FTIR Study of Diamagnetic Mg²⁺ Substituted Ni₂Z Hexaferrite

FTIR Study of Diamagnetic Mg²⁺ Substituted Ni₂Z Hexaferrite

Suhasini Dafe1*, Maheshkumar Salunkhe2

1*,2Department of physics Institute of Science Nagpur, Maharashtra, India

Abstract FTIR spectrum of Sr3MgxNi2-xFe24O41 Z-type Hexaferrite heated at 1250 °C was recorded in the mid IR range (4000 cm1 to 400 cm1). The spectra obtained specify the band position with respect to substituted cations. The band position at about 441 cm-1 and 609 cm-1 attributed to the vibration of octahedral and tetrahedral cluster respectively. Broad absorption band found in the spectra describe the complex nature of the Z-type hexaferrite. Shoulders observed in the spectra evidenced for presence of Fe2+ in the hexaferrite. Variation in the intensities of absorbed bands attributed to the change in the dipole moment with Mg2+ substitution.

Keywords FTIR, Z-Type, Ceramic, Band Positions, Atomic Weight

1. INTRODUCTION

   Infrared spectroscopy is used to determine local symmetries in crystalline, non crystalline solids and ordering phenomenon in spinel [1]. From the IR spectra the optical, oscillator parameter as well as effective ionic charges was computed by KK, DA, DA-KK methods by E. Z. Katsnelson 1989 [2]. The absorption bands in ferrites mainly arise from lattice vibration of oxide ions with cation producing varies frequencies of the unit cell. The frequencies of vibration depend on various factors such as atomic mass, unit cell parameters, cation oxygen bonding [1]. Thus IR study help to illustrate cationic arrangement, bonding strength as well bonding frequency of vibration of hexaferrite.

   In the present study, the IR spectra of Mg2+ substituted Ni2Z hexaferrite were investigated for first time to study the ordering in Z-type hexaferrite as a function of content of Mg2+ ions and probable evidence of Fe2+ ions.

2. EXPERIMENTAL

   In this paper we present FTIR spectra of Sr3MgxNi2- xFe24O41 (x = 0, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2)

   hexaferrite prepared by solid state reaction at 1250°C for 6 h

   using AR grade oxides and carbonate. These pallets of compositions were first heated at 900°C for about 5 hr and then cooled at room temperature. Then the temperature of furnace was set to 1250°C and kept it constant for 6 hr. The furnace is then cooled slowly at the rate of 20°C per hour up to 1000°C and then allows the furnace cooled in natural way to room temperature. The formation of the Z hexaferrite was confirmed by X-ray diffraction studies carried out on powder samples by using CuK radiation. All the samples showed single phase formation. The FTIR spectra of all prepared

   hexaferrite were obtained by using Bruker, Germany 3000 Hyperion Microscope with Vertex 80 FTIR System in the range 4,000 cm1 to 400 cm1.

3. RESULT AND DISCUSSION

Fig. 1 show FTIR spectrum of Sr3MgxNi2-xFe24O41 Z-type Hexaferrite heated at 1250 °C recorded in the mid IR range (4000 cm1 to 400 cm1). A small amount of Sr3MgxNi2- xFe24O41 powder mixed with KBr powder and made in the form of a pellet for measurement. FTIR-spectrum of a power shows the characteristic bands have appeared at about 3440 and 2924 cm-1. These bands are assigned to be hydroxyl group [3, 4].

The IR spectra of all hexaferrites show the two principle absorption bands in the range of 438-443 cm-1 and 606-610 cm-1. These two vibration bands Fe-O and M-O are corresponded to the intrinsic lattice vibrations of octahedral and tetrahedral coordination compounds respectively [5, 6]. The normal mode of vibration of tetrahedral cluster is higher than that of octahedral cluster. The change in the band position is due to the change in the Fe3+- O2 internuclear distances for the tetrahedral and octahedral sites [79]. The band positions are listed in Table 1. Variation in the v5 with increasing Mg2+ also due to the modified distribution of cations that present in B sites because of Fe or Ni ions replaced with Mg2+ ions at B site. Bands observed around 912 attributed to the stretching vibration of Sr-O. This band gives the confirmation of formation of a Strontium ferrite. [10]. The frequencies of the band near about 988 cm-1 was found to be increasing with increasing Mg2+ content. The absorption frequencies are depends on the mass of the atom along with strength and angle of connecting bands [11]. The atomic weight of the Mg2+ is smaller (24.31 g/mol) than that of the Ni2+ (58.70 g/mol). The absorption frequencies increase with decreasing atomic weight. Thus the band at about 988 cm-1 was due to the atomic weight of the substituted Mg2+. The band around 1026 cm-1 was attributed to the Fe-O bending [12]. The broad band in the region 850 cm-1 to 1300 cm-1 was associated with the complex crystalline nature of the z-type hexaferrite. Shoulders were observed for all the Mg2+ substitution evidenced for the presence of Fe2+ ions in the samples formed during the sintering process. The intensities of the band depend on the ionic replacement and as a result on the magnetic dipole moment. Variation was observed in the intensities of the bands

Fig.1. FTIR spectra of Mg2+ substituted Sr3Ni2-xMgxFe24O41 hexaferrite for x

= 0, 0.2, 0.4, to 2.

with diamagnetic Mg2+ substitution for Ni2+. Such substitution causes change in the magnetic dipole moment with the inter-nuclear distance, affects the intensity E of the absorption band [5].

Teble1. Absorption frequencies of Sr3Ni2-xMgxFe24O41 hexaferrite with Mg2+ concentration

CONCLUSION

FTIR spectrum of Sr3MgxNi2-xFe24O41 Z-type hexaferrite prepared by standard ceramic method heated at 1250 °C was recorded in the mid IR range (4000 cm1 to 400 cm1) successfully. The band position obtained in the spectra at about 441 cm-1 and 609 cm-1 attributed to the vibration of octahedral and tetrahedral cluster in the hexaferrite respectively. Sr-O bond at about 912cm-1 was conformed the formation of strontium hexaferrite. Broad nature of the absorption band observed in the spectra ilustrated the complex nature of the Z-type hexaferrite. Shoulders observed

in the spectra evidenced for presence of Fe2+ in the hexaferrite for every substitution. Variation in the intensities of absorbed bands attributed to the change in the dipole moment with Mg2+ substitution.

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