The Study Of Barium Strontium Titanate (Ba_1-xSr_xTiO₃) Films With Dielectric Properties And Flexoelectric Coefficients

Barium strontium titanate?BST?is a common ferroelectric material.It is widely in the field of sensor applications because of its prominet properties,such as high dielectric constants,piezoelectric constants and flexoelectric coefficients.The electronic components develop toward lighter and thinner one with the rapid updating of science and technology,so it is important to study the BST films.The BST films are prepared by Sol-Gel method and which is also applied for preparing two kinds of composite films with parallel structure,BST/ZrO₂ composite films and BST/MgO composite films.So this article puts comes up with an idea about two film capacitors in parallel to improve the dielectric constant and flexoelectric signal.The main concerns are BST films' dielectric properties and flexoelectric coefficients influenced by different preparation processes as well as composite films' dielectric properties and flexoelectric coefficients influenced by different non-functional layers and electrode layers.It is found that stable BST sols,ZrO₂ sols,MgO sols and La1-xSrxCO3?LSCO?sols can be prepared by Sol-Gel method.The spin coating method is used to prepared BST films,BST/ZrO₂ composite films and BST/MgO composite films on the Si/SiO₂/Ti/Pt base.The changes of Y³⁺-dopes concentration,annealing conditions and pH value of BST sols would improve the surface microstructure to enhance the dielectric constants and flexoelectric coefficients of BST films.It is concluded that BST films have the relatively optimized dielectric cconstants?dielectric constants 409;dielectric loss 0.0104?,flexoelectric coefficients?transverse flexoelectric coefficients 0.83?C/m?and equivalent piezoelectric constants?10.67×104?C/N?when the pH value of BST sols is 4.1 and BST films(1mol%Y³⁺)annealed in 800? for 15 min.The BST/ZrO₂ composite films and BST/MgO composite films with different annealing temperatures are prepared by Sol-Gel method on the same bases.It is found that the dielectric properties and flexoelectric coefficients varied with the surface microstructure of composite films.The BST/Zr O₂ composite films have the optimized dielectric constants?dielectric constants 790;dielectric loss 0.0510?,flexoelectric coefficients?transverse flexoelectric coefficients 1.50?C/m?and equivalent piezoelectric constants?19.82×104?C/N?when the annealing temperature is 750?.The BST/MgO composite films had relatively optimal integrated performance in the same annealing temperature,which dielectric constants?dielectric constant 800,dielectric loss 0.0412?,flexoelectric coefficients?transverse flexoelectric coefficient 2.00?C/m?and equivalent piezoelectric constants?25.10×104?C/N?are relatively highest.It is also compared that the dielectric properties of composite films influenced by two kinds of electrode layers?Au films and LSCO films?.Different electrode layers have little effect on the surface microstructure and dielectric properties of composite films when the annealing temperature are under 750?.The composite films with the LSCO electrode layers have better surface microstructure and dielectric constants when the annealing temperatures are above 750?.Composite films have optimized dielectric constants?804 of BST/ZrO₂ composite films,816 of BST/MgO composite films?and minimum dielectric?0.0467 for BST/ZrO₂ composite films,0.0373 for BST/MgO composite films?loss when the annealing temperature is 800?.The dielectric properties of composite films were decreased when the annealing temperature are above 800?.