Ferrite Thick Films Research Articles

Effect of Reheating Temperatures on Hot Ductility and Precipitation Behavior of Low‐Carbon Steels

The influence of reheating temperatures on hot ductility is investigated in two Ni‐, Mo‐, and Cu‐containing low‐carbon steels. The effects of solution treatment conditions at 1623, 1673 K, and remelting at 1803 K on the reduction in area (RA) are analyzed. The results show an RA trough in the range of 973–1173 K in all experimental conditions. At 973 K, which is close to the Ae3 temperature of both steel grades, ductility drop is caused by the formation of the thin ferrite film at the prior austenite grain boundary. Higher RA values are achieved after reheating to 1623 K, mainly due to smaller austenite grain size by the action of preformed precipitation throughout the matrix. In contrast, increased reheating temperatures result in relatively poor RA values because of the large austenite grain size due to the dissolution of preformed precipitate and reprecipitation at the grain boundaries during cooling. A comparison between two steel grades shows that better ductility at 973 K is achieved in low Ni‐containing steel due to the relatively thick ferrite film. The effects of alloy composition and preformed precipitate's existence on hot ductility are further discussed based on the matrix strengthening and reprecipitation behavior.

Enhanced H2S gas sensing performance of Ca-doped Bismuth Ferrite thick films

In the present work, gas sensing properties of Calcium-doped Bismuth Ferrite (BFO) nano-particulate films have been investigated as a function of doping concentration, operating temperature and nature of the exposure gases. Pure Bismuth ferrite films were found to be sensitive towards H2S gas at 350 °C. With increase in calcium concentration, besides an increase in sensor response, from ∼4.5 in BFO to ∼226 in Bi0·7Ca0·3FeO3 on exposure to 50 ppm of H2S, a non-ideal p-type behavior is observed in response curves. Such a large enhancement has not been observed earlier in a p-type semiconductor. In BFO and Bi0·9Ca0·1FeO3, resistance of films is observed to increase in accordance to p-type behavior, followed by a small decrease before saturation in gas ambience. In samples with higher calcium content, on exposure to gas, resistance of the sample is observed to increase initially followed by a decrease in resistance while still in gas ambience (saturation in gas ambience is not at all observed). In order to investigate the reason for (i) the large enhancement in sensor response usually not observed in a p-type sensor, and (ii) origin of non-ideal p-type behavior, X-ray photoelectron spectroscopy analysis of Bi0·7Ca0·3FeO3 films was carried out, after gas exposure. Based on analysis of XPS results, an additional sensing mechanism involving chemical reaction between the cations of sensing material and H2S, was found; which could satisfactorily explain the non-ideal behavior as well as enhancement in sensor reponse.

Mn doped Ni-Zn ferrite thick film as a highly selective and sensitive gas sensor for Cl2 gas with quick response and recovery time

The Ni0.7-xMnxZn0.3Fe2O4 (x = 0.1–0.4) ferrites were characterized by X-ray diffraction, Transmission electron microscopy, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy. The thick films of these ferrites were fabricated on a glass substrate to use as a Cl2 sensor. The ferrite thick film with composition x = 0.3 showed a selectively high response towards Cl2 gas at an operating temperature of 100 °C. The response varied from 115 to 212% for 20–300 ppm of Cl2 gas. The response time was found to be within 10 s while the recovery time was less than 15 s. The results were quite reproducible thus making this material a good sensor for Cl2 gas.

Selective sensing of oxidizing gases on Co-Ni-Zn ferrite: Mechanism and response characteristics

Studies demonstrate the selective gas sensing characteristics of Co-Ni-Zn ferrite thick film towards oxidizing gases over reducing gases. The Co0.3Ni0.3Zn0.4Fe2O4 ferrite was prepared by combustion method and characterized for its phase purity, nanodimension and valence state by analytical techniques, includes X-ray diffraction, Raman spectroscopy, Transmission Electron Microscopy and X-ray photoelectron spectroscopy, respectively. The Co0.3Ni0.3Zn0.4Fe2O4 gas sensor was fabricated in the form of thick film by screen printing method, and the response of film towards selected oxidizing gases and the reducing gases were investigated. It was found that Co0.3Ni0.3Zn0.4Fe2O4 thick film is highly active towards oxidizing gases at 200 °C, whereas almost negligible response was observed for reducing gases at all temperatures ranging from RT to 300 °C. The Oxygen adsorption - desorption mechanism is proposed for sensing of NO2 and Cl2 gases, and stated to be favored by n to p type conductivity transition on the surface of sensor film at 200 °C.

PZT\u2013NZF/CF ferrite flexible thick films: Structural, dielectric, ferroelectric, and magnetic characterization

The preparation and properties of thick flexible three-phase composite films based on lead zirconium titanate (PZT) and various ferrites (nickel zinc ferrite (NZF) and cobalt ferrite (CF)) were reported in this study. Properties of three-phase composite films were compared with pure polyvinylidene fluoride (PVDF) and PZT–PVDF films. X-ray diffraction data indicated the formation of well crystallized structure of PZT and NZF/CF phases, without the presence of undesirable phases. Scanning electron micrographs showed that the ceramic particles were dispersed homogeneously in the PVDF matrix and atomic force microscopy confirmed that the size of the particles is around 30 nm. Non-saturated hysteresis loops were evident in all samples due to the presence of highly conductive ferrite phases. Under magnetic field of 10 kOe, composite films exhibited a typical ferromagnetic response. Dielectric properties were investigated in the temperature range from −128 to 250 °C and frequency range of 400 Hz–1 MHz. The results showed that the value of dielectric constant of the PVDF/PZT/ferrite composites increased about 25% above the one obtained for pure PVDF.

Tape casting and characterization of yttrium iron garnet ferrite thick film for microwave substrate application

In this study, the tape casting and characterization of a yttrium iron garnet (YIG) ferrite thick film was carried out for microwave substrate applications. A high-performance YIG ferrite thick film was developed using a well-dispersed non-aqueous YIG slurry. The resulting green YIG film exhibited a smooth surface and a uniform particle-packing structure with a green density of 3.12 g/cm3. The YIG substrate sintered at 1480 °C exhibited a dense microstructure and good properties with a bulk density of 5.06 g/cm3, dielectric constant (εr) of 14.2, dielectric loss (tanδe) of 1.8 × 10−4 (10 GHz), saturate magnetization (4πMs) of 168.2 mT, coercive force (Hc) of 0.47 Oe, and ferromagnetic resonance linewidth (ΔH) of 5.2 KA/m. Thus, the YIG casting film developed in this study was found to be suitable for microwave substrate applications.

Nickel zinc ferrite thick film with linseed oil as organic vehicle for microwave device applications

The properties of nickel zinc ferrite (Ni0·5Zn0·5Fe2O4) thick film with Ni0·5Zn0·5Fe2O4 nanopowders as active powders and linseed oil as the organic vehicle is studied and investigated in this work. Ni0.5Zn0.5Fe2O4 thick film paste samples have been prepared with various weight ratios to study the rheology properties of the pastes. Rheology results show that paste with 30% wt. Ni0.5Zn0.5Fe2O4 has suitable rheological shear-thinning behavior, which is required for formulating screen printing pastes. Dielectric and magnetic properties of the thick film show values lower than bulk Ni0·5Zn0·5Fe2O4, which is relatable to the weight ratio of the ferrite in thick film and thickness of approximately 20 μm. With a low firing temperature of 200 °C, a screen printed microstrip patch antenna with a Ni0·5Zn0·5Fe2O4 thick film layer as substrate overlay has an increase in return loss by 64.22% and also increase in bandwidth by 84.61%, which has shown great potential for microwave devices applications.

Sintering, microwave properties, and circulator applications of textured Sc-substituted M-type ferrite thick films

Sc3+ substituted M-type ferrites are effective microwave magnetic materials with a ferromagnetic resonance frequency in the range of 20 GHz–50 GHz. We report on the fabrication of oriented ferrite thick films as microwave components for application in the Ka-band at 30 GHz. Films of BaFe11.5.Sc0.5O19 were prepared by screen-printing on alumina substrates, drying in an external magnetic field, and sintering at 900 °C. Low-temperature sintering is achieved through use of a mixed BBSZ/CuO sintering aid. A strong anisotropy of the sintered ferrite films is revealed by XRD analysis. Microwave properties of the films were determined in a coplanar waveguide setup. The ferromagnetic resonance frequency of the films is at 30 GHz and the textured films possess good nonreciprocal properties which scale with film thickness. The films were tested in a Y-junction circulator, and represent promising materials for self-biased microwave components fabricated in thick film technology.

Nanocrystalline-modified nickel ferrite films: an effective sensor for industrial and environmental gas pollutant detection

The inverse spinel nanocrystalline pure and doped nickel ferrite particles were synthesized by co-precipitation method. The thick films of both pure and doped nickel ferrite nanoparticles were prepared by coating the material on glass substrate via screen printing method. The XRD was used to confirm cubic, crystalline nickel ferrites. The scanning electron microscopy confirms nanosized, cubic nanoparticles of nickel ferrite, and their morphology was investigated. The energy-dispersive spectroscopy was used to comprise elemental composition for pure and doped ferrites. Transmission electron microscopy was attributed for investigation of surface morphology, crystal structure identification of nickel ferrites. The FT-IR was used to find the vibrational frequencies, symmetric, asymmetric stretching and bending modes of metal oxide linkage. The thick films of nickel ferrite were employed for sensing phenomenon of gases such as LPG, NO2, CH3-OH, C2H5-OH, NH3 and petrol vapours. The pure nickel ferrite showed excellent results for ammonia and nitrogen dioxide gases up to 90.42 and 86.42, respectively. Manganese- and cobalt-doped ferrites were excellent for ammonia and petrol vapours. Modified nickel ferrite effect of dopants cobalt and manganese was investigated. Pure and doped ferrites showed excellent response and recovery for ammonia, NO2, petrol vapours and LPG gases.Graphical abstractThe graphical abstract presenting the synthesis process of pure and modified nickel ferrite prepared by co-precipitation method. The prepared material ferrite thick films were exclusively utilized for the detection of some pollutant gases.

A review of spinel-type of ferrite thick film technology: fabrication and application

Ferrites have emerged out as excellent material for a broad spectrum of applications. Thick films of these materials have great demand for energy and advanced electronics. This review highlights a brief overview of the spinel-type of ferrite thick films (S-FTFs) development right from their historical developments, preparation strategies and state of art applications. The fabrication of S-FTFs includes the discussion on screen-printing, doctor blade tape casting, plasma spray, and spin coating. The comparative analysis of the screen printing technique to the other methods is provided to assist the scientific community during the process of choosing the most suitable fabrication technique. The influence of the synthesis parameters such as temperatures (pre-sintering and final sintering), binders (organic and inorganic), sizes (crystallite, grain, and particle), substrate material and the final heat treatment process in S-FTFs, and the preparation of the ferrite powders and their fabrication technique are review and summarized. Moreover, this review provides a brief overview of the S-FTFs applications, which are classified into four broad categories: sensors, microwave, magnetic and advanced applications. This classification provides a deeper insight into the potential of the S-FTF applications. The motivation in materializing the review of S-FTFs technology is to inspire aspiring research candidates and boost their research interest in this particular field.

Effect of firing temperature on surface morphology of nanosized ferrite-based thick film with linseed oil as organic vehicle

This paper presents the results of morphological study on nanosized nickel zinc ferrite (NZF) thick film using linseed oil as organic vehicle and nanosized NZF powder. First, NZF nanopowder is mixed with organic vehicle which consists of linseed oil, m-xylene and α-terpineol. Paste samples were screen printed onto alumina as substrate, dried and fired at different temperatures of 100°C, 200°C, and 300°C, respectively. Microscopic images of the samples and elemental analysis were observed to determine good dispersion of the active powder with the organic vehicle. Based on the results, the nanoparticles were uniformly dispersed, and images of thick films fired at 200°C and 300°C have shown clearly visible particles, indicating that at these temperatures, the organic vehicle has started to evaporate on the surface, revealing nanoparticles of the active powders. The elemental analysis confirmed this idea, of which carbon element of the organic vehicle gradually decreased with increasing temperature.

High-Magnetization Tetragonal Ferrite-Based Films Induced by Carbon and Oxygen Vacancy Pairs.

Herein, a low-temperature thermal decomposition method is utilized to grow new stable tetragonal Fe3O4-based thick ferrite films. The tetragonal Fe3O4-based film possesses high saturation magnetization of ∼800 emu/cm3. Doping with approximately 10% Co results in a high-energy product of ∼10.9 MGOe with perpendicular magnetocrystalline anisotropy, whereas doping with Ni increases electrical resistivity by a factor of 6 and retains excellent soft magnetic properties (high saturation magnetization and low coercivity). A combined experimental and first-principles study reveals that carbon interstitials (CiB) and oxygen vacancies (VO) form CiB-VO pairs which stabilize the tetragonal phase and enhance saturation magnetization. The magnetization enhancement is further attributed to local ferromagnetic coupling between FeA and FeB induced by CiB-VO pairs in a tetragonal spinel ferrite lattice.

Nickel zinc ferrite thick film as substrate overlay for improved performance of microstrip patch antenna

In this paper, nickel zinc ferrite (NZF) nanopowder was mixed with organic vehicle which consists of linseed oil, m-xylene and α-terpineol. Then the mixture was sonicated for 1 hour at 40°C in order to obtain homogenous paste, followed by printing it onto FR4 substrate using the screen printing technique to form the NZF thick film layer before dried at 100°C and later fired at 200°C. A basic square shape patch antenna by using silver paste was printed onto the NZF thick film layer and was compared with another patch antenna which was been printed without the NZF layer. The results showed that the antenna with NZF thick film layer has return loss of -10.97dB, resonant frequency 6.42GHz, bandwidth 3.9 and Q factor of 1.646, which is better compared to the antenna without the layer by 32.81%, 3.22%, 86.60% and 44.69% respectively.

YIG Thick Film as Substrate Overlay for Bandwidth Enhancement of Microstrip Patch Antenna

Research on microstrip patch antenna (MPA) has been growing in the past few decades due to its planar profile and easy fabrication. Its simplicity of structure, which includes a conductive patch, a dielectric substrate, a ground plane, and a microstrip feeder, is making it more popular for integration in devices which are more focused on miniaturization and flexibility. There are, however, a few disadvantages of MPA, such as narrow bandwidth, low power, and limited inexpensive material selection if a current printed circuit board etching fabrication technique is used. Ferrite substrates are known to be able to help overcome this issue, but the properties of bulk ferrites are difficult to control. This paper aims to solve this problem by using thick-film technology, which utilizes a screen printing method to include ferrite thick film in the MPA structure as substrate overlay to help enhance the performance of MPA. Yttrium iron garnet was chosen as the starting ferrite nanopowders, and the preparation and characterization of the ferrite thick-film paste were carried out to investigate properties of the thick film. Results showed that the thick film showed moderate permittivity and permeability, which is suitable for MPA fabrication. The actual fabricated MPA with ferrite thick-film inclusion on FR4 substrate showed that the thick film improved the performance of MPA with low firing temperature of 200 °C. For MPA which is designed to work at 5.8 GHz, the return loss and −3-dB bandwidth improved 100% and 73%, respectively. In conclusion, ferrite thick-film inclusion in MPA fabrication has proven to improve the performance of the antenna in terms of return loss and bandwidth enhancement.

Resonance shifting by ferrite thick film superstrate

Fritless thick films of Ni-Co-Zn ferrites were fabricated by screen printing technique on alumina substrates. Structural analysis was undertaken using X-ray diffraction and Scanning electron microscopy techniques. A new approach for the determination of complex permittivity (?' and ?'' ) using microwave property perturbation is unveiled. Ag thick film microstrip ring resonator (MSRR) with and without the thick film substrate was used for the microwave transmission studies in the frequency region of 8-12 GHz. The microwave conductivity of the thick films lies in the range of 1.779 S/cm to 2.296 S/cm. The penetration depth is also reported within the X-band of microwave frequencies.

An integrated tunable isolator based on NiZn film fabricated by spin-spray plating

An innovative type of tunable isolator with a planar comb-like microstrip transmission line, which generate circular polarization magnetic field, has been realized with polycrystalline NiZn ferrite thick films fabricated by spin-spray plating (SSP) process with thickness of 10μm. The phase compositions, microstructure, magnetic hysteresis loop, and ferromagnetic resonance (FMR) linewidth of NiZn ferrite thick films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and electron spin resonance (ESR) spectrometer, respectively. The NiZn ferrite thick films possess 4800Gauss saturation magnetization and 190Oe FMR linewidth measured at X-band. With an in-plane dc magnetic bias perpendicular to the comb-like microstrip transmission line, the transmission direction of left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) were proved to be opposite. The non-reciprocal ferromagnetic resonance absorption leads to 11.6dB isolation and 5.78dB insertion loss at 17.57GHz with magnetic bias field of 3.5kOe. Furthermore, with external in-plane magnetic fields range from 0.5kOe to 3.5kOe, the central frequency was tuned from 5.63GHz to 17.57GHz. The state-of-the-art tunable isolator with a planar comb-like microstrip transmission line exhibit a great potential to be applied in different microwave components and radar system.

Structural, mechanical and elastic properties of Ni0.7−xCoxZn0.3Fe2O4 nano-ferrite thick films

PurposeThe present communication aims to investigate the influence of cobalt substitution on the structural, mechanical and elastic properties of nickel–zinc ferrite thick films. The changes observed in the crystallite size (D), lattice constant (a), texture coefficient [TC(hkl)] and mechanical and elastic properties of the thick films due to cobalt substitution have been reported systematically.Design/methodology/approachNi–Zn ferrites with the stoichiometric formula Ni0.7−xCoxZn0.3Fe2O4 (where, x = 0, 0.04, 0.08, 0.12, 0.16 and 0.20) were synthesized via solution combustion technique using sucrose as the fuel and poly-vinyl-alcohol as the matrix material. The thick films of the ferrites were fabricated on alumina substrates by the screen printing method. The thickness of the films was 25 μm, as measured by the gravimetric method. The thick films were subjected to X-ray diffraction and Fourier transform infrared spectroscopy.FindingsThe detailed study of variation of lattice parameter (a), sintering density, micro-strain and elastic properties with cobalt (Co+2) substituted was carried out. The remarkable increase in lattice parameter (from 8.369 A° to 8.3825 A°), bulk density and average grain size (69-119 nm) with the cobalt content was due to larger ionic radius of Co2+ compared to Ni2+. Texture analysis [TC(hkl)] reveals all thick films have adequate grain growth in the (311) plane direction. The main absorption bands of spinel ferrite have appeared through infrared absorption spectra recorded in the range of 300-700 cm−1.Originality/valueThe variation in stiffness constants (for isotropic material, C11 = C12), longitudinal elastic wave (Vl), transverse elastic wave (Vt), mean elastic velocity (VMean), rigidity modulus (G), Poisson’s ratio(s) and Young’s modulus (E) with cobalt (Co+2) composition has been interpreted in terms of binding forces found.

Influence of Sn4+ on Structural and DC Electrical Resistivity of Ni-Zn Ferrite Thick Films

Among the soft ferrites, Ni-Zn ferrite is one of the most versatile ceramic materials because of their important electrical and magnetic properties. These properties were improved by substituting Sn4+ in Ni-Zn ferrites with chemical composition of NixZn1+y−xFe2−2ySnyO4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0; y = 0.1, 0.2). To achieve homogenous ferrite powder at lower sintering temperature and smaller duration in nano-size form, the oxalate co-precipitation method was preferred as compared to other physical and chemical methods. Using this powder, ferrite thick films (FTFs) were prepared by the screen printing technique because of its low cost and easy use. To study structural behavior, the FTFs were characterized by different techniques. The x-ray diffraction and thermo-gravimetric and differential thermal analysis studies show the formation of cubic spinel structure and ferrite phase formation, respectively. There is no remarkable trend observed in lattice constants for the Sn4+ (y = 0.1)- and Sn4+ (y = 0.2)-substituted Ni-Zn ferrites. The bond lengths as well as ionic radii on the A-site of Ni-Zn-Sn ferrites were found to decrease with increasing nickel content. The bond length and ionic radii on the B-sites remained almost constant for Sn4+ (y = 0.1, 0.2)-substituted Ni-Zn ferrites. The energy dispersive x-ray analysis confirms the elemental analysis of FTFs. The Fourier transform infrared spectra show two major absorption bands near 400 cm−1 and 600 cm−1 corresponding to octahedral and tetrahedral sites, respectively, which also confirms the formation of the ferrites. The field emission scanning electron microscopy images shows that the particles are highly porous in nature and located in loosely packed agglomerates. The average particle size of the FTFs lies in the range 20–60 nm. Direct current (DC) resistivity of Ni-Zn-Sn FTFs shows the semiconductor nature. The DC resistivity of Ni-Zn-Sn0.2FTFs is lower than Ni-Zn-Sn0.1 FTFs. The DC resistivity is found to decrease with the increase in Ni2+ content up to x = 0.6. It increases thereafter for a further increase in Ni2+ content up to x = 1.0, and a similar trend is observed for the variations of activation energy with Ni2+ content.

Electromagnetic properties of Co substituted Ni–Cd ferrite thick films on inorganic substrate by auto combustion technique

The present paper reports the structural and 8–18 GHz microwave properties of Ni0.4CoxCd0.6−xFe2O4 (x = 0.0, 0.2, 0.4, 0.6) screen printed thick films. The prepared samples were stepwise characterized for TG–DTA, XRD, SEM and for microwave properties. The TG–DTA reveals the phase formation temperature was obtained at 800 °C. The X-ray diffraction pattern shows the nanocrystalline cubic spinel structure whereas SEM shows the grain size of 300 nm with little agglomeration. The microwave transmittance and absorption shows dispersive behavior in both X and Ku bands. The composition x = 0.2 shows much larger and broad band absorbance than that of other composition. The dielectric constant and dielectric loss of ferrite thick films decreases with increase in cobalt content as well as increase in frequency.

Influence of Ni2+ and Sn4+ substitution on gas sensing behaviour of zinc ferrite thick films

Nanocrystalline ferrite powders of NixZn1 − x + yFe2−2ySnyO4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0 and y = 0.1, 0.2) were prepared by oxalate co-precipitation method and characterized by XRD, FT-IR and FE-SEM techniques. The ferrite thick films (FTFs) of all compositions were prepared by screen printing technique and tested for gas sensing behaviour for liquid petroleum gas (LPG), ethanol (C2H5OH) and chlorine (Cl2). For LPG, the sensitivity decreases with an increase in Ni2+ up to x = 0.6. It increases slightly for further increment in Ni2+. For this gas, the sensitivity is higher for higher concentration of Sn4+ (y = 0.2) while the optimum temperatures are smaller than that for lower concentration of Sn4+ (y = 0.1). The response and recovery times increase with the increase in Ni2+ for lower concentration of Sn4+ (y = 0.1), while at higher concentration of Sn4+ (y = 0.2), there is increase (for Ni2+ up to x = 0.6) and decrease (for further increase in Ni2+ up to 1.0) in response and recovery times. For ethanol and Cl2, the sensitivity of Zn FTFs decreases with an increase in Ni2+ and increases with an increase in Sn4+. For these gases, the optimum temperature is found to be higher for higher concentration of Sn4+. The response and recovery times of Zn FTFs for ethanol and Cl2 increase with increasing Ni2+ and Sn4+.