Ionic conductivity in Na2(R,Me)3+M4+P3O12 crystals

Ionic conductivity in Na2(R,Me)3+M4+P3O12 crystals

135 Positron-electron R. K. BATRA”, penetration in rare earths* P. S. TAKHER” and M. L. SEHGALb a Physics Department, Punjab Agricultural Univers...

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135

Positron-electron R. K. BATRA”,

penetration in rare earths*

P. S. TAKHER”

and M. L. SEHGALb

a Physics Department, Punjab Agricultural University, Ludhiana (India) h Physics Department, Aligarh Muslim University, Aligarh (India) The present investigation show that projected range R, * and R,- decrease with the atomic number Zfor the rare earth elements, also, for a given rare earth element, R,’ is larger than R,- at all energies. Further, a decrease in csda range at different energies in ytterbium and yttrium because of multiple scattering effects has been found. The difference between rare-earth ranges has a maximum around 0.8 MeV and decreases till 2.0 MeV, whereafter it becomes practically constant. The measured ratio of positron range at 1.88 MeV to electron range at 1.77 MeV in yttrium and ytterbium agree with the present theory. However, there is a large discrepancy between theory and experiment in holmium and neodymium. Hence there is a need for further measurements of the rare earth ranges.

Ionic conductivity K. BYRAPPA”,

in Na,(R,Me)3+M4+P30,,

A. B. KULKARNP

crystals*

and G. S. GOPALAKRISHNA”

a Department of Geology and The Mineralogical Institute, University of Mysore, Manasa Gangotri, Mysore, 570006(Zndia) b Department of Physics, University of Gulbarga, Gulbarga, Karnataka, 585106(India) With a slow decline in the popularity of NASICON in high temperature, battery devices, materials scientists are now searching for simple sodium superionic conductors. Na,(R,Co)ZrP,O, z (where R = La, Ce, Pr, Nd) and Na,(La,Me)ZrP,O,, (where Mr = Co, Al, Cr) have been earlier reported as prospective sodium superionic conductors that yield very interesting results. Naz(R,Me)3+MJ+P,0,z (where R = La, Ce, Nd; Me3’ = Co, Al, Cr; M4* = Ti, Zr) crystals have been synthesized by the hydrothermal technique. The crystals are well-developed with different colours and vitreous lustre having a size of l-3 mm. The impedance measurements have been carried out for all the representative samples using silver blocking electrodes within a wide range of temperature (25300 ‘C) and a.c. internal frequency (100 Hz-10 kHz). The corresponding Arrhenius and admittance plots are given for the representative samples, and the values of activation energy for them have been calculated. The ionic conductivity in compounds containing zirconium is higher than in compounds containing titanium among M4’ elements. Similarly, the ionic conductivity in these compounds varies with the concentration of sodium, R, Me3+ and M4elements.

Study of hydrogenation KAVITA

S. JERATH.

on Gd,,Ga,,Ni,,

H. S. CHAUHAN

by the XANES

method*

and K. B. GARG

Department of Physics, University of Rajasthan, Jaipur (Rajasthan), Jaipur 302004 (India)

H:R

The experimental study shows that almost all of the elemental rare earths absorb hydrogen to ratios of 3 and there exist many crystalline rare-earth transition-metal intermetallic

*Abstract of a paper presented at the 17th Rare Earth Research University. Hamilton, Ontario, Canada, June 9-12. 1986. 0022.5088/86/$3.50

Conference,

I’ Elsevier Sequoia/Printed

McMaster

in The Netherlands