Search Results (8)

M²⁺N⁴⁺Nb₂O₈-type ceramics (where M = Mg, Ca, Mn, Co, Ni, Zn and N = Ti, Zr) are essential for satellite communication and mobile base stations due to their medium relative permittivity (ε_r) and high quality factor (Q × f). Although ZnTi_0.2Zr_0.8Nb₂O₈ ceramic exhibits impressive microwave dielectric properties, including an ε_r of 29.75, a Q × f of 107,303 GHz, and a τ_f of −24.41 ppm/°C, its sintering temperature of 1150 °C remains a significant barrier for integration into low-temperature co-fired ceramic (LTCC) technologies. To overcome this limitation, a strategy involving the partial substitution of Zn²⁺ with Cu²⁺ and the addition of LiF as a sintering aid was devised for ZnTi_0.2Zr_0.8Nb₂O₈. The dual impact of Cu²⁺ partial substitution and LiF as a sintering enhancer facilitated the successful sintering of Cu_0.3Zn_0.7Ti_0.2Zr_0.8Nb₂O₈ ceramics at a reduced temperature of 950 °C using the conventional solid-state reaction method. These ceramics exhibited excellent microwave dielectric properties. Notably, Cu_0.3Zn_0.7Ti_0.2Zr_0.8Nb₂O₈ ceramic with 40 mol% LiF addition demonstrated optimal microwave dielectric properties without any reaction with a silver electrode at a sintering temperature of 950 °C, yielding ε_r = 32, Q × f = 45,543 GHz, and τ_f = −43.5 ppm/°C. Full article

Nowadays, low-temperature co-fired ceramic (LTCC) technology has become one of the main forms of manufacturing electronic devices. However, a majority of microwave dielectric ceramics are not suitable as LTCC materials due to their high sintering temperatures. Developing novel LTCC materials with good microwave dielectric properties is extremely urgent. In this paper, an LiF sintering aid was added to Li₂Ti_0.8(Co_1/3Nb_2/3)_0.2O₃ (LTCN) ceramics to explore new LTCC materials. The sintering behavior, microstructure and microwave dielectric properties of LTCN + x wt% LiF ceramics were investigated in detail. The results indicated that the addition of LiF increased the degree of disorder in the LTCN matrix, transforming it from a monoclinic to a cubic crystal system. The ceramics exhibited relatively dense and homogeneous microstructures at the sintering temperature of 950 °C as the LiF doping amount was not less than 2 wt%. By LiF doping, the quality factor (Q × f) value was significantly enhanced due to the improved microstructure. Meanwhile, the temperature coefficient of resonant frequency (τ_f) of LTCN ceramics was successfully regulated to the near zero value owing to the negative τ_f characteristic of LiF. Excellent microwave dielectric properties of dielectric constant (ε_r) = 19.01, Q × f = 144,890 GHz, τ_f = −1.52 ppm/°C were obtained when the sample doped 3 wt% LiF was sintered at 950 °C for 3 h. Furthermore, the good chemical compatibility of the LTCN-3 wt% LiF ceramic with silver electrodes suggested that the ceramic was a potential material for LTCC applications. Full article

Silver paste is widely used for low-temperature co-fired ceramic (LTCC) electrodes. In this work, a kind of LTCC silver paste for fine-line screen-printing was developed by considering the effect of the organic vehicle on rheological behavior and screen-printing properties. A step-by-step volatilization mode was applied to screen the mixed organic solvent of α-terpineol, 2-(2-butoxyethoxy) ethyl acetate (BCA) and dibutyl phthalate (DBP). The α-terpineol:BCA:DBP ratio of 5:2:3 is selected by considering the volatility, viscosity, and pseudoplasticity of the organic vehicle. Both viscosity and pseudoplasticity of shear-thinning increase with the increase of ethyl cellulose (EC) organic binder content. Three interval thixotropy test (3ITT) was conducted to discuss the thixotropy of silver paste. The minimum printing line width of 13.27 µm is obtained using silver paste with 10 wt% EC, confirming that the homemade paste has good printability. Full article

The design, fabrication and functional evaluation of the radio-frequency dielectric heating of liquids in an LTCC-based ceramic microfluidic system are described and discussed. The device, which relies on the dielectric heating of liquids, was fabricated using a low temperature co-fired ceramic (LTCC) technology. A multilayered ceramic structure with integrated electrodes, buried channels and cavities in micro and millimetre scales was fabricated. The structure with the dimensions of 35 mm × 22 mm × 2.4 mm includes a buried cavity with a diameter of 17.3 mm and a volume of 0.3 mL. The top and bottom faces of the cavity consist of silver/palladium electrodes protected with 100 μm thick layers of LTCC. The power, used to heat a polar liquid (water) in the cavity with the volume of 0.3 mL, ranges from 5 to 40 W. This novel application of RF dielectric heating could enable the miniaturization of microfluidic systems in many applications. The working principle of such a device and its efficiency are demonstrated using water as the heated medium. Full article

This work presents a comparison of values of the contact resistivity of silicon solar cells obtained using the following methods: the transmission line model method (TLM) and the potential difference method (PD). Investigations were performed with two independent scientific units. The samples were manufactured with silver front electrodes. The co-firing process was performed in an infrared belt furnace in a temperature range of 840 to 960 °C. The electrical properties of a batch of solar cells fabricated in two cycles were investigated. This work focuses on the different metallisation temperatures of co-firing solar cells and measurements were carried out using the methods mentioned. In the TLM and PD methods, the same calculation formulae were used. Moreover, solar cell parameters measured with these methods had the same, similar, or sometimes different but strongly correlated values. Based on an analysis of the selected databases, this article diagnoses the recent and current state of knowledge regarding the employment of the TLM and PD methods and the available hardware base. These methods are of interest to various research centres, groups of specialists dealing with the optimisation of the electrical properties of silicon photovoltaic cells, and designers of measuring instruments. Full article

This work presents comparison results of the selected electrical parameters of silicon solar cells manufactured with silver front electrodes which were co-fired in an infrared belt furnace in the temperature range of 840–960 °C. The commercial paste (PV19B) was used for the metallization process. Electrical properties of a batch of solar cells fabricated in one cycle were investigated. Three methods were used, including measurement of the current-voltage characteristics (I-V), measurement of contacts’ resistivity using the transmission Line model method (TLM), and measurement of contacts’ resistivity using the potential difference method (PD). This work is focused on both the different metallization temperatures of co-firing of solar cells and measurements using the above-mentioned methods. It is shown that the solar cell parameters measured with three methods have different, but strongly correlated values. Moreover, the comparative analysis was performed of the investigations of the same photovoltaic solar cells using both the TLM method and independent research stands (including one non-commercial and two commercial ones) at three different scientific units. In the PD and TLM methods, the same calculation formulae are used. It can be stated, comparing methods I-V, PD, and TLM, that for each, different parameters are determined to assess the electrical properties of the solar cell. Full article

Electrode material for low-temperature co-fired diopside glass-ceramic used for microwave dielectrics was investigated in the present work. Diffusion of silver from the electrode to diopside glass-ceramics degrades the performance of the microwave dielectrics. Two approaches were adopted to resolve the problem of silver diffusion. Firstly, silicon-oxide (SiO₂) powder was employed and secondly crystalline phases were chosen to modify the sintering behavior and inhibit silver ions diffusion. Nanoscale amorphous SiO₂ powder turns to the quartz phase uniformly in dielectric material during the sintering process, and prevents the silver from diffusion. The chosen crystalline phase mixing into the glass-ceramics enhances crystallinity of the material and inhibits silver diffusion as well. The result provides a method to decrease the diffusivity of silver ions by adding the appropriate amount of SiO₂ and appropriate crystalline ceramics in diopside glass-ceramic dielectric materials. Finally, we used IEEE 802.11a 5.8 GHz as target specification to manufacture LTCC antenna and the results show that a good broadband antenna was made using CaMgSi₂O₆ with 4 wt % silicon oxide. Full article

Although lead-free piezoelectric ceramics have been extensively studied, many problems must still be overcome before they are suitable for practical use. One of the main problems is fabricating a multilayer structure, and one solution attracting growing interest is the use of lead-free multilayer piezoelectric ceramics. The paper reviews work that has been done by the authors on lead-free alkali niobate-based multilayer piezoelectric ceramics co-fired with nickel inner electrodes. Nickel inner electrodes have many advantages, such as high electromigration resistance, high interfacial strength with ceramics, and greater cost effectiveness than silver palladium inner electrodes. However, widely used lead zirconate titanate-based ceramics cannot be co-fired with nickel inner electrodes, and silver palladium inner electrodes are usually used for lead zirconate titanate-based piezoelectric ceramics. A possible alternative is lead-free ceramics co-fired with nickel inner electrodes. We have thus been developing lead-free alkali niobate-based multilayer ceramics co-fired with nickel inner electrodes. The normalized electric-field-induced thickness strain (S_max/E_max) of a representative alkali niobate-based multilayer ceramic structure with nickel inner electrodes was 360 pm/V, where S_max denotes the maximum strain and E_max denotes the maximum electric field. This value is about half that for the lead zirconate titanate-based ceramics that are widely used. However, a comparable value can be obtained by stacking more ceramic layers with smaller thicknesses. In the paper, the compositional design and process used to co-fire lead-free ceramics with nickel inner electrodes are introduced, and their piezoelectric properties and reliabilities are shown. Recent advances are introduced, and future development is discussed. Full article