Dry Nitrogen Atmosphere Research Articles

Evaluation of a Commercial MoS2 Dry Film Lubricant for Space Applications

Molybdenum disulfide coatings, particularly Microseal 200-1, have been extensively used as dry film lubricants for actuating mechanisms in space applications. Although Microseal 200-1 has historically been a popular choice for space missions, recent assessments indicate a need for reexamination. This study evaluates sliding friction in air and dry gaseous nitrogen atmospheres at ambient temperatures with both linear reciprocating and rotary unidirectional tribo-tests. Measurements are performed for Microseal 200-1 applied on substrates and surface treatments commonly used in aerospace components, particularly stainless steel and a titanium alloy. Our findings indicate that the friction of stainless steel balls sliding on Microseal 200-1-coated disks is significantly influenced by the environment as well as the disk substrate material. The average friction coefficient ranges from 0.12 to 0.48 in air and from 0.04 to 0.41 in dry gaseous nitrogen, and the amount of friction is consistently much higher for the Microseal 200-1 on the stainless steel than on the titanium alloy. Microscopy and surface analyses, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray fluorescence, of the coatings on stainless steel substrates reveals that the coatings are sparse and relatively thin, likely a key factor contributing to their high friction. This insight underscores the substrate dependence of this widely used coating and highlights the importance of detailed tribological testing in accurately assessing the tribological performance of commercial dry film lubricants, a key step towards improving the reliability and effectiveness of actuating mechanisms for space applications.

Enhanced electrochemical performance of Ba0.5Sr0.5Co0.8Fe0.2O3-δ cathode by Zr4+, Sm3+ and Yb3+ tri-doped BaCeO3 compositing for intermediate-temperature thin-film fuel cells

In this study, Zr4+, Sm3+ and Yb3+ tri-doped BaCeO3 (BaCe0.7Zr0.1Sm0.1Yb0.1O3-α) was prepared using a citric acid-EDTA combined complexing sol-gel method. The influence of sintering aid (CuO) content on structure, sinter-ability and conductivity of BaCe0.7Zr0.1Sm0.1Yb0.1O3-α (BCZSY) was studied using XRD, SEM and AC impedance. XRD patterns of different sintering aid contents and temperatures showed that all samples formed a pure BaCeO3 orthorhombic phase without any impurities. The conductivity of 1500-BCZSY reached 1.8 × 10−2 S cm−1 and 1.9 × 10−2 S cm−1 in dry nitrogen and hydrogen atmospheres at 700 °C, respectively. The anode-supported membrane fuel cells of NiO-BCZSY | BCZSY (13 μm) | Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) and NiO-BCZSY | BCZSY (15 μm) | BCZSY-BSCF were fabricated, respectively. SEM results showed that the cathode, anode-support and electrolyte had good adhesion. The polarization resistance (Rp) of BCZSY-BSCF was significantly reduced by 34 %, 44 % and 55 % compared to BSCF at 500 °C, 550 °C and 600 °C, respectively. The maximum power density (Pmax) using BCZSY-BSCF as the cathode increased by 18 %, 17 % and 22 % compared to BSCF at 500 °C, 550 °C and 600 °C under the condition of slightly higher electrolyte film thickness, correspondingly.

Weathering of a Polyurethane-Based Gel Electrolyte

A recently described flexible polyurethane electrolyte was artificially weathered at 25/50 °C and 50% r.h. in air and at 25 °C in a dry nitrogen atmosphere, each with and without UV irradiation. Different formulations and the polymer matrix, used as a reference, were weathered in order to investigate the influence of the amount of conductive lithium salt and the solvent propylene carbonate. The complete loss of the solvent at a standard climate was already observed after a few days, strongly influencing the conductivity and mechanical properties. The essential degradation mechanism appears to be the photo-oxidative degradation of the polyol's ether bonds, which leads to chain scission, oxidation products and negative changes in the mechanical and optical properties. A higher salt content has no effect on the degradation; however, the presence of propylene carbonate intensifies the degradation.

Investigating the effect of fused deposition modelling on the tribology of PETG thermoplastic

A widely recognized consequence of the additive manufacturing process is the deterioration of mechanical properties through the development of macrodefects, microdefects, and chemical changes. This has particularly negative impacts on fatigue and wear resistance of components produced by additive manufacturing, which limits the utility of the technology for engineering applications. In this investigation, we find that glycol-modified polyethylene terepthalate processed via Fused Deposition Modelling (FDM) exhibits a significantly lower wear rate as compared to virgin material when subjected to slow-speed dry sliding contact, which is a rare case of an additively-manufactured material with improved bulk properties. Using pin-on-disk testing, we demonstrate favorable wear resistance for additively-manufactured pins against a surface ground 440c stainless steel counterface, which reflects potential utility of the material in light-duty, low-maintenance linear and rotary motion applications. The wear behavior observed under these test conditions corresponds to an order of magnitude decrease in wear relative to existing literature. Annealing the samples results in a further decrease in wear rate, while samples produced in a dry nitrogen atmosphere exhibit increased wear and a change in morphology and thickness of the transfer film. X-ray photoelectron spectroscopy testing validates that FDM printing results in material oxidation, that this oxidation corresponds with an improvement in wear performance, and that printing in a dry nitrogen environment inhibits this change.

An investigation of the reaction of uranium with nitrogen - A thermogravimetric analysis study

In this work, the heating corrosion reaction of uranium with dry air and with dry nitrogen gas was investigated. Metallic uranium samples of different specific surface area and mass were reacted in a thermogravimetric analysis system at temperature ramping from 323 K to 1273 K at 15 K.min−1. Ignition was achieved during all heating profiles of the samples reacting with air, with the reported ignition temperature decreasing with increasing specific surface area. Heating cycles were conducted for the uranium and dry nitrogen gas system to investigate if ignition could be attained. These experiments were conducted by varying the specific surface area, sample mass, initial oxide thickness, nitrogen flow rate, and heating ramp rate. None of these experiments showed signs of clear ignition under dry nitrogen. It is hence suggested that uranium ignition under a dry nitrogen atmosphere is not readily attainable and would require a combination of extreme conditions, such as high heating ramp rate for a non-oxidised sample of high surface area and mass.

A Strong and Rigid Coordination Adaptable Network that Can Be Reprocessed and Recycled at Mild Conditions

A Strong and Rigid Coordination Adaptable Network that Can Be Reprocessed and Recycled at Mild Conditions

Oxygen Kinetic Isotope Effects in the Thermal Decomposition and Reduction of Ammonium Diuranate.

Oxygen stable isotopes in uranium oxides processed through the nuclear fuel cycle may have the potential to provide information about a material’s origin and processing history. However, a more thorough understanding of the fractionating processes governing the formation of signatures in real-world samples is still needed. In this study, laboratory synthesis of uranium oxides modeled after industrial nuclear fuel fabrication was performed to follow the isotope fractionation during thermal decomposition and reduction of ammonium diuranate (ADU). Synthesis of ADU occurred using a gaseous NH3 route, followed by thermal decomposition in a dry nitrogen atmosphere at 400, 600, and 800 °C. The kinetic impact of heating ramp rates on isotope effects was explored by ramping to each decomposition temperature at 2, 20, and 200 °C min–1. In addition, ADU was reduced using direct (ramped to 600 °C in a hydrogen atmosphere) and indirect (thermally decomposed to U3O8 at 600 °C, then exposed to a hydrogen atmosphere) routes. The bulk oxygen isotope composition of ADU (δ18O = −16 ± 1‰) was very closely related to precipitation water (δ18O = −15.6‰). The solid products of thermal decomposition using ramp rates of 2 and 20 °C min–1 had statistically indistinguishable oxygen isotope compositions at each decomposition temperature, with increasing δ18O values in the transition from ADU to UO3 at 400 °C (δ18OUO3 – δ18OADU = 12.3‰) and the transition from UO3 to U3O8 at 600 °C (δ18OU3O8 – δ18OUO3 = 2.8‰). An enrichment of 18O attributable to water volatilization was observed in the low temperature (400 °C) product of thermal decomposition using a 200 °C min–1 ramp rate (δ18OUO3 – δ18OADU = 9.2‰). Above 400 °C, no additional fractionation was observed as UO3 decomposed to U3O8 with the rapid heating rate. Indirect reduction of ADU produced UO2 with a δ18O value 19.1‰ greater than the precipitate and 4.0‰ greater than the intermediate U3O8. Direct reduction of ADU at 600 °C in a hydrogen atmosphere resulted in the production of U4O9 with a δ18O value 17.1‰ greater than the precipitate. Except when a 200 °C min–1 ramp rate is employed, the results of both thermal decomposition and reduction show a consistent preferential enrichment of 18O as oxygen is removed from the original precipitate. Hence, the calcination and reduction reactions leading to the production of UO2 will yield unique oxygen isotope fractionations based on process parameters including heating rate and decomposition temperature.

Synthesis and Characterization of Date Palm Fiber-Based Bio-Char and Activated Carbon and its Utilization for Environmental Remediation

Natural agricultural products have the potential to be a substitute for synthetic polymers absorbentsin environmental remediation and spill cleanup and recovery. One of these natural by-productswhich is available in many regions of the world is Date Palm Fibers (DPF). DPF (also known assurface fibers) is a natural sorbent that exhibits good sorption characteristics. In an attempt tovalorize this abundant, low cost byproduct, we have investigated the micro porosity of this rawmaterial by carrying out two procedures. First, hydrothermal pyrolysis using a scalable reactor withonly water as solvent at high temperature (480 °C) under dry nitrogen atmosphere. Biochar yield wasfound varying from 30.5 to 33.6% (32%), with little bio-oil.Then the resultant biochar was physically activated with KOH and the mixture heated to 750oC(0.5oC/min) and kept at 750°C for 2 hours under Argon flow in a tubular furnace to produceactivated carbon. Second, the resulting biochar and activated carbons were then characterized byParticle Analyzer to measure their surface area, pore volume and pore diameter.For biochar, surface area : 1.1374 m²/g, pore volume 0.001883 cm³/g, pore diameter 1355.874 Å andfor activated biochar (activated carbon), surface area : 1220.2755 m²/g, pore volume: 0.062068cm³/g, pore diameter: 19.0116 Å were determined by particle characterization analyzer. ScanningElectron Microscopy (SEM), and X-ray Diffraction (XRD) was also used for other analysis .The oil sorption behavior of the raw DPF, biochar and activated biochar were examined with motoroil. The Oil Sorption Capacity (OSC) of raw DPF, biochar and activated biochar were tested with theoil as oil alone and an oil over water surface and the value calculated gravimetrically. The maximumOSC values of the sorbents were in the order of: DPF<biochar< activated Biochar with OSC valuesof 8.952, 11.712 and 33.402 g*oil/g*sorbent, respectively at a sorption time of 30 min. That indicatethe OSC of the sorbents above are proportional with its surface areas.The sorbent materials can be utilized in oil spill remediation as well as waste water treatment forremoval of hydrocarbons pollutants from water. In addition biochar can be used as a soil amendmentfor enhancing soil fertility

Influence of Alumina Dopant and Environment on the Electrical Properties of Calcium Copper Titanate Ceramics.

Calcium copper titanate (CaCu₃Ti₄O12; CCTO) ceramics are useful as capacitor dielectrics for many applications. In this study the effect of doping with alumina and testing atmospheres in air and dry N₂ on the stability and reproducibility of electrical and dielectric properties of CCTO-xAl₂O₃ system, where x = 0, 0.5, and 4 wt.% as a function of temperature are investigated. Solid-state synthesis route is used to fabricate the pure and doped CCTO samples sintered at 1080 °C and 1100 °C for 5 h in air. Stable and reproducible dielectric properties are obtained only by switching the measuring atmosphere from air to dry N₂. Increased space charge accumulation at the grain boundaries leading to large dielectric constant (ε') and tan δ are measured in air. Much lower tan δ values of 0.021-0.020 are obtained with a large ε' (8,815-11,090) at low frequencies (500-800 Hz) in N₂ at 23 °C for 0.5 wt.% alumina in both samples sintered at 1080 °C and 1100 °C. These results clearly demonstrate that testing environment can dominate the dielectric properties of pure and alumina-doped CCTO at low frequencies unless measured in dry nitrogen atmosphere to achieve intrinsic behavior useful for applications as capacitors.

Ti3C2/graphene oxide heterostructural coating with enhanced dry tribological performance

Ti3C2/Graphene Oxide (GO), a heterostructural solid lubricant with a self-lubricating performance at both ambient air and dry nitrogen atmosphere, has been investigated. At ambient atmosphere, both the coefficient of friction (COF) and wear rate for Ti3C2/GO coatings show a comparable self-lubricating effect to GO samples. The Ti3C2/GO coatings exhibit significantly four times lower COF alongside 100 times lower wear rate than individual GO coatings, respectively, at the dry nitrogen atmosphere. The mechanism of anti-wear and friction reduction could be attributed to the enhanced stability of Ti3C2/GO heterostructural coating during the sliding process, which continuously generates transferred film and evenly distributed tribo-layer inside wear track at dry nitrogen atmosphere, suppressing the occurrence of abrasive and adhesion.

Improving the reliability of conductive atomic force microscopy-based electrical contact resistance measurements

Electrical contact resistance (ECR) measurements performed via conductive atomic force microscopy (C-AFM) suffer from poor reliability and reproducibility. These issues are due to a number of factors, including sample roughness, contamination via adsorbates, changes in environmental conditions such as humidity and temperature, as well as deformation of the tip apex caused by contact pressures and/or Joule heating. Consequently, ECR may vary dramatically from measurement to measurement even on a single sample tested with the same instrument. Here we present an approach aimed at improving the reliability of such measurements by addressing multiple sources of variability. In particular, we perform current-voltage spectroscopy on atomically flat terraces of highly oriented pyrolytic graphite (HOPG) under an inert nitrogen atmosphere and at controlled temperatures. The sample is annealed before the measurements to desorb adsorbates, and conductive diamond tips are used to limit tip apex deformation. These precautions lead to measured ECR values that follow a Gaussian distribution with significantly smaller standard deviation than those obtained under conventional measurement conditions. The key factor leading to this improvement is identified as the switch from ambient conditions to a dry nitrogen atmosphere. Despite these improvements, spontaneous changes in ECR are observed during measurements performed over several minutes. However, it is shown that such variations can be suppressed by applying a higher normal load.

Tribochemical mechanism of superlubricity in graphene quantum dots modified DLC films under high contact pressure

In this work, we designed three series of tribo-couples based on amorphous carbon films including GLC, DLC and PLC that were modified by graphene quantum dots (GQDs). The tribo-testing environment was controlled at harsh conditions (like heavy load and high speed) in dry nitrogen atmosphere using bare and film-coated bearing steel balls as counterbodies, respectively. Through the tribochemical interactions, the self-mated DLC system obtained a surperlubricity state (μ = 0.01). During the whole sliding, the contact surface of the upper counterfacing ball was covered by 2D-layered carbon and graphitic lubricants induced via structural transformation of GQDs. Meanwhile, the tribofilm of the disc wear track was composed of a silica-like SiOx boundary layer and a multicomponent mixed-layer induced by tribochemistry. Compared to the self-mated DLC system, the structural boundary enriched with SiOx compounds was not formed at the bottom region of the tribofilm for the bare steel system; meanwhile, the disc wear track was covered by a thicker tribofilm containing plenty of degraded GQDs. This inferred the fact that the formation of a nanostructured sliding interface was the key to realize superlubricity. These discoveries successfully afforded a lubrication mechanism of GQDs for solid lubricant in applications of engineering and industry.

A novel Sn0.9Ni0.1P2O7/KPO3 composite electrolyte with improved electrical properties for intermediate temperature fuel cells

In this study, a novel Sn0.9Ni0.1P2O7/KPO3 composite electrolyte was prepared by a mechanical mixing method. The Raman spectrum and X-ray diffraction of Sn0.9Ni0.1P2O7/KPO3 indicated that the main microstructure is pyrophosphate phase and KPO3 mainly exists in amorphous state in the composite. The intermediate temperature (400–700 °C) electrical properties of Sn0.9Ni0.1P2O7/KPO3 were studied by means of electrochemical impedance spectroscopy. The maximum conductivity of Sn0.9Ni0.1P2O7/KPO3 was 6.1 × 10−2 S cm−1 in a dry nitrogen atmosphere at 700 °C. The log σ ～ log (pO2) results showed that Sn0.9Ni0.1P2O7/KPO3 is a pure ionic conductor in an oxidizing atmosphere and a hybrid conductor of proton and electron hole under a reductive atmosphere. The maximum power density of Sn0.9Ni0.1P2O7/KPO3 (thickness: 1.2 mm) was 434 mW cm−2 at 700 °C.

Measuring nanoscale friction at graphene step edges

Although graphene is well known for super-lubricity on its basal plane, friction at its step edge is not well understood and contradictory friction behaviors have been reported. In this study, friction of mono-layer thick graphene step edges was studied using atomic force microscopy (AFM) with a Si tip in dry nitrogen atmosphere. It is found that, when the tip slides over a ‘buried’ graphene step edge, there is a resistive force during the step-up motion and an assistive force during the step-down motion due to the topographic height change. The magnitude of these two forces is small and the same in both step-up and step-down motions. As for the ‘exposed’ graphene step edge, friction increases in magnitude and exhibits more complicated behaviors. During the step-down motion of the tip over the exposed step edge, both resistive and assistive components can be detected in the lateral force signal of AFM if the scan resolution is sufficiently high. The resistive component is attributed to chemical interactions between the functional groups at the tip and step-edge surfaces, and the assistive component is due to the topographic effect, same as the case of buried step edge. If a blunt tip is used, the distinct effects of these two components become more prominent. In the step-up scan direction, the blunt tip appears to have two separate topographic effects elastic deformation of the contact region at the bottom of the tip due to the substrate height change at the step edge and tilting of the tip while the vertical position of the cantilever (the end of the tip) ascends from the lower terrace to the upper terrace. The high-resolution measurement of friction behaviors at graphene step edges will further enrich understanding of interfacial friction behaviors on graphene-covered surfaces.

Aluminum dual doping and oxygen transport pathway in novel Sr11Mo4−xAlxO23 oxide-ion solid electrolytes

Three new electrolytes of composition Sr11Mo4-xAlxO23-δ (x = 0.5, 1.0 and 1.5) were synthesized by wet-chemistry procedures (citrate method) as polycrystalline samples. They were crystallographically studied from synchrotron and neutron diffraction techniques. They derive from the Sr11Mo4O23 complex perovskite, which can be rewritten as Sr1.75□0.25SrMoO5.75, highlighting the relationship with double perovskites A2B′B″O6. From these analyses via Rietveld refinement, a dual doping was found from synchrotron data, where the aluminum is equally allocated at both Sr (B′) and Mo (B″) sites. A detailed analysis of the neutron data from Difference Fourier Maps (DFM) unveiled the oxygen delocalization around the Mo site. From the refined crystal structures at room and high temperatures, a Bond Valence Sum Map (BVSM) analysis was useful to find the oxygen pathway in the crystal structure, and the minimum density to allow connections among oxygen atoms. The structural characterization was complemented with thermogravimetric and thermodilatometric analysis. The ionic conductivity was measured from electrochemical impedance spectroscopy (EIS) in wet and dry air and nitrogen atmospheres.

Modeling the thermal decomposition of friction composite systems based on yarn reinforced polymer matrices using artificial neural networks

AbstractThe presented work deals with the application of artificial neural networks in the modelling of the thermal decomposition process of friction composite systems based on polymer matrices reinforced by yarns. The thermal decomposition of the automotive clutch friction composite system consisting of a polymer blend reinforced by yarns from organic, inorganic and metallic fibres impregnated with resin, as well as its individual components, was monitored by a method of non‐isothermal thermogravimetry over a wide temperature range. A supervised feed‐forward back‐propagation multi‐layer artificial neural network model, with temperature as the only input parameter, has been developed to predict the thermogravimetric curves of weight loss and time derivative of weight loss of studied friction composite system and its individual components acquired at a fixed constant heating rate under a pure dry nitrogen atmosphere at a constant flow rate. It has been proven that an optimized model with a 1‐25‐6 architecture of an artificial neural network trained by a Levenberg‐Marquardt algorithm is able to predict simultaneously all the analyzed experimental thermogravimetric curves with a high level of reliability and that it thus represents the highly effective artificial intelligence tool for the modelling of thermal stability also of relatively complicated friction composite systems.

Development of MEMS MOS gas sensors with CMOS compatible PECVD inter-metal passivation

Metal oxide semiconductor (MOS) based micro-electromechanical sensors (MEMS) for gas measurement were developed using back-end-of-line (BEOL) compatible inter-metal dielectric films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD). As MOS MEMS require sintering above 600°C, a set of PECVD silicon oxide and nitride films was characterized before and after annealing up to 700°C, in order to identify the best candidate inter-metal dielectric materials. The effect of thermal load on the films was determined by measuring stress, thickness and refractive index after annealing both in dry air and nitrogen atmosphere. Nano-indentation was used to estimate the elastic modulus after annealing. The best performing films were employed as inter-metal dielectric in the full fabrication of microheater MEMS gas sensors. Among the selected films, only silicon oxide deposited with high frequency plasma generator allowed for the complete gas sensor fabrication with no damage. SnO2 paste was successfully screen printed on the fabricated membranes and sintered to enable gas sensing. Electrical and gas sensing tests were performed with the fabricated microheaters, demonstrating full functionality. Thermal stress endurance tests were also conducted, with no membrane deformation after more than 500,000 duty cycles. Results show that the proposed PECVD passivation is compliant up to 650°C firing temperature and 450°C operating temperature, and demonstrate the use of CMOS-BEOL PECVD inter-metal passivation for MOS MEMS gas sensor fabrication.

Thermal analysis (TG–DSC, DSC–microscopy and EGA) and characterization of heavy trivalent lanthanides and yttrium isonicotinates

The trivalent lanthanide isonicotinates were synthesized to obtain stoichiometry Lu(IN)3 and Ln(IN)3·2H2O (Ln = Tb to Lu, and Y; IN = isonicotinate). A deep study of the thermal behavior in oxidant (air) and inert (N2) atmospheres was carried out using the following thermoanalytical techniques: simultaneous thermogravimetry and differential scanning calorimetry (TG–DSC), differential scanning calorimetry (DSC) and evolved gas analysis (EGA by TG–DSC–FTIR). From these results, it was possible to determine that dehydration occurs in a single step and the thermal decomposition of the anhydrous compounds occurs in one or two (air), and two or three steps (N2). The final residues of thermal decomposition were Tb4O7 and Ln2O3 (Ln = Dy to Lu, and Y) in air atmosphere, while in N2 atmosphere the mass loss is still being observed up to 1000 °C. The identified gaseous products evolved during the thermal decomposition in dynamic dry air and nitrogen atmospheres were water, CO2, pyridine and CO. From these thermoanalytical data, it was possible to propose a general equation of thermal decomposition of these compounds in the N2 atmosphere. DSC curves of Tb and Ho compounds presented endothermic peaks corresponding to a reversible phase transition, confirmed by powder X-ray diffractometry (XRD), not previously reported. In addition, infrared vibrational spectroscopy (IR) suggests the coordination through carboxylate as bridging bidentate ligand toward the heavy trivalent lanthanides metals. This paper is complementary to our previous study involving the series of light trivalent lanthanides isonicotinates.

Synthesis, Conductivity, and Impedance Studies on Metallophthalocyanines Formed Across Adjacent Rings

The synthesis and characterization of CoII, ZnII, and NiII phthalocyanines (Pcs) 4, 5, and 6, respectively, containing two bis[2‐(4‐hydroxyphenyl)‐2‐propyl]benzene groups formed across adjacent rings at the peripheral positions are described. The Pcs were synthesized by cyclotetramerization of the previously prepared precursor 4,4′‐bis[1,3‐propylbenzene‐2‐p‐phenoxy]phthalonitrile (3) in the presence of metal salt in boiling dry DMF under a dry nitrogen atmosphere. Elemental analysis, UV‐Vis, FT‐IR, and 1H‐NMR spectroscopy, as well as MALDI‐TOF mass spectrometry techniques were used for the characterization of 4. Conductivity (dc and ac) and impedance spectroscopy (IS) measurements were performed on the films of 5 and 6 between the temperatures 293 and 523 K and frequencies 40 and100 kHz. The dc conductivity values were calculated as 2.11 × 10–10, 3.48 × 10–10, and 1.90 × 10–10 S/cm for the films of 4, 5, and 6, respectively, at room temperature. Activation energy values of the films were also calculated. Conductivity (ac) results suggest that the dominant charge transport mechanisms can be explained by the hopping model depending on temperature and frequency range. From impedance spectra and Cole‐Cole plots, the relaxation time in the Debye dispersion relation is considered as a distribution of relaxation time values rather than as a single relaxation time. To elucidate the structural, spectroscopic, and bonding properties of the obtained compounds, DFT/TD‐DFT calculations were performed.

Dielectric Properties of Calcium Copper Titanate Ceramics Exposed to Air and Dry Nitrogen Atmospheres

The stability and consistency of electrical properties displayed by calcium copper titanate (CaCu3Ti4O12–CCTO) ceramics are the most important concern when they are used as capacitor dielectrics. This study investigated the influence of exposure to air and dry N2 atmospheres on dielectric properties of the as-prepared CCTO as a function of temperature. Solid-state synthesis route has been used to fabricate the CCTO sintered pellets at 1100 °C for 5 h in air. Highly inconsistent impedance spectra and dielectric properties are observed in the frequency range from 1 Hz to 1 MHz when the samples are tested in air at 23 °C. In contrast, stable and consistent electrical properties are obtained by testing the samples under dry N2. Value of tanδ as small as 0.014 and a large dielectric constant (e′) of 12,935 ± 2 at 2.2 kHz are obtained when samples are exposed and tested in dry N2 at 23 °C. The details concerning the possible underlying mechanisms responsible for dielectric properties of CCTO are reported in this article.