Study On Preparation,diffusion And Properties Of MnF₂ Doded ZrO₂

Zirconia materials have high application and research potential in ceramics because of their excellent physical and chemical properties,such as high strength,high hardness,high toughness,extremely high abrasion resistance and chemical resistance.There are three structural polymorphisms in zirconia?ZrO₂?:monoclinic phase?m?,tetragonal phase?t?and vertical direction?c?.As the temperature increases or the appropriate dopant is added,a phase change from monoclinic to tetragonal and cubic occurs.At room temperature,many doping materials with different valences can be used to stabilize the high-temperature tetragonal or cubic phases of ZrO₂.Excellent properties such as excellent ionic conductivity,high hardness,and high dielectric constant could be realized by chemical modification.The goal of this paper is to study the basic physical properties,phase transition behaviors,stabilization mechanism and analyze its application prospects in the industrial field.The thermodynamic and kinetic studies on the phase formation of MnF₂-ZrO₂system were carried out for the first time.The mechanism of stabilizing effect of polyvalent element Mnon ZrO₂was elaborated.Furthermore,the reaction model of Mn-Zr-O-F system was established.Then on the base of these,the optical,electrical and magnetic properties of the system were studied.The main findings are as follows:?1?Firstly,based on the thermodynamic experiments of MnF₂-ZrO₂system,the system's thermodynamic stable phase and the factors on the phase transition were systematically analyzed using TG-DSC.DSC results show that MnF₂-doped ZrO₂undergoes the decomposition of MnF₂,the phase transition of m-ZrO₂?t-ZrO₂,and the entry of Mn²⁺into the t-ZrO₂lattice and the formation of c-ZrO₂solid solution process.By comprehensively analyzing the parameters that affect the phase transition process,the phase transition mechanism of MnF₂doped ZrO₂is proposed.Phase stability studies have found that the cubic phase can still exist stably when zirconia with a cubic phase is annealed at different temperatures in an argon atmosphere.The cubic phase below 800?can exist stably when annealed in an air atmosphere.Cubic zirconia transforms into monoclinic zirconia when the temperature reaches 1000?.?2?The MnF₂-doped ZrO₂diffusion couple method was used to study the diffusion process of the elements and the growth mechanism of the diffusion product phase.Mnelement is the main diffusive substance during the diffusion process.It diffuses into the m-ZrO₂lattice to form a c-ZrO₂solid solution during the diffusion process.By studying the growth law of the interaction layer of c-ZrO₂,it is concluded that the growth mechanism is lattice diffusion controlled growth mechanism.?3?The MnF₂doping leads to a decrease in the bandgap.A blue shift in the the fluorescence emission peak as the doping concentration of MnF₂increases,accompanied by the enhancement of the strength.In the meanwhile,the MnF₂doped ZrO₂samples shows improvement in the degradation ability of MB dyes.?4?The conductivity of MnF₂doped ZrO₂samples with different concentrations increases with the increase of MnF₂doping concentration,accompanied by the decrease in the activation energy.After annealing in argon and air,the electrical conductivity of the 30mol%MnF₂doped ZrO₂samples increases and the activation energy decreases with the annealing temperature.The activation energy decreases sharply when the annealing temperature reached at 1000?.?5?The magnetic properties of MnF₂-doped ZrO₂samples originates from the interactions between defects and oxygen vacancies in cubic ZrO₂lattices.The magnetic enhancement is related to the increase in the oxygen vacancies by Mndoping.Despite the decrease in the magnetic moment,the ferromagnetic interaction is still present in the 30mol%MnF₂doped ZrO₂samples after annealing.