Abstract

The vanadate Na₃ErV₂O₈ with a glaserite type structure was obtained by solid-phase synthesis in air. The unit cell parameters (space group P2₁/n) calculated from powder X-ray diffraction data at room temperature were a = 5.488 Å, b = 9.723 Å, c = 7.213 Å, β = 93.06°. The phase transition from the low-temperature α-phase to the high-temperature β-phase at 866°С has an enthalpy of 36.9 J/g. According to dilatometric measurements, the linear thermal expansion coefficient (α_L) increases from 8.0 × 10^–6 to 12.5 × 10^–6 K^–1 in the α-phase. The α → β phase transition is accompanied by sharp expansion of Na₃ErV₂O₈ and increase in α_L to 15.0 × 10^–6 K^–1 in the β-phase. The electrical conductivity (σ) was studied by impedance spectroscopy as a function of temperature and partial oxygen pressure (\({{p}_{{{{{\text{O}}}_{{\text{2}}}}}}}\)) in the gas phase. The invariability of σ values over a broad \({{p}_{{{{{\text{O}}}_{{\text{2}}}}}}}\) range attests to the ionic character of electrical conductivity. According to the Tubandt method, the charge carriers are sodium cations.

中文翻译：

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芒硝型结构钒酸盐 Na3ErV2O8 中的钠离子迁移和相变

摘要

通过在空气中固相合成获得了具有芒硝型结构的钒酸盐Na ₃ ErV ₂ O _{8 。}从室温下的粉末 X 射线衍射数据计算的晶胞参数（空间群P 2 ₁ / n ）为a = 5.488 Å，b = 9.723 Å，c = 7.213 Å，β = 93.06°。在 866°С 时从低温 α 相到高温 β 相的相变具有 36.9 J/g 的焓。根据膨胀测量，线性热膨胀系数 (α _L ) 从 8.0 × 10 ^–6增加到 12.5 × 10 ^–6 K ^–1在α相。α→β相变伴随着Na ₃ ErV ₂ O ₈的急剧膨胀和β相中α _L增加到15.0 × 10 ^-6 K ^-1。电导率 (σ) 通过阻抗谱研究作为温度和氧分压的函数 ( \({{p}_{{{{{\text{O}}}_{{\text{2}}} }}}}\)）在气相中。σ 值在广泛的\({{p}_{{{{{\text{O}}}_{{\text{2}}}}}}}\)范围内的不变性证明了导电性。根据 Tubandt 方法，电荷载流子是钠阳离子。