High-performance　electro-optic　(EO)　materials　greatly　enhance　modulators　and　switches　in　various　photonic　applications.　We　investigate　the　evolution　of　the　tolerance　factor　(t)　and　EO　coefficient　(rc)　in　A-site　and　B-site　doped　BaTiO3　(BT)　thin　films.　Our　analysis　reveals　that　cation　transmutation　has　a　remarkable　impact　on　their　dielectric　constant,　spontaneous　polarization,　optical　band　gap,　and　EO　coefficient.　Notably,　Pb-doped　BT　samples　exhibit　an　even　higher　rc　value　of　336.5　pm/V,　representing　a　nearly　60%　increase　compared　to　pure　BT　and　approximately　11　times　larger　than　that　of　LiNbO3.　This　substantial　improvement　in　EO　performance　can　be　attributed　to　enhanced　local　structural　heterogeneity　resulting　from　cation　dopants.　Furthermore,　infusing　dopants　in　BT　also　result　in　good　structural　uniformity　and　reliable　EO　performances,　regardless　of　temperature　and　frequency.　Our　study　offers　valuable　insights　into　doping　engineering　for　obtaining　functional　perovskite　oxides,　enabling　the　development　of　power-efficient,　ultra-compact　integrated　nanophotonic　devices.　©　2024　The　American　Ceramic　Society.