calorimeter was additionally supplied with a calibrated extensometer to accurately and simultaneously measure the PVT, C _V VT, and thermal-pressure coefficient, γ _V , along the saturation curve. The measurements were carried out in the temperature range from 416 K to 466.845 K (the critical temperature) for 17 liquid and vapor densities from 212.6 kg · m^?3 to 534.6 kg · m^?3. The quasi-static thermo- (reading of PRT, T ? τ plot) and baro-gram (readings of the tensotransducer, P ? τ plot) techniques were used to accurately measure the phase-transition parameters (P _S ,ρ _S ,T _S) and γ _V . The total experimental uncertainty of density (ρ _S), pressure (P _S), temperature (T _S), isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\), and thermal-pressure coefficient, γ _V , were estimated to be 0.02 % to 0.05 %, 0.05 %, 15 mK, 2 % to 3 %, and 0.12 % to 1.5 %, respectively. The measured values of saturated caloric \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) and saturated thermal (P _S, ρ _S, T _S) properties were used to calculate other derived thermodynamic properties C _P , C _S, W, K _T , P _int, ΔH _vap, and \({\left({\partial V/\partial T}\right)_P^{\prime}}\) of DEE near the critical point. The second temperature derivatives of the vapor pressure, (d² P _S/dT ²), and chemical potential, (d² μ/dT ²), were also calculated directly from the measured one- and two-phase liquid and vapor isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) near the critical point. The derived values of (d² P _S/dT ²) from calorimetric measurements were compared with values calculated from vapor–pressure equations. The measured and derived thermodynamic properties of DEE near the critical point were interpreted in terms of the “complete scaling” theory of critical phenomena. In particular, the effect of a Yang–Yang anomaly of strength R _μ on the coexistence-curve diameter behavior near the critical point was studied. Extended scaling-type equations for the measured properties P _S (T), ρ _S (T), and \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) as a function of temperature were developed.     

Barrier inhomogeneities in titanium Schottky contacts formed on argon plasma etched p-type Si0.95Ge0.05

Electrical properties of Ti Schottky barrier diode fabricated on argon plasma etched p-type Si_0.95Ge_0.05 were studied using current–voltage (I–V) over a wide temperature range (100–300 K). The transport properties of the junction were analyzed by investigating the temperature dependence of both the effective Schottky barrier height (Φ _0bp) and the ideality factor (n). It is shown that the ideality factor increases and the Schottky barrier height (SBH) decreases with decreasing temperature. This abnormal temperature dependence of the Φ _0bp and n is explained on the basis of a thermionic emission conduction mechanism with Gaussian distributed barrier heights due to the barrier height inhomogeneities at the metal-p-Si_0.95Ge_0.05 interface. From the linear plot of the experimental SBH versus 1/T, a homogeneous SBH ( $\overline{\varPhi }_{0bp}$ ) and a zero-bias standard deviation (σ_0s) values of approximately 0.55 eV and 67 mV, respectively were computed. Furthermore the modified Richardson plot according to the Gaussian distribution model resulted in a homogeneous SBH ( $\overline{\varPhi }_{0bp}$ ) and a Richardson constant (A*) of 0.55 eV and 35 A/cm² K², respectively. The A* value obtained from this plot is in very close agreement with the theoretical value of 32 A/cm² K² for p-type Si_0.95Ge_0.05. Furthermore, the SBH is found to decrease linearly as the interface states density (N _ss) increases. It is proposed that the lateral inhomogeneities of the SBH are actually attributed to the distribution of the interface states which are in turns resulting from the plasma etching induced defects beneath the Si_0.95Ge_0.05 surface.     

Temperature dependence of the lowest-direct-bandgap energy in the ternary chalcopyrite semiconductor AgInSe<Subscript>2</Subscript>

Photoreflectance spectra have been measured on the ternary chalcopyrite semiconductor AgInSe₂ at T = 15–300 K. The direct-bandgap energies, E _0A, E _0B, and E _0C, of AgInSe₂ show unusual temperature dependence at low temperatures. The resultant temperature coefficients \({\partial E_{0\alpha}/\partial T}\) \(({\alpha=\hbox{A, B, C}})\) are positive at T below ～100 K and negative above ～100 K. These results are successfully explained by taking into account the negative lattice thermal expansion at low temperatures. The spin–orbit and crystal-field parameters Δ_so and Δ_cf are also found to show small temperature variations.     

Numerical and experimental verification of a damping model used in DEM

This paper presents a study on the damping ratio \(({\upbeta })\) used in discrete element simulations. Physical experiments are performed by dropping particles from a predetermined height. Two kinds of granular particles, aluminum and steel spheres, are used. The size of these particles are the same. The process of particle depositing under gravity is simulated using the discrete element method. The experimental observation is compared with the numerical result to identify the appropriate \({\upbeta }\). The result indicates that the appropriate damping ratio used in discrete element simulations is between 0.2 and 0.3 %. Various \({\upbeta }\) are then used in the numerical simulations to study the effect of \({\upbeta }\) on the dropping process. The final height of the sample relates to \({\upbeta }\) and the drop height. The effect of \({\upbeta }\) is more profound for small drop height. For greater drop height, the effect of \({\upbeta }\) is negligible.     

Investigation of capacitance characteristics in metal/high-<Emphasis Type="Italic">k</Emphasis> semiconductor devices at different parameters and with and without interface state density (traps)

Capacitance vs. voltage (\(C{-}V\)) curves at AC high frequency of a metal–insulator–semiconductor (MIS) capacitor are investigated in this paper. Bi-dimensional simulations with Silvaco TCAD were carried out to study the effect of oxide thickness, the surface of the structure, frequency, temperature and fixed charge in the oxide on the \(C{-}V\) curves. We evaluate also the analysis of MIS capacitor structures by different substrate doping concentrations with and without interface state density at different temperatures (100, 300 and 600 K). These studies indicate that the doping substrate concentration and the traps enormously affect the high-frequency \(C{-}V\) curve behaviour. We also demonstrate that for low and high temperatures, the high-frequency \(C{-}V\) curves behaviour changes, indicating that the capacitance due to the substrate is significantly influenced in these conditions (bias and substrate doping concentration).     

Influence of Helium Atoms Absorption on the Emission Properties of Carbon Nanotubes

We investigated the emission properties of charge sources based on carbon nanotubes prepared by arc discharge deposition of nanotubes onto a flat copper substrate (Borisenko et al. in Instrum Exp Tech 57(6):755, 2014; Low Temp Phys 41(7):567, 2015). The charge sources were submerged into superfluid helium at temperature \(T=1.3\) K. The collector fixed above the charge source at a distance of 0.3 mm was connected to an electrometer. The current of charges was measured by the electrometer when a high voltage was applied to the charge source. In the originally prepared source, the emission of charges (electrons) on the level of \(10^{-10}\hbox {A}\) is observed at a negative voltage above \(U=80\) V and increases with increasing voltage. If the source of charge was kept in liquid helium for 15 h, the current–voltage characteristic changed significantly. The current of charges on the same level of \(10^{-10}\) A was registered at a voltage of \(U=150\) V. Extraction of gases from the source placed in a vacuum chamber at room temperature for 48 h leads to the complete recovery of the emission properties. One can assume that the degradation of the emission properties of the sources is associated with the adsorption of helium atoms by carbon nanotubes at low temperatures. We did not observe any degradation of the emission properties of the charge sources in the case of positive charges injection into superfluid helium.     

New NTC thermistors based on LaCrO<Subscript>3</Subscript>–Mg(Al<Subscript>0.7</Subscript>Cr<Subscript>0.3</Subscript>)<Subscript>2</Subscript>O<Subscript>4</Subscript> composite ceramics

In this study, the xLaCrO₃–(1?x)Mg(Al_0.7Cr_0.3)₂O₄ (x?=?0.1, 0.2, 0.3, 0.4) negative temperature coefficient composite ceramics were fabricated through conventional solid state reaction at 1650?°C. X-ray diffraction analysis has revealed that the sintered ceramics are consisted of cubic spinel Mg(Al_0.7Cr_0.3)₂O₄ phase and orthorhombic perovskite LaCrO₃ phase. The obtained values of \({{\rho }_{\text{300}}}\) and \({{B}_{400/800}}\) and \({{E}_{\text{a}}}\) are in the range of 1.55?×?10²–1.41?×?10⁸ Ωcm, 756–11317 K, 0.065–0.976 eV, respectively. The electrical properties of these ceramics can be adjusted by the LaCrO₃ contents. Such ceramics could be suitable for high temperature NTC thermistor application.     

Biocorrosion and biodegradation behavior of ultralight Mg–4Li–1Ca (LC41) alloy in simulated body fluid for degradable implant applications

Biocorrosion and biodegradation behavior of Mg–4Li–1Ca alloy were investigated for industrially important end product conditions, namely the homogenized, rolled, and rolled + annealed ones. Among the three, homogenized material showed the highest corrosion rate (27.2 mm/year) in a simulated body fluid (SBF) owing to its coarse grain structure containing long dumbbell-shaped eutectic phase. Rolled + annealed material exhibited the lowest corrosion rate (0.94 mm/year) corresponding to the highest corrosion resistance (1.854 kΩ cm²) in SBF. This higher corrosion resistance is associated with a uniform distribution of corrosion sites and a lower occurrence of twins in the microstructure. However, the rolled material showed a greater corrosion rate due to an appreciable volume fraction of {10\( \bar{1} \)1} compression twins, {10\( \bar{1} \)2} tension twins, and {10\( \bar{1} \)1}–{10\( \bar{1} \)2} double twins, which form galvanic couples with the adjacent grains that enhances localized corrosion. A mechanism of biodegradation at the alloy/SBF interface is proposed. It involves the formation of bone-like hydroxyapatite and metastable octa calcium phosphate, along with other degradation products, such as magnesium hydroxide and lithium hydroxide.     

Electrical and Thermal Characteristics of the Insulator–Metal Transition in Crystalline $$\hbox {V}_{2}\hbox {O}_{5}$$ Films

The electrical and thermal properties with respect to the crystallization in \(\hbox {V}_{2}\hbox {O}_{5}\) thin films were investigated by measuring the resistance at different temperatures and applied voltages. The changes in the crystal structure of the films at different temperatures were also explored using Raman measurements. The thermal diffusivity of the crystalline \(\hbox {V}_{2}\hbox {O}_{5}\) film was measured by the nanosecond thermoreflectance method. The microstructures of amorphous and crystalline \(\hbox {V}_{2}\hbox {O}_{5}\) were observed by SEM and XRD measurements. The temperature-dependent Raman spectra revealed that a structural phase transition does not occur in the crystalline film. The resistance measurements of an amorphous film indicated semiconducting behavior, whereas the resistance of the crystalline film revealed a substantial change near \(250\,{^{\circ }}\hbox {C}\), and Ohmic behavior was observed above \(380\,{^{\circ }}\hbox {C}\). This result was due to the metal–insulator transition induced by lattice distortion in the crystalline film, for which \(T_{\mathrm{c}}\) was \(260\,{^{\circ }}\hbox {C}\). \(T_{\mathrm{c}}\) of the film decreased from 260 \({^{\circ }}\hbox {C}\) to \(230\,{^{\circ }}\hbox {C}\) with increasing applied voltage from 0 V to 10 V. Furthermore, the thermal diffusivity of the crystalline film was \(1.67\times 10^{-7}\,\hbox {m}^{2}\cdot \hbox {s}^{-1}\) according to the nanosecond thermoreflectance measurements.     

Crystal structure,thermal behaviour,vibrational spectroscopy and optical properties of new compounds K$$_{}$$Ca(HAsO$$_{4}$$4)$$_{}\cdot $$·H$$_{}$$O with kröhnkite-type chain

The new kröhnkite compound called potassium calcium-bis-hydrogen arsenate dihydrate K\(_{2}\)Ca(HAsO\(_{4})_{2}\cdot \)2H\(_{2}\)O was obtained by hydrothermal method and characterized by X-ray diffraction, infrared spectroscopy, Raman scattering, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis and optical (photoluminescence and absorption) properties. It crystallizes in the triclinic space group P\(\bar{1}\) and unit cell parameters \(a = 5.971(3)\) Å, \(b =6.634(3)\) Å, \(c = 7.856(4)\) Å, \(\alpha =104.532(9)\) \(^{\circ }\), \(\beta = 105.464(9)\) \(^{\circ }\) and \(\gamma = 109.698(9)\) \(^{\circ }\). The structure of K\(_{2}\)Ca(HAsO\(_{4})_{2}\cdot \)2H\(_{2}\)O built up from this infinite, (Ca(HAsO\(_{4})_{2}\)(H\(_{2}\)O)\(_{2})^{2+}\), was oriented along an axis resulting from the association of CaO\(_{6}\) octahedra alternating with each two HAsO\(_{4}\) tetrahedra by sharing corners. Each potassium atom links two adjacent chains by three oxygen atoms of HAsO\(_{4}\) tetrahedra. TGA and DSC have shown the absence of phase transition. The existence of vibrational modes corresponding to the kröhnkite is identified by the IR and Raman spectroscopies in the frequency ranges of 400–4000 and 20–4000 cm\(^{-1}\), respectively. The photoluminescence measurement show one peak at 507 nm, which is attributed to band–band (free electron–hole transitions) and (bound electron–hole transitions) emissions within the AsO\(_{4}\) inorganic part.     

Stability Evaluation and Calibration of Type C Thermocouples at the Pt–C Eutectic Fixed Point

Tungsten–rhenium thermocouples (type C thermocouples) are used to measure temperatures higher than 1500 \({^{\circ }}\)C under protective, inert, or vacuum conditions in a wide range of industries, such as metallurgy, power generation, and aerospace. Generally, the measurement uncertainty of a new tungsten–rhenium thermocouple is about 1 % (20 \({^{\circ }}\)C at 2000 \({^{\circ }}\)C), and a significant drift is always observed above 1200 \({^{\circ }}\)C. Recently, the National Institute of Metrology, China, has spent great efforts to calibrate tungsten–rhenium thermocouples with high-temperature fixed points of up to 2000 \({^{\circ }}\)C. In the present work, three tungsten–rhenium thermocouples made by two manufacturers were calibrated at the Pt–C eutectic fixed point (1738 \({^{\circ }}\)C) and their stability was investigated. A linear fitting and extrapolation method was developed to determine the melting and freezing temperatures of the Pt–C eutectic fixed point for avoiding the effect of thermal resistance caused by the sheath and protection tube. The results show that the repeatability of the calibration is better than 0.9 \({^{\circ }}\)C from the melting curve of the Pt–C fixed point and better than 1.2 \({^{\circ }}\)C from the freezing curve of the Pt–C fixed point, and a good agreement was obtained for the calibration with the melting and freezing temperature plateau through the linear fitting and extrapolation method. The calibration uncertainty of the thermocouples at the Pt–C eutectic fixed point was 3.1 \({^{\circ }}\)C (k \(=\) 2).     

Measurement of the Nonlinearity of Heat-Flux Sensors Employing a $$\hbox {CO}_2$$ laser

Heat-flux sensors are widely used in industry to test building products and designs for resistance to bushfire, to test the flammability of textiles and in numerous applications such as concentrated solar collectors. In Australia, such detectors are currently calibrated by the National Measurement Institute Australia (NMIA) at low flux levels of 20 W \(\cdot \) m\(^{-2}\). Estimates of the uncertainty arising from nonlinearity at industrial levels (e.g. 50 kW \(\cdot \) m\(^{-2}\) for bushfire testing) rely on literature information. NMIA has developed a facility to characterize the linearity response of these heat-flux sensors up to 110 kW \(\cdot \) m\(^{-2}\) using a low-power \(\hbox {CO}_2\) laser and a chopped quartz tungsten–halogen lamp. The facility was validated by comparison with the conventional flux-addition method, and used to characterize several Schmidt–Boelter-type sensors. A significant nonlinear response was found, ranging from (\(3.2 \pm 0.9\))% at 40 kW \(\cdot \) m\(^{-2}\) to more than 8 % at 100 kW \(\cdot \) m\(^{-2}\). Additional measurements confirm that this is not attributable to convection effects, but due to the temperature dependence of the sensor’s responsivity.     

<10$$ \bar{1} $$0> Dislocation at a {2$$ \bar{1} $$$$ \bar{1} $$0} low-angle grain boundary in LiNbO3

A LiNbO₃ bicrystal that contains a {2\( \bar{1} \) \( \bar{1} \)0} low-angle grain boundary with both of 2° tilt misorientation and a slight twist misorientation was fabricated, and resulting dislocation structure at the boundary was analyzed by using transmission electron microscopy (TEM) and scanning TEM. The observations revealed that two types of dislocations of b = 1/3 <2\( \bar{1} \) \( \bar{1} \)0> and b = <10\( \bar{1} \)0> are formed at the boundary. A 1/3 <2\( \bar{1} \) \( \bar{1} \)0> dislocation, which dissociates into two partial dislocations with a {2\( \bar{1} \) \( \bar{1} \)0} stacking fault in between, compensates only tilt misorientation of the boundary. On the other hand, it was found that a <10\( \bar{1} \)0> dislocation, which dissociates into three equivalent partial dislocations with b = 1/3 <10\( \bar{1} \)0>, has both edge and screw components in total. That is, the <10\( \bar{1} \)0> dislocations are formed to compensate the twist misorientation of the boundary, in addition to the tilt misorientation. It is interesting that the three partial dislocations from a <10\( \bar{1} \)0> dislocation are arranged in a zigzag pattern with left–right asymmetry. This special configuration is suggested to originate from the presence of stable stacking fault structure on the {2\( \bar{1} \) \( \bar{1} \)3} plane in LiNbO₃.     

Evolution of magnetic structure of Dy(Co<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ni<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>2</Subscript>B<Subscript>2</Subscript>C

DyNi\(_{2}\)B\(_{2}\)C superconducts at \(T_{c} \approx 6\,{\text{K}}\) and orders antiferromagnetically at \(T_{N}\approx 10\,{\text{K}}.\) Its non-superconducting isomorph DyCo\(_{2}\)B\(_{2}\)C is a ferromagnet with \(T_{C}\approx 6\,{\text{K}}.\) With the aim of mapping out the magnetic properties, in particular magnetic structures, of their solid solutions, we synthesized \(^{11}\)B-enriched Dy(Co\(_{x}\)Ni\(_{1-x}\))\(_{2}\)B\(_{2}\)C (\(x=0.2,0.4,0.6,0.8\)). We investigated the evolution of their magnetic, thermal and transport properties by means of the magnetization, resistivity, specific heat and neutron diffraction techniques. Their crystal structures were confirmed to be ThCr\(_{2}\)-Si\(_{2}\)-type tetragonal (I4/mmm) phase. The magnetic structure was found to be antiferromagnetic with k_0.2 = (0, 0, 1) for x = 0.2; helicoidal with k\(_{0.4}\) = (0, 0, 0.49) and k\(_{0.6}\) = (0, 0, 0.46) for, respectively, x = 0.4 and 0.6 and ferromagnetic with k\(_{0.8}\) = (0, 0, 0) for x = 0.8. We discuss the evolution of such magnetic modes assuming a scenario of an idealized one-dimensional chain of transverse magnetic moments.     

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.