Semiconducting behavior of CaO-added BaTiO3-(Bi1/2Na1/2)TiO3 solid solution ceramics

We report synthesis of BaTiO3-(Bi1/2Na1/2)TiO3 (BT-BNT) semiconducting ceramics by conventional solid-state reaction method in air atmosphere. By adding CaO into the calcined BT-BNT powder, the resulting ceramics acquires the semiconductivity with the resistivity at room temperature ρRT value of 10²–10³ Ωcm and PTC behavior. The structure analysis using X-ray diffraction method, it was found that the CaO added BT-BNT ceramics consisted of perovskite-type ABO3 single phase. Chemical composition analysis by inductively coupled plasma spectrometry disclosed a distinct evaporation of Na and Bi during sintering process. The quantity of evaporation of Na was higher than that of Bi. Based on these results, it was suggested that dominant substitution of Ca²⁺ for Na⁺ in the A site occurred, and then that part of Bi³⁺ separated from divalent (Bi1/2Na1/2)²⁺ pairs worked as a donor.