Dr. Shridhar N Mathad | K.L.E.I.T. hubli (original) (raw)

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Papers by Dr. Shridhar N Mathad

We report structural and microwave properties of rod shaped bismuth strontium manganite , thick-f... more We report structural and microwave properties of rod shaped bismuth strontium manganite , thick-films prepared by screen printing method. The orthorhombic phase formation was confirmed by XRD. The micro rods like morphology and grain size were observed by using SEM analysis. Modification in microstripline properties like microwave absorption , transmittance, and effective dielectric constant which is being done by simple superstrate Bi 1−x Sr x MnO 3 (BSM) thick-films at very high frequencies (microwaves). The effective dielectric constant is due to superstrate, which lies in between 10.41 to 29.22 for thick films.

Nanocrystalline nickel ferrite was synthesized by a low cost and simple co-precipitation method. ... more Nanocrystalline nickel ferrite was synthesized by a low cost and simple co-precipitation method. The structural and mechanical properties were studied. The result showed the single phase formation of the cubic nickel ferrite, which was confirmed by thermo-gravimetric analysis (TG/DTA) and X-ray diffraction data. The grain size and the surface morphology were studied by scanning electron microscopy (SEM). The structural parameters, force constant (K), stiffness constant (C 11 ), elastic wave velocity (V m ), bulk modulus (B), Young's modulus (E), rigidity modulus (G), Poisson's ratio (P), and Debye temperature (O D ) were obtained from Fourier transform infrared spectroscopy (FT-IR) data, which are reported.

This paper analyzes the properties of environment friendly lead free ferroelectrics at microwave ... more This paper analyzes the properties of environment friendly lead free ferroelectrics at microwave (MW) frequencies.

Bismuth strontium manganites Bi 1 -x Sr x MnO 3 (0.20 ≤ x ≤ 0.50) belonging to the orthorhombic s... more Bismuth strontium manganites Bi 1 -x Sr x MnO 3 (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) Sr x MnO 3 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 (ρ D ), 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 BiMnO 3 thick films.

Index Terms-effective dielectric constant, microstripline, superstrate method.

NiFe 2 O 4 nanopowder was synthesized by co precipitation method. Precursors were mixed in a desi... more NiFe 2 O 4 nanopowder was synthesized by co precipitation method. Precursors were mixed in a desired stoichiometric ratio and calcined at about 800°C to get nickel ferrite nanopowder. The synthesized nickel ferrite was characterized by XRD. The structural parameters such as the lattice constant (a), volume, average crystallite size (D), texture coefficient (TC) and lattice strain (η) have been determined.

The properties of nanocrystalline lead zirconate titanate [PZT, Pb(Zr 0.52 Ti 0.48 )O 3 ] thick f... more The properties of nanocrystalline lead zirconate titanate [PZT, Pb(Zr 0.52 Ti 0.48 )O 3 ] 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 agglomera tion, 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 syn thesized materials. The real part of permittivity and dielectric loss were found to decrease with increasing fre quency.

This paper reports, the structural, dielectric and transport properties of Sr x Ba 1− x Nb 2 O 6 ... more This paper reports, the structural, dielectric and transport properties of Sr x Ba 1− x Nb 2 O 6 [SBN] for x =0.4 and 0.5, prepared by traditional sintering method (solid state reaction technique). The tetragonal tungsten bronze type crystal structure, structural parameters such as the lattice constant (a =12.63946Å, b = 12.63946Å, c =3.978203462Å), average crystallite size (61.62 nm-95.17nm ), and texture coefficient (TC) have been determined using X-ray diffraction data. TGA-DTA analysis reveals that formation of oxide phase takes place beyond 1050 • C. Rod shaped surface morphology has been obtained. The fundamental vibrational mode observed in finger print region by FTIR reveals formation of SBN ceramics. The variation of real of part dielectric constant (έ) and loss tangent (tanδ) was studied at room temperature. The dispersion of dielectric constant with frequency indicates relaxor nature of SBN.

Purpose -The purpose of this paper was to determine the complex permittivity of bismuth strontium... more Purpose -The purpose of this paper was to determine the complex permittivity of bismuth strontium manganites (Bi 12 x Sr x MnO 3 ) 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 Bi 12 x Sr x MnO 3 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 increase in Sr content in bismuth manganite and it is higher for bulk as compared to its thick films. The superstrate on Ag thick film microstrip ring resonator is an efficient tool capable of detecting the composition dependent changes in microwave properties of ceramic bulk and thick films.

Strontium barium niobates (Sr x Ba 1−x Nb 2 O 6 have been synthesized by solid state sintering te... more Strontium barium niobates (Sr x Ba 1−x Nb 2 O 6 have been synthesized by solid state sintering technique. The structural aspects were studied by X-ray diffraction, FTIR, Raman spectroscopy. The grains of crystallites having diverse shapes have been observed. The microwave properties like microwave absorption, dielectric constant and conductivity of strontium barium niobate ceramics (0.04 ≤ x ≥ 0.75) has been investigated from 8 GHz to 18 GHz frequencies. The permittivity shows a large variation with strontium content and found maximum for x = 0.50. The dielectric constant lies in the range 3.9 to 23.8. Microwave conductivity decreases with increase in strontium content and in the range 0.17 to 6.5 S/cm. The microwave conductivity measurement reveals the loss of polaron conduction which supports the dielectric loss in the microwave region where minima at 10.8 and 16 GHz has been obtained.

This paper reports a study on the microstructure, electrical and microwave properties of fritless... more This paper reports a study on the microstructure, electrical and microwave properties of fritless thick films of Ni 0.6 Cu 0.4 Fe y Mn 2−y O 4 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.

The influence of the Fe on the microstructure, electrical and dielectric properties of Ni 0.6 Cu ... more The influence of the Fe on the microstructure, electrical and dielectric properties of Ni 0.6 Cu 0.4 Fe y Mn 2Ày O 4 (0.1 y 0.5) negative temperature coefficient (NTC) thermistors prepared by well known simple chemical co-precipitation method were studied. The replacement of manganese by iron plays an important role in changing the lattice parameter, X-ray density, sintered density, porosity, DC resistivity at different temperatures and dielectric properties at different frequencies. The X-ray and sintered density increased linearly and porosity decreased with iron. The room temperature resistivity of nickel copper manganite NTC ceramic decreased from 1 MV cm to 68 KV cm and dielectric constant increased from $9 Â 10 7 to 1.5 Â 10 9 at 20 Hz as iron content increased. #

The present investigation was aimed to synthesize bismuth strontium manganite of composition Bi 0... more The present investigation was aimed to synthesize bismuth strontium manganite of composition Bi 0 . 6 Sr 0 . 4 MnO 3 ceramic by low cost solid state technique. The ceramic showed orthorhombic crystal structure with micro-rod like surface morphology. The crystallite size was 34nm, with preferential orientation in plane with TC of 2.15. On the basis of Zener polaron model and conventional model, possible Raman vibrational modes in bismuth strontium manganites have been assigned.

Rods of Bi 1−x Sr x MnO 3 (BSM) (0.20 ≤ x ≤ 0.50) having different dimensions were synthesized by... more Rods of Bi 1−x Sr x MnO 3 (BSM) (0.20 ≤ x ≤ 0.50) having different dimensions were synthesized by the solid state reaction method. The replacement of bismuth by strontium in BSM plays an important role in changing the cell volume, and DC resistivity. The surface morphology varied with strontium content and changes from cubic to rods of different sizes. The room temperature resistivity of BSM decreases with strontium from 0.21 M cm to 0.11 M cm. These manganites follow the Arrhenius equation. The thermistor constant increases with Sr content from ∼ 793 K to 1735 K, the maximum being for x = 0 20 and minimum for x = 0 50.

Bismuth strontium manganites (BSM) with variation in strontium content have been synthesized by s... more 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 (ε') 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.

Index Terms-effective dielectric constant, microstripline, superstrate method.