Preparation And Application Of Textured Z-Type Hexagonal Ferrites Materials

Z-type hexagonal ferrites are regarded as promising candidates for high frequency materials and magneto-electric materials.But it is difficult to synthesize single phase hexagonal ferrites of Z-type by traditional methods.Hydrothermal synthesis method possess advantages of the high reactivity of reagents,feasibility of difficult reactions,great control on particle size and the production of phase pure and homogeneous materials.However,there is little report on synthesis Z-type hexagonal ferrite by hydrothermal method.In this dissertation,hydrothermal synthesis method was used to prepare Z-type hexagonal ferrites.The technological conditions of two main steps which include synthesis precursor by hydrothermal and high-temperature calcination were studied systematically in this work.Moreover,the texturing property of Z-type materials was studied.This paper contains the followings:1.The effects of hydrothermal synthesis conditions on the phase composition and micro-morphology of the precursor and Z-type ferrite were investigated,and the optimum hydrothermal reaction temperature T_h and reaction time th were defined.It was observed that Z-type ferrites with extra impurity phases were formed when T_h?280°C.And the condition of T_h=300°C lead to form Z-type with little impurity.Under the condition of T_h=300°C,Z-phase can be formed when t_h?20 h,while the impurity phase is less at t_h=36 h.2.The effects of mole ratio of hydroxide ion to nitrate ion(R^--_OH/NO3=3y:1)and mole ratio of cerium ion to iron ion(R²⁺³⁺_Sr/Fe=x:8)on the phase composition and micro-morphology of the precursor and Z-type ferrite were investigated,and the optimum x and y were defined.The Z-phase can be formed when 0.4?y?1.2,and the Z-phase is relatively pure when y=0.8.And the Z-phase can be obtained when x?1,and when x=2.0,2.5 or 3.0,Z phase with little impurity phases were formed.3.The effects of precursor calcination temperature T_c and calcination time t_c on the composition,morphology and magnetic properties of the Z-type ferrite were investigated.The optimum T_c and t_c were defined.Z-type ferrite were indexed as a major phase with little impurity phase when T_c=1150¹200°C,while the ferrites were pure when T_c=1185°C and 1200°C.Under the condition of T_c=1185°C,single Z-type hexaferrite phase without extra impurity phases was detected when t_c is more than 2h.4.The effect of oxygen atmosphere calcination on Z-type hexagonal ferrite was investigated.Experiments show that the oxygen atmosphere calcination has no effect on Tc or the material phase composition,but it changed the texturing property of Z-type materials,the grain orientation was not?0 0 l?any more.5.The texturing property of Z-type materials was investigated.It was found that the Z-type materials formed by sintering schistose precursor has texturing in direction of?0 0 l?.Then we prepared textured Z-type ferrite via tape-casting method,but the ferrites did not texture well.6.Antenna simulation with Z-type hexagonal ferrite.