On the Infra Red Spectra of Semiconducting Ferrites

ARTICLE 32: trusciencetrutechnology@blogspot.com
Volume 2009-2010 Issue No.6, Dt. 15th June.2010 the 70th B’Day Volume of Professor Kotcherlakota Lakshmi Narayana

On the Infra Red Spectra characterization of Semiconducting Ferrites Ni_xZn_1-xFe₂O₄ and their hysteresis.
By
Prof.Dr. Kotcherlakota Lakshmi Narayana
&
Miss. Mali Hemlata Raghunath,
General Physics Laboratory,
Dept. of Phys., Shivaji University, Kolhapur (during 1997-1998)

The Infra Red Spectra were recorded on IR-spectrometer. The pellets used for recording spectra were prepared with mixing KBr in a small amount of ferrite powder. The range of frequencies selected is 200 to 800 cm ^-1. This facility is made available by USIC originally conceived and promoted extensively by Prof. Dr. K. L. Narayana who insisted on creation of USIC facilities at Shiva University, Kolhapur since his first four PhD research guidance to Dr B. P. Sabale, Dr. M.K.Soudagar, Dr.C.I.Patil and Dr. N.S. Dhaygude. He also helped P. Parmeswaran Pillai under (Krishna Pillai, HOD, at SU Kolhapur who is a student from Anna University, under K.Venketeswarulu and IVVRaghavacharyulu, later a friend of KLN also who was at Uppsala University, Sweden), to complete his PhD research work on Force Constants.

The IR spectra images are given. There are four active modes which triply degenerate for normal spinel. For inverse and partly inverse spinels triply degenerate vibrations may split into four vibrations. If the splitting is not too large and there is certain statistical distribution of various cations over tetrahedron and octahedron, one cannot observe the splitting but only the broadening of the absorption band. In the present series Ni ferrite is inverse ferrite. The intensity of octahedral decreases and broadens around 410cm ^-1 for the second series. For the third series the intensity of octahedral no much decrease but found broadened.

ν ₁ corresponds to stretching of tetrahedral metal ν ₂ corresponds to the vibration of metal ions in the isotropic force fields of their octahedral environment. The ordering of cations, result in lowering of the overall symmetry which, in turn leads to an increase in number of IR active vibrations. So IR spectrum of the ordered spinel will show a fine structure. Ionic ordering in some cases may not be detectable with x-ray diffraction. But this can be detected by IR spectroscopy. This ionic ordering may cause the distortion of the electronic nature.

RESULTS:

IR absorption data for samples sintered at 1100 deg C for 30 hours.

Below listed are the observation number with the chemical formula

of the sample followed by listings for each case of tetrahedrala and octahedral

the two different vibrational frequencies assigned.

Obs. Number Chemical Formula 

Tetrahedral1 cm-1 Tetrahedral 2 in cm-1  Octahedral 1 cm-1 Octahedral 2 in cm-1

1 Ni_.4Zn_.6Fe₂O₄
570 560 440 400

2 Ni_.25Zn_.75Fe₂O₄
570 545 410 410

3 Ni_.3Zn_.7Fe₂O₄
560 545 420 410

There are two peaks found at the tetrahedral and octahedral band positions. Our finding is that minor modifications in the values of g, ν ₁ corresponds to stretching of tetrahedral metal ν ₂ occurs in the spinels that we have developed at our laboratories. The present spectra show the fine structure and the intensity of fine structure increases with Fe (iron) content. Therefore the observed structure may be due to iron ion ordering. Also IR spectrum did not change which inference that large number of IR active modes is not caused by the ordering in the presence of two kinds of cations on just the one sub-lattice. The frequency of vibration is determined by various parameters like cationic masses the bonding forces and the cation-anion distances.

Acknowledgment:

I have been introduced to Prof Herzberg and his wife at the Indian Science Congress Session held in Andhra University, when the second time The Canadian Professor and Nobel Laureate paid a visit to the Prof. K. Rangadhama Rao’s laboratories of Science & Technology at AU, Waltair Due to the demise of Prof K. R. Rao D.Sc.(Madras)D.Sc.(London), his ardent students like Professor PTRao, Prof. C. Santhamma of AU, Dr. K. Appala Narasimham from BARC, Dr. C. Ramashastri from IIT, Madras and Prof Dr K. S. Rao of Karnataka University, Dharwad have graced the occasion.