Time-Dependent Degradation Due to the Gradual Phase Change in BICUVOX and BICOVOX Oxide-Ion Conductors at Temperatures below about 500°C
Time-Dependent Degradation Due to the Gradual Phase Change in BICUVOX and BICOVOX Oxide-Ion Conductors at Temperatures below about 500°C
复制标题
由于 BICUVOX 和 BICOVOX 氧化物离子导体在温度低于 500°C 时逐渐发生相变，导致随时间的退化
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发表时间：
2002
期刊：
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通讯作者：
Kalpataru Das
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作者：
A. Watanabe;Kalpataru Das
摘要 本文描述了在代表性 BIMEVOX 相 Bi2Cu0.1V0.9O5.35 (BICUVOX.10) 和 Bi2Co0.1V0.9O5.35 (BICOVOX.10) 中观察到的电导率随时间下降的原因。迄今为止，在这两个相中，均报道了以下事实：高温稳定的γ型相在450-500℃下通过有序-无序转变可逆地转变为低温稳定的γ'型相，而没有转变为β型或α型相。此外，在 420°C 左右，γ'-BICUVOX.10 中观察到电导率下降。在本研究中，结果表明，在 450°C 下持续退火数百小时会导致两个 γ' 相转变成具有 α-Bi4V2O11 相关结构的新相。这种 α 相关相在加热时迅速转变为 γ 相（BICOVOX.10 约为 535°C，BICUVOX.10 约为 485°C）；相比之下，γ′相缓慢地回复到α相关相。由于 α 相关相显示出低得多的电导率（BICUVOX.10 在 430°C 时为 10−4.8S cm−1），这种逐渐的 γ' 到 α 转变很好地解释了迄今为止报道的 γ' 相电导率随时间变化的情况。即，在低于α-γ转变温度的热处理时，γ'相亚稳态淬火至室温并逐渐恢复为α相关相。
Abstract This paper describes a cause of the time-dependent degradation of conductivity observed in the representative BIMEVOX phases Bi2Cu0.1V0.9O5.35 (BICUVOX.10) and Bi2Co0.1V0.9O5.35 (BICOVOX.10). In both phases, to date, the following facts were reported: the high-temperature stable γ-type phase transformed reversibly to the low-temperature stable γ′-type phase at 450–500°C through the order–disorder transition without changing to the β-type or α-type phase. In addition, the degradation of conductivity was observed in γ′-BICUVOX.10 at about 420°C. In the present study, it has turned out that a prolonged annealing at 450°C for several hundred hours causes both γ′ phases to change to a new phase with α-Bi4V2O11-related structure. This α-related phase changes promptly to the γ phase on heating (at about 535°C for BICOVOX.10 and at about 485°C for BICUVOX.10); by contrast, the γ′ phase reverts sluggishly to the α-related phase. Since the α-related phase shows far lower conductivity (10−4.8S cm−1 at 430°C for BICUVOX.10), this gradual γ′-to-α transition explains well the time-dependent degradation of conductivity in the γ′ phase reported so far. Namely, the γ′ phase is metastably quenched to room temperature and reverts gradually to the α-related phase upon heat treatment below the α-to-γ transition temperature.