Abstract Undoped LnVO 4 and magnesium-doped Ln 0.95 V 0.95 Mg 0.10 O 4-δ (Ln = Pr, Sm, Gd, Dy and Er) orthovanadates were synthesized by solid state reaction method and characterized by XRD, SEM/EDS, electrical conductivity measurements in controlled atmospheres, and modified e.m.f. technique for determination of oxygen-ion transference numbers. XRD analysis showed the formation of phase-pure materials with tetragonal zircon-type structure and a decrease in lattice parameters with a decrease of ionic radius of rare-earth cations. Trace amounts of MgO and Mg-V-O phases revealed by SEM/EDS suggest that the solid solubility limit of magnesium cations in LnVO 4 lattice is somewhat lower than the nominal doping level, and that magnesium substitutes preferentially into the vanadium sublattice. LnVO 4 and Ln 0.95 V 0.95 Mg 0.10 O 4-δ orthovanadates show semiconducting behavior under oxidizing conditions at 450–950 °C and are predominantly oxygen-ionic conductors, except PrVO 4 that shows mixed conductivity. In the LnVO 4 series, electrical conductivity is the highest for PrVO 4 and SmVO 4 (~4 × 10 −4 S/cm at 800 °C) and decreases with increasing atomic number of rare-earth cation for the other compositions. Additions of magnesium results in a drop of electrical conductivity, by 1.5–2 times for most of compositions. Interstitial oxygen diffusion is discussed as a prevailing mechanism of ionic transport in undoped LnVO 4 , whilst acceptor-type magnesium doping suppresses the formation of interstitial oxygen ions. Humidity has a rather negligible impact on the electrical properties of substituted ceramics, indicating only minor (if any) protonic contribution to the total electrical transport of the studied orthovanadates.

中文翻译：

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镁掺杂锆石型稀土原钒酸盐：结构和电学表征

摘要 采用固态反应法合成了未掺杂的 LnVO 4 和掺杂镁的 Ln 0.95 V 0.95 Mg 0.10 O 4-δ (Ln = Pr、Sm、Gd、Dy 和 Er)原钒酸盐，并通过 XRD、SEM/EDS、电导率表征。受控气氛中的测量，以及用于测定氧离子迁移数的改良电动势技术。XRD分析表明形成了具有四方锆石型结构的相纯材料，并且随着稀土阳离子的离子半径的减小，晶格参数减小。SEM/EDS 显示的痕量 MgO 和 Mg-VO 相表明，LnVO 4 晶格中镁阳离子的固溶度极限略低于标称掺杂水平，并且镁优先替代到钒亚晶格中。LnVO 4 和 Ln 0.95 V 0.95 Mg 0。10 O 4-δ 原钒酸盐在 450–950 °C 的氧化条件下显示出半导体行为，并且主要是氧离子导体，除了 PrVO 4 显示混合导电性。在LnVO 4 系列中，PrVO 4 和SmVO 4 的电导率最高（800°C 时~4 × 10 -4 S/cm），并随着其他组合物的稀土阳离子原子序数的增加而降低。添加镁会导致电导率下降，大多数组合物的电导率下降 1.5-2 倍。间隙氧扩散被讨论为未掺杂的 LnVO 4 中离子传输的主要机制，而受体型镁掺杂抑制间隙氧离子的形成。湿度对替代陶瓷的电性能的影响可以忽略不计，