Investigation of the Doped Alkaline Earth Metals in PbTiO3 Piezoelectric Ceramic Materials Based on the First Principle
The quantum mechanical square potential barrier model was applied to screen out three alkaline earth metal cations,Ca2+,Sr2+,and Ba2+,that can be doped into the Pb sites of PbTiO3 piezoelectric ceramic materials.Using the Materials Studio software,nine structural configurations of Pb1-xMxTiO3(x=0.037,0.074,0.111,where M=Ca,Sr,Ba)were constructed.The CASTEP module was used to perform geometric optimization of their structures and calculate their physical properties.As the doping amount of alkaline earth metals increasing,the results indicate that the crystal structure of doped Pb1₋xMxTiO3 is affected by the doped elements and the concentration,which determined the piezoelectric properties.The differences between the alkaline earth metal cations and Pb2+ions lead to p-type doping,and the bandgap exhibits a nonlinear downward trend.Notably,when x=0.074,Pb1₋xMxTiO3 transforms from a direct semiconductor material to an indirect semiconductor material.The Fermi level gradually decreases,and the conduction band minimum also changes with the doped elements and their concentrations,altering the interaction between electrons reflected by the"pseudo-gap".In summary,the doping of Ca2+,Sr2+,and Ba2+ affects the charge distribution within the material,thereby modulating its piezoelectric properties.
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