Physical and Electrical Properties of Nanosized Mn‐ and Cr‐Doped Strontium Y‐Type Hexagonal Ferrites

Abstract

Nanometer‐sized crystallites of Y‐type strontium hexaferrite, Sr2Ni2Fe12O22 and its Mn‐ and Cr‐doped derivatives have been synthesized by the sol–gel method. Y‐type phase formation was achieved at a considerably lower temperature of 950°C than is required in the traditional solid‐state method (1200°C). The effect of doping of manganese at the tetrahedral site, Sr2Ni2−xMnx Fe12O22 (x=0.0–2.0), and chromium at octahedral site, Sr2Ni2 Fe12−yCryO22 (y=0.0–1.5), has been studied. The crystal structure remains unaffected by the substitutions. The crystallite size in the range of 13–45 nm is calculated from the X‐ray diffraction data. The energy‐dispersive X‐ray fluorescence analysis shows that Y‐type hexaferrites can be prepared with a base of strontium. The extent of doped Cr+3 ions at the octahedral site has been increased from the reported maximum value of y=1.5. Scanning electron micrographs of the samples showed a homogenous microstructure. The dc electrical resistivity studies show that these hexaferrites exhibit high resistivity at room temperature. Cr‐doped samples have comparatively higher resistivity than Mn‐doped samples. The doubly doped (Cr+Mn) samples possess high resistivity (7.37 × 109Ω‐cm), a low dielectric constant (33.88 at 3000 Hz), and a high Curie temperature (>698 K). The dielectric energy losses are minimized by increasing the Mn and Cr contents of the synthesized samples.