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Indian Journal of Chemistry -Section A (IJC-A) >
IJC-A Vol.49A [2010] >
IJC-A Vol.49A(04) [April 2010] >
| Title: | Structure-property studies in (0.8-x)MoO3-0.2B2O3-xK2O (0 ≤ x ≤ 0.25) glasses by spectral and magnetic measurements |
| Authors: | Das, B B
Ambika, R |
| Keywords: | Structure activity relationships
Glasses
Magnetic properties
EPR spectroscopy
IR spectroscopy |
| Issue Date: | Apr-2010 |
| Publisher: | CSIR |
| Abstract: | Glasses of the (0.8-x)MoO3-0.2B2O3-xK2O
(0 ≤ x
≤ 0.25) system (S1-S6: x = 0,
0.05, 0.10, 0.15, 0.20, 0.25) have been prepared by air quenching the melt in
the range 1073-1173 K. Glassy phase has been ascertained by powder X-ray diffraction patterns of
the samples. Differential thermal analysis results show the glass transition
temperature in the range 573-673 K. Infrared spectral results at 300 K show the
presence of octahedral [OMoO5/2]-, tetrahedral [BO4/2]-
and trigonal [BO3/2] and n
free oxygen containing trigonal [BOn+(3-n)/2 ]n-(n
= 1,2,3) units. The calculated values of the magnetic susceptibilities (~10-5
emu/gG) from magnetic moment data at 300 K show the weak paramagnetic nature of
the glasses.
The magnitude of the calculated exchange integrals of the small polaron is
found to be in the range 0.003-0.058 eV
(~1011-1012 Hz). The observed electron paramagnetic
resonance results show that the lineshapes vary from axially symmetric in
binary S1(x = 0) to isotropic in ternary compositions S2(x=0.05)-S6(x = 0.25) at 300 and
77 K. Negative
g-shift indicates that the
paramagnetic site Mo5+(4d1)
exists as molybdenyl, MoO3+, ion in the glasses. The partially
resolved hyperfine structures indicate that the small polaron hopping depends
on temperature as well as on the glass network. Appreciable difference in the
values of g- and A-interaction matrices between S1(x = 0) and S2(x =
0.05)-S6(x = 0.25) shows distinct difference in the network
structures of the binary and ternary compositions. |
| Page(s): | 425-430 |
| Source: | IJC-A Vol.49A(04) [April 2010]
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