Preparation Of Nickel Zinc Ferrite By Cold Sintering And Its Magnetic And Electrical Properties Investigation

With the development of information technology,the multi-function and miniaturization of electronic devices have become an inevitable trend,which provides an opportunity for the rapid development of ferrite materials.Ni_0.5Zn_0.5Fe₂O₄（NZFO）,as a multifunctional material integrating inductance and capacitance,not only has excellent electrical properties such as high resistivity and high dielectric constant,but also has excellent magnetic properties such as high permeability and high saturation magnetization,which can effectively reduce the material consumption and device size.It is widely used in a wide range of modern technologies and electrical appliances,including telecommunications,sensors,and biomedicine.The conventional solid-phase sintering method for the preparation of NZFO materials requires high temperatures,which makes it difficult not only to control the morphology,but also consumes a lot of energy and generates heterogeneous phases that weaken the material properties.Therefore,this topic takes NZFO and its composite materials as the research object,adopts the method of cold sintering,and starts with the optimization of experimental process parameters and component design to study the structure,electrical,and magnetic properties of materials in detail.The main findings are as follows:（1）Cold Sintering Preparation and Properties of Ni_0.5Zn_0.5Fe₂O₄（NZFO）:To investigate the effect of liquid content（0%,2.5%,5%,7.5%,10%）in cold sintering on the density and properties of NZFO ceramic samples,the precursor was prepared using the chemical coprecipitation method.The results show that as the liquid phase content increases,the relative density of NZFO ceramic samples increases and then decreases.When the liquid phase content is 7.5%,the maximum density is 73.53%,and the saturation magnetization and dielectric constant at 100 Hz also reach the maximum value,which are 53.31 emu/g and 179.45,respectively.Direct cold sintering sample density is limited;we cold sinter after further annealing treatment（500℃,700℃,900℃,1100℃）.XRD and SEM show that the average grain size increases with the increase in annealing temperature,and the relative density also increases.The maximum grain size is 97.02%at 1100℃,and the maximum dielectric constant at 100 Hz is 79.28 emu/g and 583.96,respectively.Higher than conventional sintering at 1100℃（76.18 emu/g and 505.44）.These results indicate that the cold sintering process has great research value for improving the performance of NZFO ceramic materials.（2）Preparation and properties of Ni_0.5Zn_0.5Fe₂O₄-Na₂Mo₂O₇（NZFO-NMO）composite ceramics by cold sintering:The（1-x）NZFO-x NMO（x=0,0.2,0.4,0.6,0.8,1.0）composite ceramics were prepared by the cold sintering process using the NZFO powder prepared by the chemical coprecipitate method and Na₂Mo₂O₇（NMO）powder prepared by the solid sintering method as raw materials and distilled water as the liquid phase.XRD results show that there is no chemical reaction between NMO and NZFO after cold sintering,and the microstructure is uniform and compact.For 0.8 NZFO-0.2 NMO multiphase ceramics,the dielectric constant and dielectric loss are 111.99（@100 Hz）and 0.40（@100 Hz）,respectively.The resistivity and saturation magnetization are 8.04×10⁴Ω·m and 36.52 emu/g,respectively,showing low loss and high magnetoelectric performance.It is expected to be used in device miniaturization.（3）Preparation and properties of NZFO-PEEK composite ceramics by cold sintering:To investigate the effect of changing the polymer phase content on the properties of composite ceramics,a series of（1-x）NZFO-x PEEK（x=0,0.1,0.2,0.3,0.4）composite ceramics were cold sintering with glacial acetic acid as the liquid phase.XRD results showed that PEEK and NZFO did not react with each other,resulting in no heterophase.When PEEK content was high,two weak peaks belonging to PEEK could be seen.SEM results show that the microstructure is uniform and compact.For0.9 NZFO-0.1 PEEK multiphase ceramics,the dielectric constant and dielectric loss are 34.99（@100 Hz）and 2.83（@100 Hz）,respectively.The resistivity and saturation magnetization are 7.59×10⁵Ω·m and 47.90 emu/g,respectively.This study may inspire further research on the preparation of ceramic-polymer composites by cold sintering method,in addition to the preparation of composites with low loss and high magnetoelectric properties.