Munia Ganguli

Fast solid state synthesis of metal vanadates and chalcogenides using microwave irradiation

Metal vanadates and chalcogenides have been prepared in rapid time scales using a domestic microwave oven. The products exhibit high phase purity and homogeneity. The thermal and spectroscopic properties of the microwave prepared metal vanadates match well with those prepared by conventional methods.

Synthesis of β-SiC powder by use of microwave radiation

Monophasic β-SiC powder has been synthesized in a commercial microwave oven operating at 2450 MHz and power levels up to 980 W. This simple method of solid-state synthesis involves a direct reaction between silicon and charcoal powder at temperatures lower than 1250 K.

Lithium ion transport in Li2SO4–Li2O–P2O5 glasses

Abstract Electrical conductivity and dielectric relaxation studies on a large number of lithium ion conducting glasses belonging to the ternary glass system Li 2 SO 4 –Li 2 O–P 2 O 5 have been carried out over a wide range of temperature (150 K to 450 K) and frequencies (10 Hz–10 7 Hz). DC conductivities exhibit two different activation regions. This seems to be suggestive of the presence of a cluster-tissue texture in these glasses. The clusters may be of both Li 2 SO 4 and lithium phosphate and are held together by a connective tissue of average composition. This conjecture seems to be well-supported by the ac conductivity behaviour of these glasses which have been analysed using both power law and stretched exponential relaxation functions.

Studies of ternary Li2SO4–Li2O–P2O5 glasses

Glasses in a wide range of compositions in the ternary system xLi(2)SO(4-y)Li(2)O-zP(2)O(5) where x ranges from 0 to 30 mol%, y ranges from 35 to 55 mol% and z ranges from 25 to 50 mol% have been prepared and their properties measured using infra-red, Raman, and P-31 magic angle spinning nuclear magnetic resonance spectroscopic techniques. We conclude that a random close packing of phosphate and sulphate ions which also leads to formation of connected voids in the structure is consistent with our data. There is also evidence for formation of condensed sulphate-phosphate species in the liquid which may be retained in the glass structure

Li+ ion conductivities in boro-tellurite glasses

Lithium ion conductivity has been investigated in a boro-tellurite glass system, LiCl.LiBO2.TeO2. In the absence of LiCl, the conductivity increases with increasing non-bridging oxygen (NBO) concentration. LiCl addition has little influence on total conductivity although the observed barriers are low. Formation of LiCl clusters appears evident. In the a.c. conductivity and dielectric studies, it is observed that the conductivity mechanism remains the same in all compositions and at all temperatures. A suggestion is made that Li+ ion transport may be driven by bridging oxygen ↔r non-bridging oxygen (BO ↔r NBO) switching, which is why the two different types of Li+ ions in the clusters and in the neighbourhood of NBOs, do not manifest in the conductivity studies.

ROLE OF PbO IN LITHIUM ION TRANSPORT IN Li2O-PbO-B2O3 GLASSES

Abstract: A wide range of compositions of grasses in the ternary Li2O-PbO-B2O3 glass system was prepared, and de and ac conductivity measurements were carried out on these glasses. The presence of lead leads to a decrease in de conductivities and an increase in the activation energies. This is likely to be due to the increase of the partial charges on the oxygen atoms and to the presence of the lone pair on the Pb atom; both of these factors impede lithium ion motion. The ac conductivity and dielectric behavior of these glasses support such a conjecture

Conductivity studies in SnO-NaPO3 glasses

Na+ ion conductivity has been studied in SnO·NaPO3 glasses, which have been prepared over a wide range of compositions using a microwave melting technique. D.c. activation barriers seem to reflect the structural changes in system. A.c. conductivity analysis has revealed that while the power law exponent, s, seem to bear correlation to the structural changes, the exponent β of the stretched exponential function describing the dielectric relaxation is largely insensitive to the structure. Possible importance of the correlation of transport property to the variation of available non-bridging oxygen (NBO) atoms in the structure is discussed.