Deposition And Properties Of Bismuth Magnesium Niobate Thin Films By Pulsed Laser Deposition

Issues related to the energy field have been widely concerned,such as energy development,utilization and energy storage.Common energy storage devices include supercapacitors,dielectric capacitors and fuel cells.Dielectric thin film capacitor has the advantages of long cycle life,high power density and small volume,which is easier to real ize the miniaturization of equipment.In this paper,two kinds of thin films with Bi _1.5Mg Nb_1.5O₇and Bi₂Mg_2/3Nb_4/3O₇ were prepared by pulsed laser deposition(PLD).Bismuth magnesium niobate(BMN)thin films have the advantages of low loss and high tunability.This paper aims to study the process parameters in the preparation process,measure the effect of different process parameters on the properties of BMN thin films by means of X-ray diffraction,atomic force microscope,X-ray photoelectron spectroscopy and impedance analyzer,and finally obtain the optimal process parameters in a certain range,so as to optimize the properties of BMN films.The main research contents and results of this paper a re as follows:(1)Bi_1.5Mg Nb_1.5O₇ thin films were prepared on ITO substrates by PLD.The first is to study the effect of substrate temperature on the structure and electrical properties of the films.The results show that the dielectric constant,tunability and energy storage density of the films increase first and then decrease with the increase of substrate temperature.The Bi_1.5Mg Nb_1.5O₇ thin film prepared at 100?has the best comprehensive properties.Then,based on the study of substrate temperature,the effects of deposition at 100?and annealing in the temperature range of 200??600?on the properties of the films were studied.The FOM value of the films annealed at higher temperature is about three times that of the films annealed at low temperature.The energy storage density of BMN thin films annealed at 600?is about three times that of other films,so the properties have been significantly improved.Based on the parameters of substrate tem perature and annealing parameters,the BMN films deposited at 100?and annealed at 600?have the best properties in the range.At this time,the dielectric constant of the film is 204,the loss is 0.009,the tunability is 13.1%,and the energy storage density is 0.144 J/cm~3.(2)Bi₂Mg_2/3Nb_4/3O₇ thin films were prepared on ITO substrates by PLD.Firstly,the effect of substrate temperature on the properties of Bi₂Mg_2/3Nb_4/3O₇was studied.The results show that the energy storage density,FOM value and dielectric constant of Bi ₂Mg_2/3Nb_4/3O₇ films are improved with the increase of temperature.The bismuth magnesium niobate films prepared at 150?have excellent comprehensive properties.Based on the study of substrate temperature,the effect of oxygen pressure on the properties of the films w as studied.XRD,AFM and XPS analysis show that oxygen pressure ha s an effect on the morphology and internal structure of Bi₂Mg_2/3Nb_4/3O₇ thin films.With the increase of oxygen pressure,the tunability and energy storage density of the film first decrease and then increase.At 10 Pa,the film has the best dielectric and energy storage properties.Under 10 Pa oxygen pressure,the dielectric constant of the film is 138,the loss is 0.0043,the tunability is 16%,and the energy storage density is 0.0749J/cm~3.