First-Principles Studies on the Properties of Si and Ce Doped Lanthanum Zirconate
Lanthanum zirconate is a new type of thermal barrier coating material,which provides heat insulation and cooling effect for the surface of high temperature parts of heavy gas turbine,aero-engine and hypersonic aircraft.Its thermal expansion coefficient is lower than that of yttrium stable zirconia,which does not match the thermal expansion coefficient of the bonding layer,and the fracture toughness is relatively low,resulting in the lack of good toughening mechanism of the material.Therefore,how to improve its thermal expansion coefficient and fracture toughness is a research hotspot in this field.Using density functional theory first-principles method to optimize lanthanum zirconate with silicon and cerium elements respectively.It is found that with the increase of Si doping content,the structural band gap widens,the elastic constant gradually increases,the structure still maintains brittle characteristics,the fracture toughness coefficient,the average sound velocity,Debye temperature and the lowest thermal conductivity gradually increase,and the thermal expansion coefficient gradually decreases.The Ce substitution showed the opposite trend.In general,Ce doping has better elastic modulus,minimum thermal conductivity and thermal expansion coefficient,and better fracture toughness for Si doping than pure lanthanum zirconate doping.
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