Theoretical Studies On Inhibition Mechanisms Of Silver Agglomeration In Low-emissivity Coated Glass

With the rapid development of the construction industry,Chinese energy consumption of building has significantly increased year by year,which is accounted for a major proportion of the total human energy consumption and has reached 32%of the total social energy consumption.In the main consumption of building energy,the energy loss caused by glass doors and windows is accounted for about 40%of the total energy consumption of the building.In recent years,the research of the Low-E glass was used in modern buildings to meet the demand of energy saving application.Ag film can be used for the coat of Low-E glass.However,it should be noted that the silver film deposited on the dielectric oxide substrate is prone to agglomeration when heated,which thereby increases the resistivity of the silver film,affects its function and long-term service,and limits its scope of application.In recent years,many attempts have been done to suppress the high-temperature agglomeration of Ag films in academia and industry,but there is still a long way to go before the goal of fully revealing the mechanism of agglomeration inhibition.Therefore,this paper intends to research and discuss about the mechanisms of Ag film agglomeration inhibition in low-emission coated glass from the atomic level.In this paper,based on the density functional theory,some basic properties of several Ag-Ti intermetallic compounds were studied.Then focused on the the effects of AgTi₃ precipitated phase on suppression of Ag agglomeration,a series of related exploratory studies were carried out.The adsorption and diffusion of noble metal Ag atoms on AgTi₃ and Ti surfaces were examined.Based on this,I also examined the influence of the introduction of AgTi₃ on the optical applications of low-E glass.For the purpose of analogy study,the basic properties of the AgCu₃ alloy and the corresponding adsorptions as well as diffusion behavior of Ag atoms on different surfaces of AgCu₃were also discussed.The effects of AgTi₃/AgCu₃ precipitated phase on suppression of Ag agglomeration were calculated.The main results are as follows:First,the formation enthalpy,electronic structures and mechanical properties of several Ti-Ag intermetallic compounds were investigated by employing first-principles plane wave pseudopotential method.The formation enthalpy for AgTi₃ alloy is the highest among the considered three compounds,suggested that it is difficult to form AgTi₃ alloy.This result explains the reason for the absence of AgTi₃ in the stable phase of the Ti-Ag phase diagram.The calculation of its electronic properties showed that the energy bands near the Fermi level mainly come from Cu-d and Ag-d bands,AgTi,AgTi₂and AgTi₃ all have metallicity,and the conductive performance order is AgTi₂>AgTi₃>AgTi.Calculated mechanical properties suggested that all three intermetallic compounds show mechanical stabilities and excellent ductilities.First-principles calculations were carried out to examine the adsorption configurations for stable atoms with differences in coverage,surface diffusion,interfacial adsorption,separation and optical properties of noble Ag atoms,as well as Ag layers on AgTi₃ and Ti surface.All the Ag adatoms could occur in chemical adsorption on AgTi₃ and Ti surfaces.However,the diffusion of Ag atoms on AgTi₃ surfaces especially for AgTi₃（111）is much more difficult than on the Ti surface.Therefore,it can be reasonably concluded that AgTi₃phase would effectively suppress the agglomeration of Ag atoms.The results of the positive interface separations revealed that the combination of Ag（111）/AgTi₃（111）interface is thermodynamically stable,and the calculated results of optical properties indicated that the optical performance of Ag film would be barely negatively affected after the addition of AgTi₃ layer,implying an important applications of infrared absorption and reflection for the optical elements.In addition,the structures,electronic properties and mechanical properties of the AgCu₃ and Ag₃Cu intermetallic compound were also examined.The calculated electronic properties indicated that the conductive performance order is Ag₃Cu>AgCu₃.The analysis of mechanical properties proved that AgCu₃ has mechanical stability and good ductility.The results of the adsorption and diffusion of Ag atoms on AgCu₃（112）and AgCu₃（100）sufaces revealed that all these Ag atoms can be chemically adsorbed on AgCu₃（112）and AgCu₃（100）surfaces.The corresponding diffusion barriers of Ag atoms on AgCu₃（112）and AgCu₃（100）surfaces are-0.48e V and-0.43e V,respectively,which are significantly lower than that of the AgTi₃（111）surface（0.79e V）and AgTi₃（110）surface（1.18 e V）,implying that the Ag atoms are easier to diffuse on the AgCu₃ surface than that the AgTi₃ surface.That is to say,the effects of AgCu₃precipitated phase on suppression of Ag agglomeration is not as ideal as that of the AgTi₃ phase.This result confirmed the adulteration of Ti element in the Ag film can produce a good effect on the suppession of Ag film agglomeration.