• K Singh

Articles written in Bulletin of Materials Science

• Influence of eutectic addition on the electrical conductivity of Li2O:B2O3 system

Addition of three eutectics, Li2SO4:Li2CO3, 3Li2O·Nb2O5:LiNbO3 and AgI:Ag2SO4 has been tried in the Li2O:B2O3 glass system. The electrical conductivity increases with the addition of eutectic. The amount of lithium fraction and the melting point of the eutectic govern the conductivity.

• Aliovalent substitution inβ-Li2SO4 towards conductivity enhancement

Aliovalent sulphates were selected for substitution in β-Li2SO4 at 6% vacancy concentration. The results show that if the guest ions are substituted on the basis of the criteria given for the formation of a solid solution, then it is possible to achieve a considerable enhancement in conductivity especially in the case of isostructural materials.

• Li2SO4: LiNbO3 binary system for solid state battery applications

Different compositions in the Li2SO4-LiNbO3 system have been prepared by adopting the twin roller quenching technique. The electrical conductivity has been measured and the sample with 20 mole% LiNbO3 exhibited maximum conductivity at 573 K. The results have been explained on the basis of XRD, SEM data and vacancy concentration. A number of solid state electrochemical cells were fabricated by varying the electrolyte composition, using Li-metal and MnO2 as anode and cathode respectively. The 80 Li2SO4:20 LiNbO3 composition gave the best cell performance.

• Dielectrics of lead zirconate bonded with barium borate glass

Dielectric constant variation with temperature and frequency is reported for barium-borate glass-bonded lead zirconate. Lowering of the relative permittivity of the ceramic is attributed to the presence of the glass.

• Influence of Ag2SO4 addition on the electrical conductivity of the Li2O:B2O3 system

Glasses in the Li2O:B2O3:Ag2SO4 system were prepared with varying silver sulphate contents. From the present results it can be said that the amorphous matrix accepts Ag2SO4 up to 5 mol% without any devitrification. The enhancement in conductivity with change in the structure of metaborate glass is due to Ag2SO4.

• Lithium borosulphate glasses: an analysis of glass transition temperature results

Lithium borosulphate glasses have been prepared in three different series: (a) (42·5 −x)Li2O:57·5 B2O3:xLi2SO4; (b) 42·5Li2O: (57·5 −x)B2O3:xLi2SO4 and (c) 42·5Li2O:57·5B2O3:xLi2SO4. The glass transition temperature (Tg) of these glasses has been analysed on the basis of the fraction of four coordinated boron which governs the glass structure. The analysis reveals that the addition of Li2SO4 in series (a) and (b) gives rise to increased value of N4 whereas, in series (c) it increases the number of non-bridging oxygens.

• An analysis of the electrical conductivity of the Ag2SO4-K2SO4 binary system

Electrical conductivity of the Ag2SO4-K2SO4 binary system shows three maxima at 20, 70 and 90 mole% of K2SO4 added to Ag2SO4. The first and the third maxima have been explained in the light of intragrain percolation due to lattice distortion, whereas, the second maximum by the surface percolation. The limit of solid solubility has been set at 20 mole% on the basis of evidences obtained from XRD, DTA and SEM techniques.

• An analysis of the electrical conductivity in BaSO4-added Ag2SO4 solid electrolyte system

The compositions (1 −x)Ag2SO4−(x)BaSO4, wherex=0·01 to 0·6, were prepared by slow cooling of the melt. The extent of the solid solubility of Ba2+ in Ag2SO4 was determined by X-ray powder diffraction and scanning electron microscopy. The bulk conductivity of each sample was obtained using a detailed impedance analysis. The partial substitution of Ba2+ results in the enhancement of conductivity in compliance with the classical aliovalent doping theory. A simplistic model based on lattice distortion (expansion) due to partial substitution of Ag+ by the bigger Ba2+ has been considered to explain enhanced conductivity. Beyond solid-solubility limit (5·27 mole%) the BaSO4-dispersed Ag2SO4 conductivity follows the usual trend seen in binary systems. An increase in conductivity in this case is discussed in the light of interfacial reactions and surface defect chemistry. The maximum conductivity in 20 mole% BaSO4 dispersed Ag2SO4 is due to percolation threshold.

• SOx solid state gas sensors: A review

The performance of any solid state electrochemical gas sensor is always rated on its response time, thermodynamic stability, operating temperature, gas sensing ability, sensitivity and gas concentration range which is sensed. Here, we have reviewed the factors contributing towards a gradual development of electrochemical solid state SOx sensor in terms of a continuous tailoring of its two basic components, i.e. solid electrolyte and reference electrode with high ionic and mixed (ionic + electronic) conductivities, respectively.

• Metal mesh-based transparent electrodes as high-performance EMI shields

Electromagnetic interference (EMI) shields in the form of coatings and films are useful for blocking radiations in various household and industrial settings. Being transparent and flexible would enhance their utility domain. In this study, we have fabricated transparent and flexible EMI shields made of metal meshes produced using the crack templating method pioneered in the laboratory. A Cu metal mesh with polyethylene terephthalate (PET) sheet as its substrate exhibited a visible transmittance of $\sim$85% and a sheet resistance of $\sim$0.83 $\Omega$ per square. The shielding efficiency was tested over a wide spectral range of the K$_{\rm u}$ band (12–18 GHz), relevant to communication electronics. The Cu mesh/PET film showed a remarkably high value for total EMI shielding (SE$_{\rm T}$) with the average value being $\sim$41 dB. The film could be laminated using a commonly available method, thus protecting exposure of the mesh to the environment. The laminated film is multifunctional, and this aspect was demonstrated by fabricating a large area (3.5 $\times$ 2.2 cm$^ 2$) Joule heater for defrosting and defogging applications.

• # Bulletin of Materials Science

Volume 44, 2021
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020