Far infrared reflectance of sintered nickel manganite samples for negative temperature coefficient thermistors

Single phase complex spinel (Mn, Ni, Co, Fe){sub 3}O{sub 4} samples were sintered at 1050, 1200 and 1300 deg. C for 30 min and at 1200 deg. C for 120 min. Morphological changes of the obtained samples with the sintering temperature and time were analyzed by X-ray diffraction and scanning electron microscope (SEM). Room temperature far infrared reflectivity spectra for all samples were measured in the frequency range between 50 and 1200 cm{sup -1}. The obtained spectra for all samples showed the presence of the same oscillators, but their intensities increased with the sintering temperature and time in correlation with the increase in sample density and microstructure changes during sintering. The measured spectra were numerically analyzed using the Kramers-Kroenig method and the four-parameter model of coupled oscillators. Optical modes were calculated for six observed ionic oscillators belonging to the spinel structure of (Mn, Ni, Co, Fe){sub 3}O{sub 4} of which four were strong and two were weak.

[1]  Rainer Schmidt,et al.  Small polaron hopping in spinel manganates , 2005 .

[2]  D. Roessler,et al.  Kramers-Kronig analysis of reflection data , 1965 .

[3]  H. Lutz,et al.  Lattice vibration spectra. LIX. Single crystal infrared and Raman studies of spinel type oxides , 1991 .

[4]  C. Leroux,et al.  Cation Distribution, Short-Range Order and Small Polaron Hopping Conduction in Nickel Manganites, from a Neutron Diffraction Study , 1999 .

[5]  E. Talik,et al.  Physical properties and X-ray diffraction of a NiMn2O4 single crystal below and above the ferrimagnetic transition at Tc = 145 K , 1997 .

[6]  A. Rousset,et al.  Mechanical properties of nickel manganites-based ceramics used as negative temperature coefficient thermistors (NTC) , 2004 .

[7]  K. Park,et al.  Electrical properties of Ni–Mn–Co–(Fe) oxide thick-film NTC thermistors prepared by screen printing , 2003 .

[8]  François Gervais,et al.  Temperature dependence of transverse- and longitudinal-optic modes in TiO 2 (rutile) , 1974 .

[9]  S. A. Obrad,et al.  Volume air flow sensors based on NTC thick film segmented thermistors , 2006 .

[10]  M. V. Nikolić,et al.  Thermal diffusivity and electron transport properties of NTC samples obtained by the photoacoustic method , 2006 .

[11]  V. Srinivasan,et al.  Distribution of Metal Ions in Transition Metal Manganites AMn2O4 (A: Co, Ni, Cu, or Zn) , 1982, January 16.

[12]  D. Rousseau,et al.  Normal mode determination in crystals , 1981 .

[13]  O. Aleksic,et al.  Segmented Thermistors Printed by NTC Nanometric Paste and Applied in Volume Air-Flow Sensors , 2006 .

[14]  R. Gover,et al.  Study of the preparation conditions for NiMn2O4 grown from hydroxide precursors , 2006 .

[15]  F. Gervais,et al.  Ab initio investigation of phonon modes in the MgAl2O4 spinel , 2002 .

[16]  Rainer Schmidt,et al.  Production of NTCR thermistor devices based on NiMn2O4+δ , 2004 .

[17]  K. Paraskevopoulos,et al.  Far infrared properties of sintered NiO , 2007 .

[18]  K. Paraskevopoulos,et al.  Infrared properties of sintered α-MnSe , 2006 .

[19]  M. Lenglet,et al.  CORRELATION BETWEEN IONIC-COVALENT PARAMETERS AND INFRARED SPECTROSCOPIC DATA IN II-III TRANSITION METAL SPINEL-TYPE OXIDES , 1997 .

[20]  I. Reaney,et al.  Correlation between microstructure and conductance in NTC thermistors produced from oxide powders , 1999 .

[21]  Valery V. Skorokhod,et al.  Advanced Science and Technology of Sintering , 1999 .

[22]  Abel Rousset,et al.  Correlation between the structure, the microstructure and the electrical properties of nickel manganite negative temperature coefficient (NTC) thermistors , 1998 .