Pb-free semiconductor ferroelectrics: An experimental study of Ba(Ti_0.75Ce_0.125Pd_0.125)O_3-δ thin films

Thin films of perovskite-type Ba(Ti_0.75Ce_0.125Pd_0.125)O_3-δ (BTCPO) have been investigated by means of microstructural characterizations, optical and magnetic measurements. X-ray diffraction patterns show that the BTCPO exhibits a centrosymmetric cubic perovskite structure accompanied by the grain refinement. Raman spectroscopy, however, shows the symmetry of crystalline structures is locally lowered by the presence of dopants, significantly deviating from the ideal Pm3m space group, possibly due to an increased internal strain. The BTCPO film possesses a narrow bandgap of 2.21 eV, much smaller than BaTiO₃ (3.5 eV), which originates from new states in the electronic structure with the presence of Pd²⁺. Magnetic hysteresis loops indicate that the BTCPO film exhibits an excellent combination of saturation magnetization and coercivity at room temperature.