**2. Materials and Methods**

Fabrication: CBTi-BFO films were synthesized on Pt/Ti/SiO2/Si substrates by chemical solution deposition. Bismuth nitrate pentahydrate [Bi(NO3)3·5H2O], calcium nitrate tetrahydrate [Ca(NO3)2·4H2O], iron nitrate nonahydrate [Fe(NO3)2·9H2O], manganese acetate tetrahydrate [C4H6MnO4·4H2O] as raw materials were dissolved in ethylene glycol and acetic acid. Here, 10 mol% excess Bi was added to compensate for elements volatilization. After that, the tetrabutyl titanate and acetylacetone were added into the mixed clarified salt solution. The final concentration of the precursor solution was 0.1 M. After 24 h of aging, the precursor solution was spin coated on Pt/TiO2/SiO2/Si substrates with a speed of 4000 rpm for 30 s. After that, the as-prepared CBTi-BFO films were pyrolyzed at 350 ◦C for 120 s and annealed at 450, 500, 550, 600 ◦C for 10 min in a rapid thermal annealing procedure, respectively. The spin coating and annealing process procedures were duplicated up till the desired thickness of 300~700 nm was obtained. Circular Pt top electrodes, ~200 μm in diameter, were sputtered through a shadow mask on the films for the next electrical measurements.

Characterization and Measurements: The crystalline structure of CBTi-BFO films was characterized by an X-ray diffractometer (XRD) with Cu K*α* radiation (XRD, D8 ADVANCE, Karlsruhe, Germany). The cross-sectional microstructure and surface morphology were characterized by a field emission scanning electron microscope (FESEM, ZEISS Gemini300, Oberkochen, Germany). The polarization-electric field (*P-E*) loops and insulating characteristic were acquired from a standard ferroelectric tester (aixACCT TF3000, Aachen, Germany). The frequency-dependent dielectric properties and impedance data were measured using impedance analyzer (HP4294A, Agilent, Palo Alto, CA, US). Impedance data were analyzed by a Z-view software. The temperature-dependent electrical performance tests were completed with the help of a temperature-controlled probe station (Linkam-HFS600E-PB2, London, UK).
