Ceramic Thick Films Research Articles

Room temperature deposition of freestanding BaTiO3 films: temperature-induced irreversible structural and chemical relaxation

The room temperature aerosol deposition method is especially promising for the rapid deposition of ceramic thick films, making it interesting for functional components in energy, mobility, and telecommunications applications. Despite this, a number of challenges remain, such as an enhanced electrical conductivity and internal residual stresses in as-deposited films. In this work, a novel technique that integrates a sacrificial water-soluble buffer layer was used to fabricate freestanding ceramic thick films, which allows for direct observation of the film without influence of the substrate or prior thermal treatment. Here, the temperature-dependent chemical and structural relaxation phenomena in freestanding BaTiO3 films were directly investigated by characterizing the thermal expansion properties and temperature-dependent crystal structure as a function of oxygen partial pressure, where a clear nonlinear, hysteretic contraction was observed during heating, which is understood to be influenced by lattice defects. As such, aliovalent doping and atmosphere-dependent annealing experiments were used to demonstrate the influence of local chemical redistribution and oxygen vacancies on the thermal expansion, leading to insight into the origin of the high room temperature conductivity of as-deposited films as well as greater insight into the influence of the induced chemical, structural, and microstructural changes in room temperature deposited functional ceramic thick films.Graphical abstract

Characterization of Li₂MoO₄/BaTiO₃ All-Ceramic Films on Organic Substrate Printed Capacitors at 45 MHz–10 GHz

This article presents novel all-ceramic composite films used as a screen-printed capacitors on polymer surface and their characterization at 45-MHz to 10-GHz frequency range. All-ceramic composite paste is based on lithium molybdate (Li₂MoO₄), barium titanate (BaTiO₃), and water manufactured by the room temperature fabrication (RTF) method. For the determination of the permittivity and the loss tangent of the materials, ceramic thick films are printed on the top of an interdigital-shaped microwave capacitors using pastes with 0, 10, and 20 vol.&#x0025; of BaTiO₃ filler in Li₂MoO₄ followed by a drying process at 120 &#x00B0;C. The electrical properties of the capacitors, capacitance, and quality value are derived from measured <inline-formula> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula>-parameter results, whereas the electrical properties of the ceramic thick-film materials, real, and imaginary values of permittivity are derived from the measured results through computer simulations. The electrical properties of the ceramic material, such as moderate permittivity and moderately low-loss tangent, could be adjusted by changing the volume fraction of the BaTiO₃ filler to match the demands of different areas of applications. The obtained results are verified with five samples of each ceramic composition. The results show the capacitance values of 0.30 pF for an uncoated capacitor and 0.55, 0.67, and 0.95 pF with coatings of Li₂MoO₄ with 0, 10, and 20 vol.&#x0025; of BaTiO₃ composites, respectively, at 2.5-GHz frequency. The calculated relative permittivity (<inline-formula> <tex-math notation="LaTeX">$\varepsilon _{r}$ </tex-math></inline-formula>) values for the same materials are 3.70, 5.23, and 6.43, and loss tangent values are 0.035, 0.027, and 0.036 at 2.5 GHz. These novel all-ceramic capacitor composite materials are applicable for the RF components used in telecommunication applications in the frequency range of 45 MHz&#x2013;10 GHz, thus widening the technology roadmap in terms of material choices for different applications, especially high thermal resistant materials.

Multifunctional energy storage and piezoelectric properties of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 thick films on stainless-steel substrates

The miniaturization of electronic devices and power systems requires the fabrication of functional components in the form of micrometer-sized thick films. A major challenge is the integration of functional ceramics with metals, which are considered incompatible with high-temperature ceramic processing. To overcome the integration barrier, an aerosol deposition (AD) spray-coating method based on room temperature deposition can be used. By employing the AD method, we were able to deposit relaxor-ferroelectric 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 ceramic thick films on low-cost stainless-steel substrates. The as-deposited films were dense, with ∼97% of the theoretical density. Moreover, the post-deposition annealing at 500 °C did not result in any microstructural changes. Compared to the as-deposited films, the annealed films exhibit improved energy storage and electromechanical properties. The annealed thick films achieve a recoverable energy density of 15.1 J⋅cm−3 at an electric field of 1350 kV⋅cm−1 and an electric-field cycling stability of 5 million cycles. A piezoelectric response was detected through the entire film thickness by piezoelectric force microscopy. Macroscopic displacement measurements revealed a maximum relative strain of 0.38% at 1000 kV⋅cm−1, corresponding to inverse effective piezoelectric coefficient of ∼40 pm⋅V−1. In this study, we overcame the integration challenges and demonstrated the multifunctionalization of future ceramic-metal structures, as the deposited thick films on stainless steel exhibit energy storage capability and piezoelectric properties.

Large energy storage density and electrocaloric strength of Pb0.97La0.02(Zr0.46-xSn0.54Tix)O3 antiferroelectric thick film ceramics

Pb0.97La0.02(Zr0.46-xSn0.54Tix)O3 (PLZST, x = 0.04, 0.06, 0.08, 0.15, and 0.18) antiferroelectric thick film ceramics were fabricated via a tape-casting approach. The energy storage performance and electrocaloric effect (ECE) were investigated in terms of the measurements on the hysteresis loops and Maxwell relation. The maximum value of energy storage density of 5.2 J/cm3 and efficiency of 78.2% were procured at 600 kV/cm in Pb0.97La0.02(Zr0.42Sn0.54Ti0.04)O3 thick film ceramics at room temperature. In addition, the ECE was indirectly calculated using the Maxwell relation and the polarizations extracted from the P-E loops as a function of temperature and electric field, an adiabatic temperature change of ΔT = 2.47 °C was procured in Pb0.97La0.02(Zr0.42Sn0.54Ti0.04)O3 thick film ceramics at 500 kV/cm, corresponding to the calculated electrocaloric strength of 0.48 K(MV/m)−1. These results indicate that the PLZST thick film ceramics are promising for practical applications in high-power energy storage capacitors and solid-state refrigeration devices.

Cu-Mn Co-doped NiFe2O4 based thick ceramic film as negative temperature coefficient thermistors

NTC (Negative Temperature Coefficient) thermistors are widely used as temperature sensors in industrial and medical applications due to their high-temperature sensitivity, durability, and low cost. Generally, NTC thermistors are made from spinel structured ceramics formed by transition metal oxides with the general formula AB2O4. One of the spinel structured ceramics that can be made for NTC thermistors is NiFe2O4 nanoparticles. This work aimed to prepare Cu-Mn co-doped NiFe2O4 based thick ceramic film using Jarosite mineral as a precursor. The synthesis method used was a simple coprecipitation method, while the technique used in making a thick ceramic film was a simple screen printing technique. The sintering temperatures used were 1000 °C, 1100 °C, and 1200 °C. Based on x-ray diffraction analysis, the thick films consist of spinel phase, hematite phase, and some unidentified phase. The constant thermistor values (B) for thick films obtained with 1000, 1100, and 1200 °C sintering temperatures were 4740 K, 5669 K, and 5731 K, respectively. These results showed that all obtained thick films had passed the minimum value in market needs (B ≥2000 K).

Effect of solid contents on the electrical properties of Co2.77Mn1.71Fe1.10Zn0.42O8 ceramic prepared by slurry spin coating technique

A series of negative temperature coefficient (NTC) thick-film ceramics based on Co2.77Mn1.71Fe1.10Zn0.42O8 (CMFZ) were successful prepared using a slurry spin coating technique. The high density and stable B25/50 constant in the range of 3829–3862 K of CMFZ thick films were obtained. The feasibility of preparing CMFZ thick films by spin coating is proved. It is confirmed that the microstructure and electrical properties of films are sensitive to the solid content in pastes. A smoother and denser surface morphology and relatively high electrical stability is obtained in 70 wt% solid content with the resistance drift rate of 19.4%. The resistance drift rate of all samples is found to be less than 1% per 100 h after pre-aging at 125 °C for 400 h. Compared to the traditional screen-printing method, spin coating simplifies the process steps and reduces some variables that could affect the quality of the thick film. These results clearly indicate that the spin coating technique is a potential and competitive method in the production of NTC thick film ceramic.

1MW-Class Solid Oxide Electrolyser System Prototype for Low-Cost Green Hydrogen

Ceres has developed a novel and highly differentiated SteelCell™ solid oxide fuel cell technology based upon the use of thick-film ceramics deposited upon a ferritic stainless-steel substrate, using doped ceria as the predominant oxygen-ion conducting ceramic within the cell. The use of ceria allows operation of the SteelCell at lower temperatures (500 - 620 °C) than conventional SOFCs, and the use of a metal support allows much greater mechanical robustness and lower production cost than is typically the case with a planar ceramic SOFC, whilst maintaining the high volumetric power density typical of planar SOFCs.Ceres Power are now qualifying their SteelCell™ technology for use in steam electrolysis operation with encouraging results. Tests suggest that functional electrochemical and physical processes of the SteelCell are equally efficient in SOFC and SOEC mode meaning there is no major difference in the area specific resistance and degradation within the nominal operating space.As a next step, the development of a 1MW-class Solid Oxide Electrolysis (SOEL) system is proposed that offers a path to green hydrogen production costs of <$2/kgH2 with equally compelling capital equipment costs enabled by the SteelCell technology. One of the clear advantages of solid oxide electrolysis systems is the ability to thermally integrate with industrial processes such as steel, ammonia and e-fuels production. Integration with existing low pressure “waste” steam feeds available at industrial plants combined with available high grade heat streams may enable system efficiencies of greater than 90% to be achieved. A study of predicted system efficiencies and associated techno-economics of green hydrogen production under various industrial use cases is presented.The first-of-a-kind 1MW-class Solid Oxide Electrolysis system under consideration will be packaged within a 40ft ISO shipping container and is expected to produce approximately 600 to 800kg of green hydrogen per day. The system will be made up of a number of Electrolysis Cell Modules (ECM). Each ECM will contain an array of Ceres’ standard Gen1B stacks along with hot balance of plant components such as heat exchangers and heaters. This modular approach allows each module to be constructed and tested prior to installation at the demonstration site. It also allows for a high degree of fault tolerance and redundancy that is particularly valuable for prototype systems. Furthermore, it also enables a distributed supply chain to be developed for various elements up and down the system structure.Finally, a roadmap to the first commercial SOEL systems is presented setting out predicted system CapEx costs, hydrogen production costs and possible arrangements for systems in the 100+ MW range.

The enhancement of ethanol gas sensors response based on calcium and zinc co-doped LaFeO3/Fe2O3 thick film ceramics utilizing yarosite minerals extraction as Fe2O3 precursor

A gas sensor is a renewed interest of research which has been developed to make a device that can be detected the harmful gases and applied in the several fields of industries. In this paper, we report the modified of gas sensor based thick film ceramic LaFeO3/Fe2O3 by added calcium and zinc co-doping prepared by screen-printed technique. In this work, yarosite mineral was utilized as Fe2O3 precursor. It aims to take the advantages of abundance natural resources in Indonesia to save a cost in gas sensor fabrication. Then, x-ray diffraction (XRD), scanning electron microscopy (SEM) and electrical properties characterization were applied to the calcium and zinc co-doped LaFeO3/Fe2O3-based thick film ceramics. It is obtained that the crystal structures were cubic with crystallite size at about 51.19 nm and 48.17 nm. SEM images informed that calcium and zinc co-doped caused the larger pores of LaFeO3/Fe2O3. It indicates that the gas sensors shows a response to the ethanol gases. Lastly, calcium and zinc co-doped can be a potential candidate to enhance the highly performance of gas sensors. Moreover, yarosite mineral also can be used to develop the future perspectives of ethanol gas sensors.

Granule spray process for fabrication of adherent, low thermal conductivity ceramic coatings

This study proposes an effective strategy to fabricate ceramic thick films with controllable porosity but strong mechanical adhesion. The technique uses pre-heat-treated granules for a dry spray coating process, granule spray in vacuum. For proof-of-concept, Y2O3 spherical granules were prepared and subsequently pre-heat-treated at various temperatures to control their strength. During film deposition, hard granules (i.e., pre-heated at 1400 °C) caused damage to the substrate and pre-deposited film, owing to a strong hammering effect, which lead to limited film growth (1–2 μm). Contrarily, soft granules (i.e., pre-heated below 800 °C) produced a powder compact with low adhesion, resulting in delamination of some parts. This is attributed to the reduction in kinetic energy caused by the elastic cushioning effect during deposition. Regarding the granules with appropriate strength (i.e., pre-heated at 1000 °C), relatively porous (relative density: 74%) but mechanically well-adhering (adhesion strength: 41 MPa) thick films (~60 μm) were successfully coated on Al substrates. These films exhibited four times higher adhesion strength than those prepared with Y2O3 coatings using atmospheric plasma spraying. The films showed low thermal conductivities (~0.76 W/m·K at R.T.), suggesting potential application of our approach in the field of thermal insulation.

Effect of Zr:Sn ratio in the PBLZST ceramic thick films on the energy storage characteristics

Pb0.91Ba0.06La0.02(Zr0.95−xSnxTi0.05)O3 (PBLZST, x = 0.325, 0.35, 0.375, 0.4) thick films are prepared by solid-state reaction method and flow-casting method. Trace Ba2+ content is introduced to PLZST which is effective in narrowing the hysteresis loop, lowering the Curie temperature point, and improving the fatigue characteristics. Besides that, Zr:Sn ratios are adjusted to study its influence on the material’s energy storage characteristics. PBLZST ceramics with different Zr:Sn ratios are all in tetragonal perovskite structure. The increase of Sn4+ content promotes miniaturization of crystal grain and contributes to stability of antiferroelectric phase, together with enhances the phase transition field strength and breakdown field strength of PBLZST ceramics. The PBLZST ceramic has high energy storage efficiency, which is more than 80%. The maximum effective energy storage density of PBLZST ceramics at 1.94 J/cm3 is obtained when x = 0.35, and their energy storage efficiency is 81.9%, which confirms that they are the potential materials in the pulse energy storage components.

Large Energy Storage Density and Electrocaloric Strength of Pb &lt;sub&gt;0.97&lt;/sub&gt;La &lt;sub&gt;0.02&lt;/sub&gt;(Zr &lt;sub&gt;0.46-x&lt;/sub&gt;Sn &lt;sub&gt;0.54&lt;/sub&gt;Ti &lt;sub&gt;x&lt;/sub&gt;)O &lt;sub&gt;3&lt;/sub&gt; Antiferroelectric Thick Film Ceramics

Pb0.97La0.02(Zr0.46-xSn0.54Tix)O3 (PLZST, x=0.04, 0.06, 0.08, 0.15, and 0.18) antiferroelectric thick film ceramics were fabricated via a tape-casting approach. The energy storage performance and electrocaloric effect were investigated in terms of the measurements on the hysteresis loops and Maxwell relation. The maximum value of energy storage density of 5.2 J/cm3 and efficiency of 78.2 % were procured at 600 kV/cm in Pb0.97La0.02(Zr0.42-xSn0.54Ti0.04)O3 thick film ceramics at room temperature. In addition, the ECE was indirectly calculated using the Maxwell relation and the P-E loops as a function of temperature and electric field, a reversible adiabatic temperature change of ΔT=2.47 °C was presented in Pb0.97La0.02(Zr0.42-xSn0.54Ti0.04)O3 thick film ceramics at 500 kV/cm, corresponding to the calculated electrocaloric strength of 0.48 K(MV/m)-1. These results indicate that the PLZST thick film ceramics are promising for practical applications in high-power energy storage capacitors and solid-state refrigeration devices.

Piezoelectric Thick Film Deposition via Powder/Granule Spray in Vacuum: A Review

Conventional thin-film processing techniques remain inadequate for obtaining superior dense ceramic thick films. The incompatibility of ceramic films prepared via other methods, such as screen printing, spin coating, and sputtering, is a major obstacle in the fabrication of thick film-based ceramic electronic components. The granule spray in vacuum (GSV) processes and aerosol deposition (AD) are important coating approaches for forming dense ceramic thick films featuring nanoscale crystallite structures at room temperature, which offer excellent material properties and facilitate cost-effective production. AD ceramic coatings require the acceleration of solid-state submicron ceramic particles via gas streams with a velocity of a few hundred meters per second, which are then wedged onto a substrate. This process is economical and particularly useful for the fabrication of piezoelectric thick film-based microactuators, energy harvesters, sensors, and optoelectronic devices. More recently, the GSV technique was improved to achieve more uniform and homogeneous film deposition after AD. This review article presents a detailed overview of the AD and GSV processes for piezoelectric thick films in terms of recent scientific and technological applications.

Dense, nano-grained, multi-phase ceramic coatings by dry aerosol deposition of lunar regolith simulant

Dry Aerosol Deposition (DAD) is a ceramic coating process with the ability to build films and low profile 3D structures layer by layer and is therefore a promising additive manufacturing technique. DAD is unique because it uses kinetic energy rather than thermal energy for densification, and the result is a nearly theoretically dense, nano-crystalline ceramic. The main objectives of this work were to demonstrate the fabrication of adherent ceramic thick films onto a variety of substrates using lunar regolith simulant as feedstock, and to investigate the compositional relationships between feedstock and resultant films. Thick films were successfully deposited onto glass, steel and polyimide substrates via DAD. Using a sequential two-step deposition, films up to (but not limited to) 25 μm thickness were deposited onto steel. Surface roughness increased with thickness and with some influence from substrate material. Utilizing the DAD process, a very heterogeneous mixture of silicate and titanate mineral phases was transformed in a single step to a fully dense, nano-grained coating with spatially homogeneous composition at the micro-scale. The final composition of the coatings was found to deviate slightly from the feedstock powder, becoming richer in ilmenite (FeTiO3) and poorer in plagioclase (feldspar) content. This work demonstrates the potential of DAD for in-space manufacturing and lunar In Situ Resource Utilization.

State-of-the-Art and Practical Guide to Ultrasonic Transducers for Harsh Environments Including Temperatures above 2120 °F (1000 °C) and Neutron Flux above 1013 n/cm2.

In field applications currently used for health monitoring and nondestructive testing, ultrasonic transducers primarily employ PZT5-H as the piezoelectric element for ultrasound transmission and detection. This material has a Curie–Weiss temperature that limits its use to about 210 °C. Some industrial applications require much higher temperatures, i.e., 1000–1200 °C and possible nuclear radiation up to 1020 n/cm2 when performance is required in a reactor environment. The goal of this paper is the survey and review of piezoelectric elements for use in harsh environments for the ultimate purpose for structural health monitoring (SHM), non-destructive evaluation (NDE) and material characterization (NDMC). The survey comprises the following categories: 1. High-temperature applications with single crystals, thick-film ceramics, and composite ceramics, 2. Radiation-tolerant materials, and 3. Spray-on transducers for harsh-environment applications. In each category the known characteristics are listed, and examples are given of performance in harsh environments. Highlighting some examples, the performance of single-crystal lithium niobate wafers is demonstrated up to 1100 °C. The wafers with the C-direction normal to the wafer plane were mounted on steel cylinders with high-temperature Sauereisen and silver paste wire mountings and tested in air. In another example, the practical use in harsh radiation environments aluminum nitride (AlN) was found to be a good candidate operating well in two different nuclear reactors. The radiation hardness of AlN was evident from the unaltered piezoelectric coefficient after a fast and thermal neutron exposure in a nuclear reactor core (thermal flux = 2.12 × 1013 ncm−2; fast flux 2 (>1.0 MeV) = 4.05 × 1013 ncm−2; gamma dose rate: 1 × 109 r/h; temperature: 400–500 °C). Additionally, some of the high-temperature transducers are shown to be capable of mounting without requiring coupling material. Pulse-echo signal amplitudes (peak-to-peak) for the first two reflections as a function of the temperature for lithium niobate thick-film, spray-on transducers were observed to temperatures of about 900 °C. Guided-wave send-and-receive operation in the 2–4 MHz range was demonstrated on 2–3 mm thick Aluminum (6061) structures for possible field deployable applications where standard ultrasonic coupling media do not survive because of the harsh environment. This approach would benefit steam generators and steam pipes where temperatures are above 210 °C. In summary, there are several promising approaches to ultrasonic transducers for harsh environments and this paper presents a survey based on literature searches and in-house laboratory observations.

Fabrication of porous thick films using room‐temperature aerosol deposition

AbstractA novel technique for the rapid room‐temperature deposition of porous ceramic, glass, or metal thick films using the aerosol deposition (AD) method is presented. The process is based on the co‐deposition of the desired film material and a second water‐soluble constituent, resulting in a ceramic‐ceramic composite. Following the subsequent removal of water‐soluble end member, a network of pores is retained. To demonstrate the process, porous BaTiO3 thick films were fabricated through co‐deposition with NaCl. Microstructural images show the clear development of a porous structure, which was found to enhance the dielectric properties over dense thick films, possibly related to the lower extent of internal residual stress. This simple but highly effective porous structure fabrication can be applied to any film and substrate material stable in water and is promising for the application of AD‐processed films in gas sensors, solid oxide fuel cells, and humidity sensors.

Preparation and Characterization of Large Area Li-NASICON Electrolyte Thick Films

The preparation of solid electrolyte ceramic membranes is the object of intense study for its fundamental parts in the development of all solid-state batteries and improved battery separators. In this work, the procurement of large area solid electrolyte ceramic thick film membranes of the Li-NASICON Li1.3Al0.3Ti1.7(PO4)3 (LATP) composition is attempted. Through the use of LATP powders from a sol–gel reaction, a slurry is formulated and tape casted. The green tapes are sintered using two sintering times. In both cases, ceramic thick films of a 5.5 × 5.5 cm2 area and ≈250 µm average thickness were obtained. The characterization indicated almost pure phase samples with a bi-modal microstructure composed of large and smaller grains, being larger for longer sintering time. The samples are porous and brittle, presenting very high “bulk” conductivity but lower total direct current (DC) one, as compared with the commercial Li-NASICON (OHARA) thick films with a similar area. The larger the grains, the poorer the total conductivity and the mechanical properties of the thick-films. The formation of poorly adhering grain boundaries as the grain size grows is responsible for the worsened properties. A better control of the microstructure is mandatory.

Fabrication and Characterization of Fine-Grained Nasicon-Structured Li Electrolyte for Solid State Batteries Applications

Rechargeable batteries using inorganic ionic conductors as solid electrolytes have been proposed over decades. Due to their improved safety features, solid state batteries have received great attention recently. Among several inorganic ionic conductors, NASICON-structured Li1+xAlxTi2-x(PO4)3 (LATP) show excellent ionic conduction and adequate structural stability when used as the solid electrolyte for Li battery applications. However, the physical properties of solid electrolyte may be affected by their chemical composition and processing parameters. Thus, the objective of this study is (i) to investigate the effect of grain size on the electrical properties, (ii) to lower interface polarization of layered oxide cathode/electrolyte, (iii) to examine the effect of microstructure variation on cathode/solid electrolyte performance. In this study, the ceramic self-standing thick films of Li- NASICON with composition Li1.3Ti1.7Al0.3(PO4)3 by tape casting were prepared. A full cell using layered oxide/graphite (or Li metal) as the cathode/anode separated by LATP were assembled and tested A complete characterization of the samples including structural, microstructural, impedance as well as the electrochemical testing were conducted. Due to dependence of grain-size on ionic conduction, more discussion will focus on the contribution of both the grain boundary and the "bulk" conductivity. Microstructure will be varied by creation of different pore size and porosity in order to search for better electrode configuration.

Energy storage BaZr0.2Ti0.8O3 bilayer relaxor ferroelectric ceramic thick films with high discharging efficiency and fatigue resistance

Excellent electric energy discharging efficiency and fatigue resistance are two critical factors in high energy storage capacitor for electronic device and high-power system with fast charging-discharging speed. Here, we report on designing and preparing the thick films of BaZr0.2Ti0.8O3 (BZT20) bilayer ceramics (BLCs) (∼40 μm in thickness) using a tape casting method. In this ABO3-structured perovskite ceramics, the B position of Ti was occupied by 20 mol% Zr atoms, which leads to order-disordering and random fields in the single phase with both the tetragonal (space group P4mm) and rhombohedral (space group m-3m). And therefore, the relaxors possess a heterogeneous polar state at the nanoscale and their long-range domains are disrupted. Consequently, a non-hysteretic arc-shaped unipolar polarization-electric frield loop (P-E loop) in which the curve obtained under a considerable high electric field of 80 MV m−1 and the curve under depolarization are overlaped. As such, a large energy storage density (Ue) of ∼6.2 J cm−3 with the discharging efficiency of ∼98% and a considerable fatigue resistance over 22 k cycles at a wide temperature range from 253 to 393 K (−20 °C–120 °C) are obtained. The attractive electric performance of this BLCs films demonstrates that this sort of relaxor ceramics is one of promising materials for capacitors with little calorigenic electronic power areas.

Investigation towards the optimum of power capability, ageing stability and costs effectiveness on thick film resistor pastes for AlN ceramics

Abstract The focus of this work was the optimization of a 10 Ω/□ thick film resistor (TFR) paste composition to obtain increased power capability, aging stability and minimum use of ruthenium oxide for cost savings without changing the defined narrow sheet resistance (R□) and temperature coefficient of resistance (TCR) specifications. In times of highly fluctuating precious metal costs, the use of a minimum of the precious metal ruthenium respectively ruthenium dioxide is one essential part for cost-effectiveness. The thick film paste formulation consists of the electrically conducting phase ruthenium dioxide, a lead-free glass phase and two inorganic additives for tuning thermo-mechanical and electrical properties of the formed films. A phthalate free organic vehicle with ethyl cellulose polymer was used to formulate a screen printable ceramic thick film paste. For this paper, RuO2 powders with various specific surface area values (BET) were prepared by thermal annealing of a precipitated fine ruthenium dioxide powder. All other solid and liquid components of the paste were the same as used for IKTS 10 Ω/□ TFR paste FK9611 for AlN substrates. Furthermore, the content of ruthenium dioxide in the paste compositions was changed systematically around an assumed target content to achieve the desired sheet resistivity. Concurrent to the variation of the ruthenium dioxide content the inorganic additives had to be adapted too. The influence of the variations of raw material and paste composition on the film properties were investigated by screen printing 24 resistors of 2 mm × 1 mm dimension on an 1” × 1” AlN substrate, firing at 850 °C for 10 minutes in air atmosphere and subsequently measuring R□, TCR, the stability of resistance ΔR/R0 effected by artificial aging of the resistors (stored 100 up to 1000 hours @ 200°C) and the maximum rated power dissipation (MRPD) as well as short term overload voltage (STOL). The results are discussed in regard to find an optimum between all demands of the most important electrical film properties.

Fabrication and Characterization of Thick Film Ceramics La0,9Ca0,1FeO3 for Ethanol Gas Sensor using Extraction of Fe2O3 from Yarosite Mineral

Fabrication of La0,9Ca0,1FeO3 thick film ceramics using Fe2O3 powder extracted from yarosite mineral as ethanol gas sensor has been successfully performed. Fe2O3 powder extracted from yarosite mineral as the basic material in this research can increase the added value yarosite mineral. Fe2O3 powder and 10% mol of CaO dissolved in HCl were mixed with LaCl3.7H2O powder dissolved in aquades.The solution of Fe2O3, LaCl3.7H2O and CaO mixed and then precipitate using NH4OH. The La0,9Ca0,1FeO3 precipitate was calcined at temperature 8000C for 2 hours to produce La0,9Ca0,1FeO3 powder. La0,9Ca0,1FeO3 powder was crushed and mixed with Organic Vehicle to produce a La0,9Ca0,1FeO3 paste. Using the screen printing technique, the La0,9Ca0,1FeO3 paste is coated on the alumina substrate and then fired at 600°C for 2 hours to produce the thick film ceramic La0,9Ca0,1FeO3. Based on XRD and SEM characterization data, the thick film ceramics La0,9Ca0,1FeO3 were made even though some of Fe2O3 did not react and the grain size is almost uniform, and there are many pores. Measurement of electrical characteristics shows a good response to the presence of ethanol gas, has high electrical sensitivity value and low optimum working temperature that is in the range 290°C - 295°C.