TY - JOUR
T1 - Perovskite-type metal oxides exhibiting negligible grain boundary resistance to total electrical conductivity
AU - Pannu, Tania
AU - Pannu, Kanwar Gulsher Singh
AU - Thangadurai, Venkataraman
PY - 2011/1/17
Y1 - 2011/1/17
N2 - In this paper, we report the synthesis, structure and electrical properties of the perovskite-type AZn0.33+xNb0.67-xO 3-δ (A = Sr or Ba; 0 ≤ x ≤ 0.08). The investigated compounds were prepared by employing the solid-state (ceramic) reaction using alkaline nitrates, zinc oxide, and niobium oxide at elevated temperatures in air. Powder X-ray diffraction (PXRD) showed the formation of disordered Zn and Nb at the B-sites of space group Pm3̄m with cubic structure and a lattice constant comparable to that of the literature. The AC impedance study showed mainly bulk contribution to the total electrical conductivity over the investigated frequency range of 0.01 Hz to 1 MHz in all the investigated atmospheres even at low temperatures, which is significantly different from that of the well-known perovskite-type B-site ordered BaCa0.33+xNb 0.67-xO3-δ and the disordered acceptor-doped BaCeO3. The bulk dielectric constant determined at 500 and 700 °C in air was found to be in the range of 35-100. In air, the isothermal bulk dielectric constant seems to increase with an increasing Zn content, and a similar trend was observed for total electrical conductivity. In dry and wet H2, the electrical conductivity decreases with an increasing Zn content in AZn0.33+xNb0.67-xO3-δ, and the x = 0 member of the Ba compound exhibits the highest total conductivity of 7.2 - 10-3 S cm-1 in dry H2 at 800 °C. Both Sr and Ba compounds were found to be stable against the reaction with pure CO 2 at 700 °C and H2O at 100 °C for a long period of time. SrZn0.33+xNb0.67-xO3-δ was found to be stable in 30 ppm H2S at 800 °C, while the corresponding Ba compound formed reaction products such as BaS (JCPDS Card 01-0757), BaS 2 (JCPDS Card 21-0087), and BaS3 (JCPDS Card 03-0824).
AB - In this paper, we report the synthesis, structure and electrical properties of the perovskite-type AZn0.33+xNb0.67-xO 3-δ (A = Sr or Ba; 0 ≤ x ≤ 0.08). The investigated compounds were prepared by employing the solid-state (ceramic) reaction using alkaline nitrates, zinc oxide, and niobium oxide at elevated temperatures in air. Powder X-ray diffraction (PXRD) showed the formation of disordered Zn and Nb at the B-sites of space group Pm3̄m with cubic structure and a lattice constant comparable to that of the literature. The AC impedance study showed mainly bulk contribution to the total electrical conductivity over the investigated frequency range of 0.01 Hz to 1 MHz in all the investigated atmospheres even at low temperatures, which is significantly different from that of the well-known perovskite-type B-site ordered BaCa0.33+xNb 0.67-xO3-δ and the disordered acceptor-doped BaCeO3. The bulk dielectric constant determined at 500 and 700 °C in air was found to be in the range of 35-100. In air, the isothermal bulk dielectric constant seems to increase with an increasing Zn content, and a similar trend was observed for total electrical conductivity. In dry and wet H2, the electrical conductivity decreases with an increasing Zn content in AZn0.33+xNb0.67-xO3-δ, and the x = 0 member of the Ba compound exhibits the highest total conductivity of 7.2 - 10-3 S cm-1 in dry H2 at 800 °C. Both Sr and Ba compounds were found to be stable against the reaction with pure CO 2 at 700 °C and H2O at 100 °C for a long period of time. SrZn0.33+xNb0.67-xO3-δ was found to be stable in 30 ppm H2S at 800 °C, while the corresponding Ba compound formed reaction products such as BaS (JCPDS Card 01-0757), BaS 2 (JCPDS Card 21-0087), and BaS3 (JCPDS Card 03-0824).
U2 - 10.1021/ic101846f
DO - 10.1021/ic101846f
M3 - Article
AN - SCOPUS:78651312861
SN - 0020-1669
VL - 50
SP - 647
EP - 655
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 2
ER -