Effect of Cerium on Structural and Dielectric Properties of Modified BiFeO3-PbTiO3 Ceramics for Photovoltaic Applications

In this communication, the cerium (Ce) modified (Bi0.4Fe0.4)(Pb0.6Ti0.3Ce0.3)O3 (BF-PT) ceramics is prepared by conventional solid-state reaction technique. The compound is found to crystallize in the rhombohedral crystal system with space group R-3c (#167). The refined lattice parameters are a = b = 4.989 A, c = 17.062 A, $$\alpha = \beta = 90^{^\circ } , \gamma = 120^{^\circ }$$ , V = 367.78 A3 and $$ \rho = 2.71$$ g/cm3 (JCPDS No.-00-005-0586). The average crystallite size and lattice micro-strain in the ceramics are estimated at 47.6 nm and 0.117% respectively. Scanning electron microscopy analysis indicates low porosity and well-defined grain boundaries, with an average grain size of 13.7 μm. Raman spectroscopy confirms the presence of all constituent elements and ferroelectric character. Ultraviolet–visible (UV–Vis) spectroscopy analysis suggests a bandgap of 1.72 eV for the modified BF-BT ceramics, which is suitable for photovoltaic applications. The study of complex impedance suggests a Cole–Cole-type relaxation with a decrease in bulk resistance from 6.283 × 1013 Ω cm2 at 25°C to 1.783 × 104 Ω cm2 at 500°C, confirming the negative temperature coefficient of resistance. The calculated activation energies are 849.8 meV, 706.5 meV, 575.1 meV, and 499.4 meV at 1 kHz, 10 kHz, 100 kHz, and 1000 kHz, indicating ionization of oxygen vacancy and the involvement of the released electrons in the hopping conduction process, and support a thermally activated conduction mechanism. The increase in the peak frequency difference between the $$ Z^{{{\prime \prime }}}$$ and $$M^{{{\prime \prime }}}$$ spectrum with temperature suggesting a non-Debye-type relaxation in the material. The material is characterized to a high dielectric constant and low tangent loss suitable for optoelectronic devices.