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|Title:||Structure-property studies in (0.8-x)MoO<sub>3</sub>-0.2B<sub>2</sub>O<sub>3</sub>-xK<sub>2</sub>O (0 ≤ <i>x</i> ≤ 0.25) glasses by spectral and magnetic measurements|
|Authors:||Das, B B|
|Keywords:||Structure activity relationships|
|Abstract:||Glasses of the (0.8-x)MoO<sub>3</sub>-0.2B<sub>2</sub>O<sub>3</sub>-xK<sub>2</sub>O (0 ≤ <i style="">x</i> ≤ 0.25) system (S1-S6: <i>x</i> = 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 [OMoO<sub>5/2</sub>]<sup>-</sup>, tetrahedral [BO<sub>4/2</sub>]<sup>- </sup>and trigonal [BO<sub>3/2</sub>] and <i style="">n</i> free oxygen containing trigonal [BO<sub>n+(3-n)/2 </sub>]<sup>n-</sup>(<i>n</i> = 1,2,3) units. The calculated values of the magnetic susceptibilities (~10<sup>-5</sup> 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 (~10<sup>11</sup>-10<sup>12</sup> Hz). The observed electron paramagnetic resonance results show that the lineshapes vary from axially symmetric in binary S1(<i>x</i> = 0) to isotropic in ternary compositions S2(<i style="">x</i>=0.05)-S6(<i>x</i> = 0.25) at 300 and 77 K. Negative <i style="">g</i>-shift indicates that the paramagnetic site Mo<sup>5+</sup>(4<i style="">d</i><sup>1</sup>) exists as molybdenyl, MoO<sup>3+</sup>, 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 <i style="">g</i>- and <i style="">A</i>-interaction matrices between S1(<i>x</i> = 0) and S2(<i>x</i> = 0.05)-S6(<i>x</i> = 0.25) shows<sub> </sub>distinct difference in the network structures of the binary and ternary compositions.|
|Appears in Collections:||IJC-A Vol.49A(04) [April 2010]|
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