Temperature Coefficient Research Articles

Synthesis and Characterization of the Microwave Dielectric Properties of a (1-x) Li<sub>3</sub>MgNbO<sub>5</sub>–(x) Sr<sub>3</sub>V<sub>2</sub>O<sub>8</sub> Composite for Antenna Application

This study investigates the fabrication of a cylindrical dielectric resonator antenna (CDRA) using ceramic microwave dielectric composites as a resonator. The composites (1-x) Li3MgNbO5-(x) Sr3V2O8 (x=0.25-0.40) have been synthesized via the conventional solid-state reaction method, incorporating 1% B2O3 to lower the sintering temperature. The 0.70-0.30 composite exhibited optimal microwave dielectric properties with a dielectric constant (εr) of 19.20, a quality factor (Q x f) of 3738 GHz, and a temperature coefficient (τf)of -43 ppm/°C. These characteristics render the 0.70-0.30 composite suitable for CDRA applications. The experimentally obtained microwave dielectric parameters were used to simulate the CDRA design using the High-Frequency Structure Simulator design software. A single-feed cylindrical antenna has been fabricated using this composite material as a resonator with a radius × height of 5×6 mm2, mounted on an FR4 substrate measuring close to 25×25×1.6 mm3 and Cu strip as a feed line. The simulated and experimentally measured parameters, including S11, voltage standing wave ratio, and radiation pattern, demonstrated excellent agreement, validating the composite's efficacy for antenna design.

Wear Study on Various Conditions of AA7075 Metal Matrix Composite with Silicon Carbide (SiC), Boron Carbide (B4C) as Reinforcement for Aerospace Applications

This study aims to investigate the wear behavior of AA7075 alloy with the reinforcement of Silicon carbide (SiC) and Boron carbide (B4C) particles. Process parameters are crucial for component quality improvement, particularly in metal matrix composites (MMCs), a unique class of materials used in a variety of technical applications, such as but not limited to automobiles, marine, and aeronautics.These are frequently utilized in challenging applications due to their significantly better strength to weight ratios, stiffness, and then standard materials. However, it has numerous disadvantages, including high weight ratios, high deformation and stresses, poor fatigue life cycle, early wear and friction, and so on. Up till now, numerous reinforcements have been employed to address these crucial problems. Due to its superior properties, aluminum matrix composites (AMCs) have been used in many different applications. This work attempts to examine the wear behavior of AA7075 alloy reinforced with silicon (SiC) and boron (B4C) particles utilizing the stir casting process AA 7075-(SiC)-(B4C) composites were produced by employing AA 7075 as the matrix material with silicon carbide (SiC) and boron carbide (B4C) particles as reinforcement in various percentages of weight (5%, 10%, and 15%). Parameters of the composites, including wear behavior, coefficient of friction, frictional force, and pin temperature were assessed through graphical representation.

Core design and neutronics analysis of lead liquid metal-based heat pipe cooled reactor for undersea purpose

Abstract Various heat pipe-cooled reactors have been conceptualized and designed in recent years, ranging from kilowatts to megawatts, suitable for remote and extreme environments. However, existing designs employ monolith cores, which are saddled with heat transfer deteriorations due to thermal expansion and subsequent deformations are some of the key challenges facing monolith heat pipe reactors. Addressing this, a novel 300 kW heat pipe has been designed by introducing lead liquid instead of the monolith. A comprehensive Monte Carlo neutronics analysis of the designed core has been conducted including its thermal analysis. The core design comes with the following parameters: fresh core excess reactivity of 2.9914 $ that can support a 10-year life cycle, and a negative temperature coefficient of −0.1648 pcm/K. The axial and radial peak power factors at critical states were calculated to be 1.67 and 1.35 respectively. Preliminary thermal hydraulics analysis shows maximum temperatures of 1044 K under normal operation and worst-case accident scenarios (3 heat-pipe failures) of 1,149.9 K. These temperatures are lower than the melting point of uranium nitride fuel and lower than the possible heat pipe boiling failure limit at 1,300 K. Thus, the possibility of fuel melting/heat pipe boiling accidents is avoided. A hypothetical criticality accident was simulated, assuming the core was flooded with water, leading to an increased fission rate. However, the implementation of three emergency rods in the core ensures the subcritical of the reactor.

Halometallate Ionic Liquid Dynamically Regulates Zwitterionic Hydrogels by Synergistic Multiple‐Bond Networks

AbstractImproving the compatibility between high concentration metallic ions and zwitterions to controllable construction of coordination bonds is critical and extremely challenging. Here, a facile and effective strategy to fabricate multifunctional hydrogels by randomly copolymerizing halometallate ionic liquids (ILs) and zwitterions through electron beam irradiation is reported. Introducing metal ions into ILs can balance charges and establish moderate and stable cross‐linked networks with zwitterions. The synergistic effect of coordination bonds and multiple interactions with varying strengths endows hydrogel with outstanding stretchability, compressive strength, rapid response, advanced self‐healing ability, and excellent frost resistance. The multifunctional sensor assembled from hydrogels can timely, accurately, and stably monitor human movement, write anti‐counterfeiting and remotely transmit Morse code signals. Multiple hydrogel sensors are also assembled into a flexible sensor array to track the tactile trajectory and detect spatial distribution of force. Moreover, the obtained hydrogel displays high temperature sensitivity with resistance temperature coefficient of −3.85% °C−1 at 25–40 °C, which can detect tiny temperature changes (0.1 °C). Interestingly, the processed hydrogel can effectively modulate the transmissivity through salt triggering to achieve patterning. Considering the structural designability of halometallate ILs, this work provides new insights for the development of multifunctional hydrogels.

Low temperature catalytic growth graphene with V2O5 prepared with the oxidation method and its application in optoelectronic devices

Based on our previous research on the phase transition property of non-metallic vanadium oxide for low-temperature catalytic growth of graphene, we further propose that V thin films can be deposited by sputtering and then V2O5 thin films can be prepared by oxidizing the V thin films at 400 °C in a rapid annealing furnace with oxygen, which has a better crystalline structure and surface than the V2O5 thin films directly deposited by sputtering. The V2O5 prepared by oxidation was used to catalyze the growth of graphene at 300 °C in a PECVD furnace. During the growth process, a 10-fold increase in the H2 flow rate (200 sccm) was used to repair and eliminate the suspension bonds and defects of graphene, and the quality of graphene films was improved. Due to the high resistivity of V2O5 at room temperature, V2O5 can be directly used as the interlayer of the device, and the graphene-V2O5-Si (GVS) structure photodetector is proposed, which avoids the damage and impact of the transfer process and catalytic layer removal process in the conventional graphene device process. Additionally, because of the negative temperature coefficient of resistance (TCR) of vanadium oxide materials, the optical response of the GVS device is further extended to 1550 nm.

Comparative Study of Different Machine Learning Models for Heat Transfer Performance Prediction of Evaporators in Modular Refrigerated Display Cabinets

This study explores the potential of machine learning models to predict evaporator heat transfer performance in Modular Refrigerated Display Cases (MRDCs). Six experimental datasets from MRDC systems were analyzed to compare the efficacy of six machine learning models: Linear Regression, Decision Tree Regression, Support Vector Machines (SVMs), Feedforward Neural Networks (FNNs), Random Forest (RF), and Light Gradient Boosting Machine (LightGBM). The findings indicate that the ensemble tree-based models, LightGBM and RF, are particularly effective in predicting evaporator heat transfer performance. These models demonstrate high accuracy and robustness, effectively capturing the nonlinear relationship between the evaporator temperature and heat transfer coefficient. Moreover, LightGBM and RF exhibit notable stability and adaptability in scenarios of limited data availability and elevated noise levels. Their consistent predictive accuracy across different experimental conditions highlights their suitability for complex refrigeration systems. This research provides essential insights for optimizing MRDC evaporator performance, establishing a theoretical and data-driven foundation for energy-efficient enhancements and intelligent management within cold chain systems.

Using temperature coefficients to support resonance assignment of intrinsically disordered proteins.

The resonance assignment of large intrinsically disordered proteins (IDPs) is difficult due to the low dispersion of chemical shifts (CSs). Luckily, CSs are often specific for certain residue types, which makes the task easier. Our recent work showed that the CS-based spin-system classification can be improved by applying a linear discriminant analysis (LDA). In this paper, we extend a set of classification parameters by adding temperature coefficients (TCs), i.e., rates of change of chemical shifts with temperature. As demonstrated previously by other groups, the TCs in IDPs depend on a residue type, although the relation is often too complex to be predicted theoretically. Thus, we propose an approach based on experimental data; CSs and TCs values of residues assigned using conventional methods serve as a training set for LDA, which then classifies the remaining resonances. The method is demonstrated on a large fragment (1-239) of highly disordered protein Tau. We noticed that adding TCs to sets of chemical shifts significantly improves the recognition efficiency. For example, it allows distinguishing between lysine and glutamic acid, as well as valine and isoleucine residues based on , N, and C data. Moreover, adding TCs to CSs of , N, , and C is more beneficial than adding CSs. Our program for LDA analysis is available at https://github.com/gugumatz/LDA-Temp-Coeff .

Implied J-V Curves Recorded at Elevated Temperatures Using Light Controlled Heating

The carrier lifetime characterization of solar cells is typically performed at room temperature, although the operational temperature of a solar panels can reach 60 °C. We realized a setup for laser controlled photoconductance decay (PCD) measurement at elevated temperatures induced by light. We investigated precursor p-PERC cells from multiple parts of the same ingot using this technique. From the injection level dependent carrier lifetime results the implied current-voltage characteristics are evaluated as well. We observed a relatively small but noticeable increase of the carrier lifetime up to 30% with increasing the temperature from 30°C to 60°C in all samples. Saturation current values obtained using the Kane-Swanson method indicate, that not only the bulk lifetime improves but the surface recombination rate weakens. Temperature coefficient values of the implied cell efficiency are around -0.35 rel%/°C and slightly below which agrees with typical results of electrical tests. However, due to the minor increase of the carrier lifetime, this is still a bit above the value one can obtain theoretically considering purely the known decrease of the open circuit voltage caused by the increased intrinsic charge carrier concentration at higher temperatures.

Introducing the Second-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations—II: Illustrative Application to Heat and Energy Transfer in the Nordheim–Fuchs Phenomenological Model for Reactor Safety

This work presents an illustrative application of the newly developed “Second-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations (2nd-FASAM-NODE)” methodology to determine most efficiently the exact expressions of the first- and second-order sensitivities of NODE decoder responses to the neural net’s underlying parameters (weights and initial conditions). The application of the 2nd-FASAM-NODE methodology will be illustrated using the Nordheim–Fuchs phenomenological model for reactor safety, which describes a short-time self-limiting power transient in a nuclear reactor system having a negative temperature coefficient in which a large amount of reactivity is suddenly inserted. The representative model responses that will be analyzed in this work include the model’s time-dependent total energy released, neutron flux, temperature and thermal conductivity. The 2nd-FASAM-NODE methodology yields the exact expressions of the first-order sensitivities of these decoder responses with respect to the underlying uncertain model parameters and initial conditions, requiring just a single large-scale computation per response. Furthermore, the 2nd-FASAM-NODE methodology yields the exact expressions of the second-order sensitivities of a model response requiring as few large-scale computations as there are features/functions of model parameters, thereby demonstrating its unsurpassed efficiency for performing sensitivity analysis of NODE nets.

Exploring giant dielectric constant in Dy2CoMnO6: evidence of non-overlapping small polaron hopping

Abstract Perovskites, both natural and synthetic, form a large class of materials are a vast class of materials with significant technological relevance due to their remarkable physical properties, such as superconductivity, magnetoresistance, ionic conductivity, and diverse dielectric behaviors. In this study, the dielectric relaxation and transport properties of the double perovskite Dy2CoMnO6(DCMO) synthesized via high-energy ball milling are investigated. DCMO exhibits a notably large dielectric constant, attributed to a combination of intrinsic and extrinsic mechanisms. Frequency-dependent dielectric studies reveal non-Debye-like behavior, validated by augmented Havriliak-Negami function fitting. Impedance spectroscopy confirms the semiconducting nature of DCMO, showing a negative temperature coefficient of resistance, and identifies two distinct relaxation processes corresponding to grain boundaries and grain interiors thereby highlighting the impact of microstructure and defects. The Cole-Cole plot further supports the non-Debye behavior, while thermally activated relaxation suggests damped charge carrier dynamics at grain boundaries. Conduction analysis using augmented Jonscher's power law reveals non-overlapping small polaron tunneling as the dominant mechanism driving both the dielectric response and transport properties, with DC conductivity suggesting a three-dimensional variable range hopping model. These results provide significant insights into the dielectric and transport properties of DCMO, highlighting its promising potential for advanced electronic applications.

Temperature During Convective Drying of Thin Flat Wet Materials

. The basic laws of the kinetics of drying thin flat materials during the period of drop in the drying speed are outlined. A method for calculating the average integral temperature of wet material on the basis of the relative temperature coefficient of drying is presented. Experimental data are processed based on the relative drying rate in the drying processes of ceramics, asbestos, and woolen fabric. A formula for calculating the average temperature is proposed. The solution of the differential equation of thermal conductivity for a wet plate during the drying process (namely during the period of drop in the drying speed) under boundary conditions taking into account the conditions of drying is given. The calculation of the heat transfer coefficient is given, too. Based on the study of various sources and processing of experimental results, formulas for calculating the thermal conductivity coefficient of wet materials have been presented. The analytical solution of the problem confirmed that during convective drying in low-intensity processes of the second drying period, the temperature change with a decrease in moisture content turns from an exponential dependence smoothly into a linear one, which is completely consistent with the experiment. A comparison of the temperature calculation by the experimental formula with the results of analytical solutions has been presented. A sufficiently reliable coincidence of experimental and calculated analytical values of temperature for the period of drop in speed drying of ceramics, asbestos, and fabric is obtained.

Effect of Interface Bonding on Optimizing the Heat Transfer in Substrate Board With an Array of Heat Sources

ABSTRACTEffective heat distribution in electronic circuitry is essential to improve the performance and life of electronic components such as chips. This study presents a numerical analysis of heat transfer on a substrate board populated with an array of discrete heat sources, assumed to be placed in a horizontal air channel for forced convection cooling. The analysis of electronic packages is performed, taking into consideration the effect of thermal contact conductance (TCC) between the heat source (chip) and the substrate board. The dependence of the temperature distribution on the Reynolds number of air at the inlet and the heating power from the heat source is investigated for inlet velocities ranging from 0.6 to 1.4 m/s and observed to be significant. Temperature and heat transfer coefficient are observed to systematically increase with the increase in the heat dissipation from the heat source. Two configurations—inline and staggered—are analyzed, with the staggered configuration showing superior cooling performance. This improvement is attributed to the fact that staggered arrangements expose fewer heat sources to pre‐heated air before it exits the system. Additionally, the location of the heat source reaching the highest temperature is found to be highly dependent on the TCC of the bonding material between the heat source and the substrate. A hybrid optimization strategy is employed, by combining Artificial Neural Network (ANN) and Genetic Algorithm (GA) for optimizing the location of heat sources. ANN is used for predicting the temperature distribution, subsequently followed by GA to minimize the maximum temperature attained by the heat generating source by varying other control variables like TCC thickness, inlet velocity, and heat generation. The thickness of the bonding layer is varied from 0.225 to 0.271 mm and the heat generation is varied from 1000 to 2000 W/m2. Among them, TCC is observed to be an important parameter controlling the optimum location of heat generating sources. The results obtained from the proposed hybrid optimization strategy are compared with the simulation results and observed to be reasonably close.

Phosphorus diffusion model in surrounding rock from phosphogypsum-based cemented paste backfill under multifactor coupling effect

Abstract Phosphogypsum (PG) is filled in the solidified filling body formed in the goaf of underground mines, and its leaching of toxic and harmful ions infiltrates and spreads to the groundwater in the surrounding rock, and there is a potential risk of environmental pollution. In order to grasp the diffusion law of pollutant ions in surrounding rock from phosphogypsum-based cemented paste backfill (PCPB), the diffusion coefficient equation of P ions in surrounding rock was established based on the electrolyte solution theory, taking phosphorus (P) ions leached from PCPB as the research object. Adopting Fick’s second law, the diffusion model of P ions in the surrounding rock from PCPB under multi-factor coupling was established by comprehensively considering the effects of multiple factors such as P ion binding capacity in the surrounding rock, time dependence of P ions diffusion coefficients, structural defects of the surrounding rock, stress level, temperature, and so on, and the effects of different factors on the diffusion of P ions in the surrounding rock were analysed. The results show that the larger the concentration of P ions in the surrounding rock, the larger the diffusion coefficient is. The larger the diffusion distance is, the smaller the concentration of P ions in the surrounding rock is. P ions binding capacity and time are negatively correlated with the diffusion coefficient, and the coefficient of deterioration effect of the surrounding rock, the coefficient of stress influence and temperature are positively correlated with the diffusion coefficient. Temperature is the most significant factor affecting the diffusion coefficient of P ions, and after a temperature of 40 °C, the diffusion coefficient of P ions increases rapidly.

Extraction and recovery of rare earth elements from NdFeB waste using bismuth reinforced by supergravity

NdFeB stands as the foremost utilized material in permanent magnet applications, generating substantial quantities of NdFeB magnet waste annually. These wastes contain 20−30 wt. % rare earth elements (REEs) and are valuable secondary resources. In this paper, Bi was used as extractant to recover REEs in NdFeB waste by pyrometallurgy, and excess Bi was separated by supergravity technology for recycling. The migration and diffusion behaviors of REEs during the extraction process were investigated, with the diffusion coefficient of REEs in Bi obtained. The influence of Bi-to-waste mass ratio on rare earth extraction efficiency in smelting process, alongside the effect of temperature and gravity coefficient on the Bi recovery rate in supergravity centrifugation process were delineated. Findings revealed that the diffusion of Nd in Bi and NdFeB conformed to Fick's second law. Notably, with a Bi-to-waste mass ratio surpassing 1:1, spontaneous separation occurred between the Bi and Fe phases, facilitating the migration of almost all REEs from NdFeB waste into the Bi phase. Under the optimal conditions (Bi/NdFeB mass ratio of 4:3, separation temperature of 500°C and a gravity coefficient of 1000), the recovery rate of REEs during the smelting stage reached 99.6%, while the Bi recovery rate during the supergravity stage was 74.7%. Additionally, the overall REE recovery rate and Bi recovery rate during the entire process reached 99.3% and 70.3%, respectively. The successful development of this process has opened up a new way for recycling REEs from NdFeB waste.

Temporal variability of ozone and its precursors at tropical megacity, Bengaluru, India: Effect of volatile organic compounds and meteorology

Routine observations of surface ozone (O3) and its precursors (NO, NO2, NOx) were taken over Bengaluru, a southern megacity, India, for 4 years period between January 2015 and December 2018. The seasonal variations of O3, NO, NO2, and NOx have been analysed to understand the short-term variability of the pollutants at this site. The magnitude of O3 varied significantly by season, with maximum concentration during winter (13.07 ppbv) and minimum concentration during monsoon (9.52 ppbv). The highest concentration was observed in the post-monsoon season (17.38 ppbv) for NO, while NO2 and NOx showed the highest (41.75, 50.42 ppbv) in the winter season. The lowest concentrations of NO (5.70 ppbv), NO2 (30.43 ppbv) and NOx(36.28 ppbv) were observed in summer. An estimate was performed to determine the site's VOC-NOx sensitivity, using the TNMHC/NOX ratio as a photochemical measure. This ratio indicates that the study region is NOX responsive in all seasons. Analysis was done on the effects of meteorological factors such as temperature, water vapour, and ventilation coefficient on pollutants. Higher correlation of O3 with temperature showed the role of photochemical reactions in the formation of ozone and water vapour content leads to the removal of ozone concentration. The influence of meteorological variables on NO2 and TNMHC did not appear to be very significant. An analysis of CAMS data with real-time measurements of ozone and oxides of nitrogen showed that ozone is significantly correlated, while nitrogen oxides are not significantly correlated with CAMS data.

Analysis of thermal significances of nanofluids in inclined magnetized flow with Joule heating source and slip effects

The growing need for effective thermal management systems in engineering applications will improve performance by using nanofluids. Nanofluids, which show enhanced thermal characteristics compared to typical fluids, offer an effective way for heat transmission processes in industries. This study is particularly useful for systems where traditional fluids are insufficient for improving thermal performance. Understanding the overall impacts of Joule heating, magnetic fields, and slip conditions would be beneficial in fields such as aircraft, microelectronics, and biomedical engineering.The thermal significances of nanofluids in an inclined magnetized flow are analyzed in this work, taking slip effects and the Joule heating source into account. The motivation behind the current research is to investigate the flow and heat transfer behavior of magnetohydrodynamic (MHD) nanofluid under the influence of Joule heating in the presence of slip conditions.Based on conservation laws and suitable boundary conditions, the governing formulas for mass, momentum, energy, and nanoparticle concentration are developed. In this thermal investigation, unsteady nanofluid flow in two dimensions via a nonlinear stretched configuration is studied numerically together with an example of a non-uniform heat source. Using similarity transformation, the governing partial differential equation for chemical radiation and slip effects parameters for hydromagnetic flow is transformed into a set of ordinary differential equation (ODE). To solve these equations, a numerical method is applied. This study found that the velocity, mass transfer, temperature, concentration, heat transfer, and skin friction coefficient are significantly influenced by the chemical reaction, radiation parameter, and velocity slip. A graphical representation of the parameters influencing the heat transfer and the velocity changes in calculation is observed.

BCZT/LSMO/BCZT sandwich film: Toward high-temperature energy storage capacitors

Ba0.85Ca0.15Zr0.1Ti0.9O3/La0.8Sr0.2MnO3/Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT/LSMO/BCZT) sandwich thin film was deposited on Pt/TiO2/SiO2/Si substrate using sol-gel process. The dielectric properties displayed excellent thermal stability, with the temperature coefficient of capacitance TCC remaining within ± 10 % between -50 °C and 300 °C. The high-energy storage density Wrec of 11.8 J/cm3 observed in the sandwich thin film was nearly twice as high as that of the single BCZT thin film, with high efficiency η of 79 % and responsivity ξRT = Wrec /Eapp of 0.016 J/kV.cm2 under a weak electric field of 800 kV/cm. Furthermore, the stabilities of Wrec and η were observed over a wide temperature range. Interestingly, a high value of Wf = Wrec/(1-η) (> 60 J/cm3) from room temperature up to 300 °C was observed for BCZT/LSMO/BCZT thin film (three times higher than that of the single BCZT thin film), making the sandwich thin film promising candidate for high-temperature energy storage capacitors.

Dielectric, structural and optical properties of lead-free Ba4(Dy2-xBix)Fe2Nb8O30 ferroelectrics

ABSTRACT A series of novel lead-free tungsten bronze-structured Ba4(Dy2-xBix)Fe2Nb8O30 (x = 0, 0.05, 0.1, 0.15, 0.2 and 0.25) were formulated by the traditional high-temperature solid-state method using ball milling for 30 hrs and calcined at 1115°C. The structural property was investigated using X-ray diffraction and Fourier transform infrared spectroscopy. The tetragonal structure with the P4bm space group was confirmed from Rietveld analysis. The scanning electron micrograph shows a uniform distribution of different-shaped grains with less porosity. The UV-vis analysis shows that the materials have band gaps in the range of 2.45–2.51 eV which makes them useful for photocatalytic applications. From photoluminescence analysis, it is confirmed that the samples can be used as violate-/blue light-emitting diodes. The impedance of the materials falls off with the rise in temperature showing their negative temperature coefficient behaviour. The variation of polarization with an electric field confirms the ferroelectric nature of the samples.

U-Shaped Dimeric Acceptors for Balancing Efficiency and Stability in Organic Solar Cells.

Despite significant improvements in power conversion efficiencies (PCEs) of organic solar cells (OSCs), achieving excellent stability remains a great challenge to their commercial feasibility. Here, U-shaped dimeric acceptors (5-IDT and 6-IDT) with different molecular lengths are introduced into the binary OSCs as a third component, respectively. The introduction of the third component effectively reduces the energetic disorder and non-radiative voltage losses and improves the exciton dissociation and charge transport of the devices. Consequently, the PCEs of the 6-IDT- and 5-IDT-treated OSCs are significantly improved to 19.32% and 19.96%, respectively, which is the highest PCE for oligomeric acceptors-based ternary OSCs to date. Meanwhile, the thermal stability of the treated devices is dramatically improved, with the initial efficiency retention of the 6-IDT- and 5-IDT-treated devices increasing from 18% to 32% and 75%, respectively, after 1000h of thermal stress. This is mainly attributed to the ability of the smaller molecular length of 5-IDT to stabilize the phase-separated morphology of the polymeric donor and small molecular acceptor, rather than the high glass transition temperature and low diffusion coefficient.

A 0.7‐V 7.4‐nW 6.4‐ppm/°C CMOS Subthreshold Voltage Reference With Temperature Compensation Circuit

ABSTRACTThis paper proposes a nanowatt voltage reference (VR) with temperature coefficient compensation. All transistors work in the subthreshold region. The complementary‐to‐absolute‐temperature (CTAT) voltage and proportional‐to‐absolute‐temperature (PTAT) voltage are mainly generated by two NMOS transistors with different threshold voltages. At the same time, a simple temperature compensation circuit is designed to optimize the temperature coefficient at high temperatures, so that the proposed VR circuit can generate a reference voltage with a wider temperature range and a lower temperature coefficient. The proposed VR circuit is implemented using a standard 0.18‐μm CMOS process with an active area of only 0.022 mm2. The postlayout simulation results show that the proposed VR circuit generates a reference voltage of 308.21 mV at room temperature. Its temperature coefficient is 6.4 ppm/°C over a temperature range of −40°C°C–140°C, with a power consumption of 7.4 nW. The voltage line sensitivity (LS) is 0.098%/V, and the power supply ripple rejection (PSRR) is −72 dB @DC and −42 dB @10 MHz.