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Anelastic relaxation from hydrogen and other defects in La-doped BaTiO_3

机译：La掺杂BaTiO_3中氢和其他缺陷的弹性松弛

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摘要

We present anelastic spectroscopy measurements between 2 and 500K in Ba_(1-x)La_xTiO_3 (0.10 ≤x ≤ 0.20). The phase transitions of pure BaTiO_3 are shifted to lower temperature by increasing the La doping and are completely suppressed starting from x = 0.15. The samples are expected to contain H impurities since sintering was performed in flowing H_2 to ensure electronic rather than cation vacancy compensation, and indeed at least three relaxation processes of the complex anelastic spectrum are strongly influenced by annealing the samples in CO or H_2 at 1450 K. A thermally activated anelastic peak around 250 K (f ～ 2 kHz) is ascribable to H hopping between different O atoms, while a possible indication of fast reorientation around a same O atom comes from a broad peak around 100 K. At least other three relaxation processes are present between 30 and 150 K, but the present data do not allow their nature to be ascertained; possible mechanisms involve polarons and hopping of Ti and possibly La among off-centre positions.
机译：我们目前在Ba_（1-x）La_xTiO_3（0.10≤x≤0.20）中的2到500K之间进行非弹性光谱测量。通过增加La掺杂，纯BaTiO_3的相变转移到较低的温度，并且从x = 0.15开始被完全抑制。由于在流动的H_2中进行烧结以确保电子而不是阳离子空位补偿，因此预计样品中将包含H杂质，并且通过在1450 K下在CO或H_2中对样品进行退火，实际上至少对复合无弹性谱的至少三个弛豫过程有很大影响。大约250 K（f〜2 kHz）处的热活化无弹性峰是由于不同O原子之间的H跃迁引起的，而在同一O原子周围快速重新取向的可能迹象来自于100 K附近的宽峰。弛豫过程存在于30 K和150 K之间，但是目前的数据无法确定其性质；可能的机制包括极化子以及偏心位置中Ti以及La的跃变。

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