ساخت نانو ذرات فریت باریم جانشانی شده با یوروپیوم و بررسی خواص ساختاری و مغناطیسی آن

in this thesis, barium ferrite nano particles were prepared by sol-gel method. their structural and magnetic properties of samples have been investigated using thermo gravimetric analysis (tg-dta), x-ray powder diffractometer (xrd), fourier transform infrared (ftir), scanning electron microscopy (sem), field emission scanning electron microscopy (fesem), ac susceptometer, vibrating sample magnetometer (vsm) and vector network analyzer. at the first part, barium ferrite with pva prepared. in order to formation of this ferrite, it was used the stoichiometric of iron nitrate (fe(no3)3), barium nitrate (ba(no3)2), polyvinyl alcohol (c2h4o)n, citric acid (c6h8o7.h2o) and ethylenediaminetetraacetic acid or edta (c10h16n2o8). with the increase of temperature, there is no noticeable weightlessness in tg curve and the exothermic peak at the temperature of higher than 700?c in tg-dta curves indicating the formation of hexagonal phase. thus tg-dta curves indicated that the m-type hexagonal phase formation temperature decreases. this sample sintered at 700, 800, 900 and 1100 ?. the xrd patterns showed the pure hexagonal phase formed at 800 ?. the xrd patterns with rietveld analysis point to the formation of single hexagonal phase and p63/mmc space group. the crystallite size of samples was estimated to be about 40-70 nm by williamson-hall equation. these values are smaller than samples without pva. large particle agglomerations (with mean diameter of particles smaller than ) were observed in fesem images. ftir results showed that the ferrite has two specific bands in 438 and 600 cm-1 which former depend on octahedral sublattice and the latter corresponds to tetrahedral sublattice. the bounds have no displacement in samples with pva. in second part, the effect of composition on ba1-xeuxfe10.5o16.75 (x=0.0, 0.05, 0.1, 0.2, 0.25) synthesized to study the structural and magnetic properties. the xrd patterns with rietveld analysis point to the formation of single hexagonal phase and p63/mmc space group at 1100 ?. substituted samples have smaller crystallite size than pure one, which demonstrate the grain growth inhibitor role of eu. sem images indicated no differences among particle size of samples. it is found that there are large particle agglomerations, too. ftir results showed that the ferrite has two specific bands in 438 and 602 cm-1. there are not any bound displacement and europium bound in ftir spectra of substituted samples accordance with xrd. it is observed that real part of magnetic susceptibility has no change with increasing ac field and frequency at room temperature. susceptibility of samples with x doesn’t vary remarkably, too. the maximum enhancement in coercivity and minimum saturation magnetization was observed in the sample ba0.75eu0.25fe10.5o16.75. the hysteresis loops indicate that doping enhances coercivity and decreases saturation magnetization. the measurements of reflection loss were done at x and ku band frequency. we obtained higher reflection loss for x= 0.0 sample in the x-band and the ferrite with composition of x= 0.1 provides the best electromagnetic absorbing properties at ku-band frequency. thus substitution is useful to improve reflection loss at ku-band frequency while doping isn’t applicable to enhance the reflection loss at x-band frequency.