Effect of co doping on the electric and dielectric properties of Bi3.8−xEr0.2YbxTi3O12 lead-free ceramics

•Yb doping of Bi4Ti3O12 reduces its conductivity and makes it suitable an insulator for capacitor working at high temperature.•Doping of Bi4Ti3O12 by both Er and Yb doesn’t alter crystallographic structure and phase formation.•Co-doping of Bi4Ti3O12 by Er and Yb offers new optical applications.•Co-doping of Bi4Ti3O12 by Er and Yb increases the permittivity and reduces the loss factor temperature and frequency. The development of novel lead-free materials operating at high temperature and able to replace lead-based compounds and their derivatives in different devices is currently a remarkable challenge. In spite of having a high Curie temperature, the ferroelectric Bi4Ti3O12 is rarely used as a piezoelectric due to its high conductivity. In this work, Bi ions in Bi4Ti3O12 were partially replaced with Yb and Er aiming to compensate oxygen vacancies and improve others physical properties. In particular, Bi3.8−xEr0.2YbxTi3O12 compounds with x = 0.05, 0.1, and 0.2 were prepared by a low-cost solid-solid state reaction process, and their structural, optical and electrical properties were investigated. It was observed that, at low temperatures, the conductivity, impedance and permittivity are mainly governed by grain effects, and by grain boundaries and grains effects at high temperatures. The electrical conductivity at 700 K decreases with Yb content and shows a minimum for x = 0.2. The relative permittivity at high temperatures is colossal while the tangent loss is negligible. High permittivities accompanied with low loss factor were obtained for Bi3.6 Er0.2Yb0.2Ti3O12. These results open a wide application domain for this particular compound.