Synthesis And Magnetic Properties Of Substituted Ferrite Nanoparticles

Ferrites are important magnetic functional materials which are used in many fields. The synthesis of the powder has always been the subject of extensive studies. In this paper, the spinel ferrites and W-type ferrites were synthesized with different methods. The synthesizing conditions, structure and magnetic properties were groped. The structure was characterized by XRD, DTA, TG-DSC, SEM, TEM, FT-IR, and M(?)ssbauer. The magnetic properties were tested by VSM.The main contents of this thesis are as follows:1. A series of nanosize spinel ferrites of Zn_xFe_3-xO₄ and Ni_1xZn_xFe₂O₄ were synthesized by oxalate co-precipitation method. The results showed specific saturation magnetization(σ_s) of Zn_xFe_3-xO₄ has a maximum at x=0.4 for the ion substituent. Specific saturation magnetization(σ_s) of Ni_1-xZn_xFe₂O₄ has a maximum at x=0.45. The specific saturation magnetizations are all superior to the results of the other literatures.2. The influence of doping rare earth element on Zn ferdte and Ni-Zn ferfite structures and magnetic properties was discussed. The result indicated that specific saturation magnetization of ZnLa_xFe_2-xO₄ has a minimum at x=0.03. The specific saturation magnetization of ZnCe_xFe_2-xO₄ has a maximum at x=0.04. The specific saturation magnetization of Ni_0.55Zn_0.45Nd_xFe_2-xO₄ has a maximum at x=0.04,σ_s =70.25 A·m²Â·kg^-1.3. The W-type ferrites were synthesized by citric acid sol-gel method. The influences of pH, concentration, complex and calcining temperature were discussed. The ideal pH is 7～9. Concentration is that the nitrates of 0.005mol W-type ferrite were added into 150ml water. The amount of citric acid is that the ratio of amount of substance of citric acid and nitrates is 1.2: 1. The calcining temperature is 1000-1100℃.4. The mechanism of citric acid sol-gel method was extracted. The mechanism of citric acid sol-gel method consists of complex reaction and redox reaction. The mechanism of complex reaction can explain the resultant of gelate and the mechanism of redox reation can explain the process of ferrite powder.5. The influence of doping element onW-type ferrite structures and magnetic properties was discussed. The result showed that specific saturatior magnetizations of SrZn_2-xNi_xFe₁₆O₂₇ and SrZn_2-xCo_xFe₁₆O₂₇ increased and coercivity decreased all through with the increasing of x, specific residua magnetization had a maximum at x=0.4. Specific saturation magnetizations oJ Sr_1-xLa_xZn_1.6Ni_0.4Fe₁₆O₂₇ increased with the increasing of calcining temperature and coercivity had a maximum at 1000℃. Specific saturation and residua magnetizations of Sr_1-xCe_xZn_1.6Ni_0.4Fe₁₆O₂₇ had a maximum at x=0.2, coercivity decreased all through with the increasing of cerium.