Improving conductivity of apatite-type lanthanum silicate by Nd and Zn co-doping

Abstract The electrical properties of apatite-type lanthanum silicate co-doped with Nd and Zn has been investigated. The Nd and Zn co-doped lanthanum silicate, La9.33NdxSi6-yZnyO26+(3x/2)-y (0 ≤ x ≤ 1, y = 0,1), are successfully synthesized by the urea nitrate combustion method. The phase, morphology and electrical properties are characterized by X-ray diffraction, scanning electron microscopy and electrochemical impedance spectra, respectively. La9.33NdxSi6-yZnyO26+(3x/2)-y ceramics has good apatite structure and high purity. The conductivity of La9.33NdxSi5ZnO25+(3x/2) first increases and then decreased accompanying with Nd content increasing, which higher than that of undoped La9.33Si6O26. The increase of the conductivity, which is attributed to Zn doped introduces oxygen vacancies and expands oxygen ions migration channel as well as Nd doped decreases the defect centers and increases the amount of interstitial oxygen ions. The decrease in conductivity is due to excess Nd blocking the oxygen ions migration channel. La9.33Nd0.8Si5ZnO26.2 exhibited the highest conductivity which values equal to 8.11 × 10−4 S cm−1 at 650 °C.