Phase Stability And Anti-reduction Sintering Of Magnesium Metatitanate Microwave Dielectric Ceramics

As a new kind of functional ceramics,microwave dielectric ceramics plays an irreplaceable role in the development of wireless communication technology.Microwave dielectric resonators that possess high quality factor?Q?and good temperature stability have become the key materials of the next generation 5G base station equipment.Therefore,this thesis used Mg_{?1.04–3/2y?}Ce_yTiO_3+?microwave dielectric ceramics as the research object,using traditional solid-phase method to prepare ceramic samples,besides,the phase structure and reaction model of MgO/TiO₂ ceramics were studied in detail.The influence of oxygen vacancy defects on the properties of the materials and the stability and reducibility of the phase components under different sintering atmospheres were investigated.Finally,a microwave dielectric ceramic material with good reduction resistance was prepared.Firstly,the structure and properties of MgTiO₃ ceramics were studied with different MgO raw materials and Mg chemical dosages,we inferred that the reaction process of MgO and TiO₂ is a core-shell structure.The MgO with the larger radius is the nucleus,and the TiO₂ with the smaller radius is the shell.During the reaction,TiO₂ surrounds the core MgO,and thus MgTiO₃ is formed,However,MgTiO₃ will hinder the further reaction between shell TiO₂ and nuclear MgO,so that TiO₂ and MgTiO₃ formed MgTi₂O₅.Then on the basis of the above,A-site doping of MgTiO₃ was performed.The structure and properties of Mg_{?1.04–3/2y?}Ce_yTiO_3+?ceramics were studied.It was found that Ce³⁺ions can replace Mg²⁺ions in small amounts.When y=0.01,microwave dielectric properties were the best.In addition,the temperature coefficient of resonant frequency of Mg_{?1.04?–3/2y}Ce_yTiO₃+?ceramics was controlled.When the molar ratio of CaTiO₃ is 0.08,the temperature coefficient of resonance frequency of?1-x?Mg_{?1.04–3/2y?}Ce_y TiO_3+?-xCaTiO₃ ceramics was nearly zero.XPS analysis of?1-x?Mg_{?1.04?–3/2y}Ce_y TiO₃+?-xCaTiO₃ceramics revealed that oxygen loss during the sintering process leads to the formation of oxygen vacancies,which led to the generation of electrons and the reduction of Ti⁴⁺to Ti³⁺,which in turn reduced the ceramic microwave dielectric properties.Finally,this thesis researched the stability of the phase composition of MgTiO₃ in different atmospheres?Air?O₂?N₂?and the effect of CeO₂ doping on the reducibility of the material were studied.As a result,it was found that the MgTiO₃ ceramic can maintain a stable phase composition under different atmospheres?Air?O₂?N₂?.However,the phase composition of Mg_{?1.04–3/2y?}Ce_yTiO_3+??y=0.01?ceramics in different atmospheres?Air?O₂?N₂?is different.Through XPS analysis,it was inferred that the oxygen partial pressure affects the solid solution of CeO₂ in MgTiO₃,the higher the oxygen partial pressure,the higher the Ce⁴⁺content,and from the perspective of the balance of electricity price,it can be seen that the less Ce⁴⁺required for the A site results in the precipitation of excess Ce⁴⁺with CeO₂.