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Download fileBa33Zn22Al8O67 with a Framework of ([O(Zn/Al)4]/Ba)(Zn/AlO4)4 Motifs
journal contribution
posted on 2021-10-27, 14:48 authored by Rayko Simura, Kyosuke Sawamura, Hisanori Yamane, Takuji IkedaSingle crystals of
a new oxide, Ba33Zn22Al8O67 (melting point = 1452 K), were grown in a melt-solidified
sample prepared by heating a compact of a BaCO3, ZnO, and
Al2O3 mixed powder in a dry airflow. Ba33Zn22Al8O67 can be handled
in dry air, but it decomposes into carbonates, hydroxides, and hydrates
in humid air. Single-crystal X-ray structure analysis clarified that
Ba33Zn22Al8O67 crystallizes
in a cubic cell (a = 16.3328 (3) Å, space group F23) having a three-dimensional Zn/AlO4 framework
in which {([OZn4]/Ba)(Zn/AlO4)4}
motifs are connected to each other by bridging Zn/AlO4 tetrahedra.
A Ba atom or a [OZn4] cluster is statistically situated
at the center of the motif with a probability of 0.5. Motifs of another
type, {([O(Zn/Al)4])(Zn/AlO4)4},
are isolated from the Zn/AlO4 framework. These motifs,
{([OZn4]/Ba)(Zn/AlO4)4} and {([O(Zn/Al)4])(Zn/AlO4)4}, are alternatingly arranged
along the a axis like a checkered cube, and Ba atoms
are situated between the motifs. A linear thermal expansion coefficient
of 10.4 × 10–6 K–1 was measured
in an Ar gas flow at 301–873 K for a sintered Ba33Zn22Al8O67 polycrystalline sample
with a relative density of 73%. A relative permittivity of 31 and
a temperature coefficient of 15 ppm K–1 at 301 K
were obtained for another sintered sample (relative density = 70%)
in a dry airflow. The electrical conductivity at 1073 K and the activation
energy for conduction at 923–1073 K measured for the sintered
samples in dry and wet airflows were 6.2 × 10–7 S cm–1 and 0.65 eV and 2.9 × 10–6 S cm–1 and 0.59 eV, respectively.
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cubic cell (<ar gas flowalternatingly arranged alongsolidified sample prepared9 × 104 × 108 </ sub67 </ sub4 </ sub33 </ sub22 </ sub15 ppm k1452 k ),2 × 10al )< sub2 </ subanother sintered sample3 </ submotifs single crystalspolycrystalline samplef </another typesintered samples301 k1073 ksintered bawet airflowstemperature coefficientspace grouprelative permittivityrelative densitynew oxidemixed powdermelting pointhumid airelectrical conductivitycrystal xcheckered cubeaxis likeactivation energy73 %.70 %)65 ev59 ev