Crystal chemistry, thermal expansion and dielectric properties of (Bi1.5Zn0.5)(Sb1.5Zn0.5)O7 pyrochlore

Electrical properties of Bi1.5ZnSb1.5O7 pyrochlore ceramics

“…Mergen and Lee [7] determined that Bi 1.5 ZnSb 1.5 O 7 has a dielectric constant of around 32 with a dielectric loss of about 0.005 at 20 °C and weakly temperature dependent between 20 and 120 °C [7]. The dielectric permittivity measured by impedance spectroscope in the frequency range from 5 Hz to 13 MHz between 100 and 500 °C gave values in the range 40-48 exhibiting slight dependence of dielectric losses with temperature up to 400 °C [8].…”

Structural Study of an Unusual Cubic Pyrochlore Bi1.5Zn0.92Nb1.5O6.92

“…Based on the nominal composition and the indexed X-ray powder diffraction patterns, the Bi 1.5 ZnNb 1.5 O 7 compound was claimed to exhibit a cubic pyrochlore structure A 2 B 2 O 7 , implying that the Zn ions occupy both A-and B-sites (5). However, in the absence of detailed structural/compositional data, the presence of rather small Zn ions (6) on the eight-fold coordinated A-sites remained controversial (7,8), because the ionic radius of Zn falls outside the known limits of structural stability for pyrochlores (9). The other compound, Bi 2 Zn 2/3 Nb 4/3 O 7 , was reported to crystallize with a distorted pyrochlore structure (6); however, it was recently confirmed that this compound adopts a monoclinic zirconolitelike arrangement (space group C2/c, a=13.1037(9) ( A, b=7.6735(3) ( A, c=12.1584(6) ( A, b=101.318(5)) (10).…”

The Electrical and Defect Properties of Bi3Zn2Sb3O14Pyrochlore: A Grain-Boundary Phase in ZnO-Based Varistors

“…These additives interact in complex ways to serve various functions: Bi 2 O 3 melts during processing, thus allowing liquid-phase sintering [2,3]; Co leads to development of interface states [3] that insure the development of sufficiently high space-charge barriers at the grain boundaries. The presence of Sb derived from the addition of Sb 2 O 3 controls microstructure through formation of a secondary spinel phase, Zn 7 Sb 2 O 12 , that impedes grain growth [2][3][4]. However, these oxide additions also result in the formation of another secondary phase at grain boundaries: a pyrochlore shown to have composition Bi 3 Zn 2 Sb 3 O 14 .…”