Planar Thermoelectric Microgenerators in Application to Power RFID Tags

This paper presents an innovative approach to the integration of thermoelectric microgenerators (μTEGs) based on thick-film thermopiles of planar constantan-silver (CuNi-Ag) and calcium cobaltite oxide-silver (Ca3Co4O9-Ag) thick-film thermopiles with radio frequency identification (RFID) technology. The goal was to consider using the TEG for an active or semi-passive RFID tag. The proposed implementation would allow the communication distance to be increased or even operated without changing batteries. This article discusses the principles of planar thermoelectric microgenerators (μTEGs), focusing on their ability to convert the temperature difference into electrical energy. The concept of integration with active or semi-passive tags is presented, as well as the results of energy efficiency tests, considering various environmental conditions. On the basis of the measurements, the parameters of thermopiles consisting of more thermocouples were simulated to provide the required voltage and power for cooperation with RFID tags. The conclusions of the research indicate promising prospects for the integration of planar thermoelectric microgenerators with RFID technology, opening the way to more sustainable and efficient monitoring and identification systems. Our work provides the theoretical basis and practical experimental data for the further development and implementation of this innovative technology.

Microstructural, Thermoelectric and Mechanical Properties of Cu Substituted NaCo2O4

Polycrystalline samples of NaCo_2−xCu_xO₄ (x = 0, 0.01, 0.03, 0.05) were obtained from powder precursors synthesized by a mechanochemically assisted solid-state reaction method (MASSR) and a citric acid complex method (CAC). Ceramic samples were prepared by pressing into disc-shaped pellets and subsequently sintering at 880 °C in an argon atmosphere. Effects of low concentrations of Cu doping and the above-mentioned synthesis procedures on the thermoelectric and mechanical properties were observed. The electrical resistivity (ρ), the thermal conductivity (κ) and the Seebeck coefficient (S) were measured simultaneously in the temperature gradient (ΔT) between the hot and cold side of the sample, and the figure of merit (ZT) was subsequently calculated. The ZT of the CAC samples was higher compared with the MASSR samples. The highest ZT value of 0.061 at ΔT = 473 K was obtained for the sample with 5 mol% of Cu prepared by the CAC method. The CAC samples showed better mechanical properties compared to the MASSR samples due to the higher hardness of the CAC samples which is a consequence of homogeneous microstructure and higher density obtained during sintering of these samples. The results confirmed that, besides the concentration of Cu, the synthesis procedure considerably affected the thermoelectric and mechanical properties of NaCo₂O₄ (NCO) ceramics.

Novel Ultrahigh-Performance ZnO-Based Varistor Ceramics

The nonlinear response of a material to an external stimulus is vital in fundamental science and technical applications. The power-law current-voltage relationship of a varistor is one such example. An excellent example of such behavior is the power-law current-voltage relationship exhibited by Bi₂O₃-doped ZnO varistor ceramics, which are the cornerstone of commercial varistor materials for overvoltage protection. Here, we report on a sustainable, ZnO-based varistor ceramic, without the volatile Bi₂O₃, that is based on Cr₂O₃ as the varistor former and oxides of Ca, Co, and Sb as the performance enhancers. The material has an ultrahigh α of up to 219, a low I_L of less than 0.2 μA/cm², and a high E_b of up to 925 V/mm, making it superior to state-of-the-art varistor ceramics. The results provide insights into the design of materials with specific characteristics by tailoring states at the grain boundaries. The discovery of this ZnO-Cr₂O₃-type varistor ceramic represents a major breakthrough in the field of varistors for overvoltage protection and could drastically affect the world market for overvoltage protection.

Improvement in the thermoelectric properties of porous networked Al-doped ZnO nanostructured materials synthesized via an alternative interfacial reaction and low-pressure SPS processing

This work presents a novel, simpler and faster bottom-up approach to produce relatively high performance thermoelectric Al-doped ZnO ceramics from nanopowders produced by interfacial reaction followed by consolidation with Spark Plasma Sintering.

Phonon Scattering and Electron Doping by 2D Structural Defects in In/ZnO

In/ZnO bulk compounds have been synthesized using a simple solid-state process. In this study, both the structural features and thermoelectric properties of the Zn_1-xIn_xO series with ultralow indium content (0 ≤ x ≤ 0.02) have been studied. High-angle annular dark-field scanning transmission electron microscopy analyses highlight that indium has the ability to create multiple basal plane and pyramidal defects that produce ZnO domains with inverted polarity starting from dopant concentrations as low as 0.25 atom %. Interestingly, the formation of parallel inversion boundaries consisting of InO₆ octahedra in the ZnO₄ tetrahedra matrix is responsible for phonon scattering while increasing electrical conductivity, thereby enhancing the thermoelectric properties. This effect of multiple extended two-dimensional defects on the thermoelectric properties of ZnO is reported for the first time with such low indium doping. On the chemistry side, the present results point toward a lack of In solubility in the ZnO structure. Moreover, this study is a step forward to the synthesis of other thermoelectric compounds where dopant-induced planar defects in bulk transition metal compounds have the potential to enhance both phonon scattering and electronic conductivity.

Structural characterization of self-assembled ZnO nanoparticles obtained by the sol-gel method from Zn(CH3COO)2·2H2O

Zinc oxide nanopowders were synthesized by the sol-gel method from an ethanol solution of zinc acetate dihydrate. Detailed structural and microstructural investigations were carried out using x-ray diffraction, Raman spectroscopy, thermogravimetric and differential thermal analyses, as well as high-resolution transmission electron microscopy (TEM) and field-emission scanning electron microscopy. The intermediate compound of the reaction was layered zinc hydroxide acetate that further transforms into hexagonally shaped ZnO crystalline nanoplates (d(m) = 4 nm), which aggregate into larger spherical particles. According to the TEM analysis the ZnO nanoparticles were self-assembled into larger particles with the same orientation, i.e. aligned lattice planes of the particles. A further solvothermal treatment resulted in hexagonal, prismatic ZnO mesocrystals.

Short-term effect of acarbose on specific intestinal disaccharidase activities and hyperglycaemia in CBA diabetic mice

The purpose of this study was to examine the short-term effects of 75, 100 and 150 mg of acarbose mixed in 100 g standard laboratory chow on specific intestinal disaccharidase activities and on hyperglycaemia in diabetic CBA strain mice on standard diet. The small intestine was excised and divided into three segments, from pylorus to duodenum, and two equal lengths of the jejunum and ileum of control and diabetic mice with or without added acarbose. Specific maltase and sucrase activities were determined using maltose and sucrose as substrates respectively. Increased specific activities of maltase and sucrase were detected in the intestines of CBA mice on standard laboratory diet seven days after alloxan-induced diabetes. Feeding for 7 days with 75, 100 or 150 mg acarbose uniformly mixed in 100 g standard laboratory chow, induced a decrease in the specific maltase and sucrase activities, compared with diabetic mice on standard laboratory diet. Feeding with 75 mg acarbose mixed in 100 g standard laboratory chow caused a statistically significant decrease of maltase in the duodenum and of sucrase in duodenum and jejunum, without a antihyperglycaemic effect. Feeding with 100 or 150 mg caused statistically significant decreases in specific maltase and sucrase activities in duodenum, jejunum and ileum. An antihyperglycaemic effect was observed only in the group of diabetic mice fed with 100 mg acarbose. This indicates that the antihyperglycaemic effect of acarbose involves factors other than these, related only to its inhibitory effect on disaccharidase activities.

Primary gastrointestinal non-Hodgkin's lymphoma: increasingly AIDS-related

A retrospective study was conducted to determine the influence of the acquired immunodeficiency syndrome (AIDS) epidemic on the incidence, clinical presentation, and outcome of primary gastrointestinal lymphoma (stages I and II) over a 20-year period at a single institution. Between 1971 and 1981, there were seven cases. Fifty-eight patients were diagnosed between 1983 and 1993, and 81 per cent were AIDS-related. The mean age overall was 50 years; 81 per cent were male, and 35 per cent presented with acute complications. All tumors were high or intermediate grade B cell lymphomas, and 48 per cent had bulky or advanced disease at presentation. The overall actuarial 5-year survival was 9 per cent. Human immunodeficiency virus status and stage were significant independent prognostic factors. The AIDS-related subgroup had a mean age of 43 years, and 91 per cent were male. Tumor resection was performed in 38 per cent, and the 5-year survival was 2 per cent. The mean age for the non-AIDS-related subgroup was 71 years, and 55 per cent were male. Resection was performed in 39 per cent, and 5-year survival was 28 per cent. AIDS-related disease accounted for the dramatic increase in incidence of primary gastrointestinal lymphoma since 1983. The prognosis for these patients is poor and is dominated by the underlying immunocompromise.