Study On Preparation And Performance Of Room-Temperature BFO And GFO Based Multiferroic Films Based On Mica Substrate

Multiferroic materials are new multifunctional materials which simultaneously possess two or more ferroic order of(anti)ferroelectric,(anti)ferromagnetic,and ferroelastic.They have great application promise for sensors,high-density storage,energy converters,and microwaves.Among these,0.86Bi Ti_0.1Fe_0.8Mg_0.1O₃-0.14Ca Ti O₃(BTFM-CTO)solid solution material is room-temperature single phase multiferroic materials,which can enhance its piezoelectric performance at morphotropic phase boundary.The doping of B-site cations with elements such as Ti and Mg can stabilize the structure of Bi-based perovskite and enhance its magnetism and magnetoelectric coupling effect.Another new type of room-temperature single phase multiferroic Ga_0.5Fe_1.5O₃ material has ferrimagnetism and magnetoelectric coupling effect at room temperature.However,with the development of wearable and implantable electronic devices,there is a need for flexibility in room-temperature single phase multiferroic materials.Flexible multiferroic materials combine multiferroic properties with flexibility,which achieve multifield tunable ferroelectric polarization such as bending strain and magnetic field.Therefore,this dissertation will study the preparation and performance of Mica-based room temperature multiferroic films.In this dissertation,a room-temperature single phase multiferroic BTFM-CTO film was synthesized on Mica substrate by sol-gel and spin coating methods,and a room-temperature single phase multiferroic Ga_0.5Fe_1.5O₃ film was also prepared on Mica substrate by pulsed laser deposition(PLD).The specific research contents of this dissertation are as follows:(1)The room temperature multiferroic BTFM-CTO film was prepared on Mica substrate by the sol-gel and spin coating methods.The phase and topography test results showed that a high-quality BTFM-CTO film was synthesized.The BTFM-CTO film has ferromagnetic and ferroelectric at room temperature.Under the strain with a bending radius of 9 mm,the gradient strain induces flexoelectric field,which can exceed the coercive field of the polarization and result in the polarization switching,indicating that the bending strain switches the ferroelectric polarization of the BTFM-CTO film.Under the application of±5000 Oe in-plane magnetic field,the in-plane ferroelectric domain structure of the film also changed significantly,indicating that the BTFM-CTO film has obvious magnetoelectric coupling effect.room temperature multiferroic BTFM-CTO film can realize multifield switching ferroelectric polarization via magnetic field and bending stress.(2)The room temperature multiferroic Ga_0.5Fe_1.5O₃ film was prepared on Mica substrate by the PLD method.The phase and topography test results showed that Ga_0.5Fe_1.5O₃ film also was successfully prepared,which has the ferrimagnetic and ferroelectric performance at room temperature,its magnetic phase transition temperature is 383 K and the magnetic field can control the direction of magnetization.However,under the external magnetic field,the out-of-plane and in-plane ferroelectric domain patterns did not change,indicating that the external magnetic field fails to control the ferroelectric polarization of Ga_0.5Fe_1.5O₃ film due to large leakage current.