Solid State Synthesis of Double Molybdates of Potassium and Lanthnones and their Conductivity Behaviour
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SOLID STATE SYNTHESIS OF DOUBLE MOLYBDATES OF POTASSIUM AND LANTHNONES AND THEIR CONDUCTIVITY BEHAVIOUR §UBA, K., UDUPA, M.R., AND SYAMASUNDARA RAO, Y. Suba, K. and Udupa, M.R., Department of Chemistry, Technology, Madras 600 036, India. **Syamasundara Rao, Y., Technology, Madras 600 036,
Department India.
of
Indian Institute of
Physics,
Indian
Institute
of
ABSTRACT
Double molybdates, KLn(MoO4 ) 2 and K5 Ln(MoO 4 )4 have been synthesised utilising the solid state reactions of KIO Ln203 and WO3 (Ln=La,Gd,Dy) in appropriate mole ratios, employing thermal analysis techniques. The solid phases have been characterised by IR, XRD studies and magnetic measurements. The d.c. electrical conductivity values of the two molybdates measured in the temperature range 373-623K are found to increase with rise
in temperature.
jump activation the
This observation together with the calculated
enthalpies and the supposed 'layered'
loosely held K+ ion between
type structure with
the layers support the ionic conductivity
mechanism in these samples. INT1WDLKTION Binary molybdates of alkali elements and rare earths are finding use industries as crystalline matrices of optical quantum generators, luminescent coatings and as laser matrices [1,21. The wide variety of in
optical,
magnetic
and other
physico
chemical
properties
shown by
these
double molybdates provide the possibility of selection of methods for the preparation of active solids with desirable properties [3]. In the present study,
we
have
explored
molybdates of K and Ln KIO3' Ln203 and MO3-
the
possibility
of
synthesising
the
double
(Ln=La,Gd,Dy) through the solid state reactions of Thermal analysis techniques havebeen employed to
elucidate the conditions for preparation and to characterise these prepared phases, we made use of infrared, X-ray diffraction and magnetic measurements. There has been considerable interest in the class of compounds with rigid network structures in which the alkali metal ions occupy tunnels or voids with [4].
the aim of observing
Thus,
dimensional conducting the trend,
many
compounds
(8-alumina)
fast alkali-ion transport
with
one
dimensional
and three dimensional
in the
lattice
(8-eucryptite),
two
(Na 3 Zr 2 Si 2 PO1 2 ) transport of
ions have been reported in literature [5-7]. Consistent with a modest attempt has been made to find out the d.c electrical Mat. Res. Soc. Symp. Proc. Vol. 210. @1991 Materials Research Society
412
conductivity of these double molybdates 'layer' type structure with the alkali positions. initial
which are
known
metal
occupying
Though the study is not exhaustive,
measurements
ion
[8,9]
to have interlayer
we present here some of our
and the conclusions based thereon.
Nevertheless,
a
systematic study would unravel more information on these materials. EXPERIMENTAL AnalaR grade samples of KIO 3 and Ln 203 of 99.99% purity (Ln = La, Gd and Dy) have been obtained and used as such. MoO3 is obtained by heating reagent
grade H2MOO. H20 at 400 0C till
complete deh
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