S. N. Mathad

Structural and mechanical properties of Sr+2-doped bismuth manganite thick films

Bismuth strontium manganites Bi1 − xSrxMnO3 (0.20 ≤ x ≤ 0.50) belonging to the orthorhombic structural family were prepared in furnace using a solid-state reaction technique. Thick films of Bi(1 − x)SrxMnO3 were prepared by simple screen printing route. X-ray diffraction data suggest that the synthesized materials have an orthorhombic structure. For synthesized materials, texture coefficient (TC), dislocation density (ρD), density of crystallites per unit area (ψ), and mechanical properties are reported along with the influence of x on the structure and mechanical properties of BiMnO3 thick films.

Dielectric spectroscopy and microwave conductivity of bismuth strontium manganites at high frequencies

Bismuth strontium manganites (BSM) with variation in strontium content have been synthesized by simple solid state reaction method. X-ray diffraction data show that the samples have orthorhombic structure with crystallite size ∼40 to 60 nm. SEM studies reveal morphology of micro-rods and micro-flakes. The dielectric constant (ɛ′) and the dielectric loss (tan δ) decreases with the strontium content and the applied frequency which has been attributed to Maxwell-Wagner polarization. The microwave conductivity of samples decreases from 8.9 S/cm to 2.29 S/cm at 8.2 GHz as strontium increases. The penetration depth has also been reported at microwave frequencies from 8–18 GHz.

Properties of fritless Ni0.6Cu0.4FeyMn2−yO4 NTC ceramic thick films

This paper reports a study on the microstructure, electrical and microwave properties of fritless thick films of Ni0.6Cu0.4FeyMn2?yO4 negative temperature coefficient (NTC) ceramic. Substitution of Fe has an important effect on the lattice parameter, x-ray density, thermistor constant and microwave properties in the GHz frequency range. The x-ray density increased linearly and the lattice parameter decreased with iron concentration. The Raman intensity mode around 720?cm?1 increased and shifted towards lower frequency with an increase in Fe content. The room temperature electrical resistivity of these thick films decreased from 2.8 to 0.37?M??cm and the microwave permittivity as well as absorption increased as the iron content increased.

Microwave Studies of Environmental Friendly Ferroelectrics

The structural and microwave studies of lead-free barium niobates ceramics prepared by the high temperatures solid state reaction technique are reported. The structural parameters such as the lattice constants, average crystallite size (D), texture coefficients (TC), dislocation density, and microstrain have been determined using X-ray diffraction data. Surface morphological studies were carried out using scanning electron microscopy (SEM) technique. The strong absorption bands at ~816 cm−1, 641 cm−1, and 482 cm−1 are associated with the coupling mode between Nb–O stretching modes observed in FTIR studies. The electromagnetic transmittance, absorption, studies of barium niobates in the X band frequency range frequencies using waveguide reflectometer technique are reported.

Structural and mechanical properties of Sr-doped barium niobate thick films

Polycrystalline strontium barium niobates SrxBa1 − xNb2O6 (SBN, 0.40 ≤ x ≤ 0.75) were prepared by standard solid state ceramic method at relatively at low temperatures. Thick SBN films prepared by simple, low-cost, screen printing route were characterized by XRD. Preliminary structural analysis exhibits the formation of tetragonal tungsten bronze crystal structure at room temperature. Texture coefficient [TC(hkl)], dislocation density (ρD), density of crystallites per unit surface area (Ψ), mechanical properties, and microwave behavior of synthesized materials are reported.

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

Purpose The 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/approach Ni–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. Findings The 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/value The 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.

Microwave studies by perturbation of Ag thick film microstrip ring resonator using superstrate of bismuth strontium manganites

Purpose – The purpose of this paper was to determine the complex permittivity of bismuth strontium manganites (Bi1−xSrxMnO3) in the 8‐12 GHz range by using perturbation of Ag thick film microstrip ring resonator (MSRR) due to superstrate of both bulk and thick film.Design/methodology/approach – The BSM ceramics were synthesized by simple low cost solid state reaction method and their fritless thick films were fabricated by screen printing technique on alumina substrate. A comparison has been made between the X band response of Ag thick film microstrip ring resonator due to perturbation of bulk and thick film Bi1−xSrxMnO3 ceramic.Findings – The bulk and thick film superstrate decreases the resonance frequency of MSRR. In this technique even minor change in the properties of superstrate material changes the MSRR response. Variation of strontium content also influences microwave conductivity and penetration depth of bulk and thick films.Originality/value – The microwave complex permittivity decreases with in...

Combustion synthesis and electromagnetic properties of nanocrystalline Pb(Zr 0.52 Ti 0.48 )O 3

The properties of nanocrystalline lead zirconate titanate [PZT, Pb(Zr0.52Ti0.48)O3] thick films and pellets synthesized by self-propagating auto combustion route using sucrose as a fuel are reported. The X-ray diffraction reveals the formation of nanocrystalline tetragonal PZT having a particle size of 5.52 nm in thick films and 7.08 nm in bulk material. SEM images show the grain size of 300–400 nm with some agglomeration, as well as modified open grain boundaries and grain growth in the PZT thick film as compared to the bulk material. The DC electric resistivity of PZT shows semiconducting behavior. We also characterized the 8–18 GHz microwave insertion loss, absorption, complex permittivity, and microwave conductivity of synthesized materials. The real part of permittivity and dielectric loss were found to decrease with increasing frequency.

Structural and mechanical properties of nanograined magnesium ferrite produced by oxalate coprecipitation method

Magnesium ferrite (MgFe2O4) was prepared by simple low-cost oxalate coprecipitation method and characterized by XRD and SEM. The X-ray analysis confirmed the formation of a single-phase cubic spinel structure. The product revealed a non-uniform morphology and some certain extent of agglomeration. Crystallite size, texture coefficient, dislocation density, hopping length, and mechanical properties of the product are also reported.

Shielding of metals from the corrosion induced by water and humidity by using scratch resistant and hydrophobic silica coatings

Abstract The objective of the present paper is to demonstrate the effect of sol-gel derived scratch resistant coatings on different metal surfaces for anticorrosive applications. However, practical applications are limited by problems intrinsic to sol-gel processing or specific of coating/metal systems. Coatings aimed to improve oxidation and wet corrosion resistance have been studied the most. The results published in the literature show that sol-gel coatings may offer good protection against oxidation. More difficult is to achieve a protection against wet corrosion. An important aspect of the application of the sol-gel method for coating metallic objects is also the deposition technique.