High-Temperature Ultrasound Attenuation in Langasite and Langatate
High-Temperature Ultrasound Attenuation in Langasite and Langatate
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DOI：
10.1109/tuffc.2018.2836434
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发表时间：
2018-05
期刊：
影响因子：
--
通讯作者：
C. Hirschle;J. Schreuer
中科院分区：
文献类型：
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作者：
C. Hirschle;J. Schreuer
随着温度的升高，在 800 K 左右，硅锰矿晶体中的超声衰减迅速增加，其原因尚不清楚。本文利用共振超声光谱研究了硅酸镁锰矿型材料 La3Ga5SiO14 (LGS) 和 La3Ta0.5Ga5.5O14 (LGT) 从室温到 1653 K 和 1608 K 的衰减量，量化为 $Q^{-1}$。可以看到两到三个衰减峰。 LGT 中最大两个衰减峰幅度的变化与 LGT 样品颜色的变化相关，而 LGT 样品的颜色变化又与其氧空位浓度相关。因此，衰减可能涉及氧空位。观察到的 $Q^{-1}$ 可以通过基于两到三个非相互作用点缺陷的滞弹性松弛的模型来很好地解释，该模型会导致德拜峰状衰减最大值。最大的两个弛豫峰的活化能与 LGS 和 LGT 中不同导电机制的活化能相匹配。因此，基于氧运动的电导率和弛豫过程似乎涉及相同位置上的离子和空位的交换。最大的两个衰减峰可能是由两种不同现象引起的离子运动引起的，一方面是晶格变形（点缺陷弛豫），另一方面是通过压电效应产生的电场（压电/载流子弛豫）。
The ultrasound attenuation in langasite crystals increases rapidly at about 800 K with increasing temperature for reasons that are not well understood. In this paper, the attenuation quantified as $Q^{-1}$ of the langasite-type materials La3Ga5SiO14 (LGS) and La3Ta0.5Ga5.5O14 (LGT) was studied from room temperature to 1653 and 1608 K, respectively, using resonant ultrasound spectroscopy. Two to three attenuation peaks can be seen. A change of the magnitudes of the largest two attenuation peaks in LGT was correlated with the changing color of an LGT sample, which is related to its oxygen vacancy concentration. Thus, the attenuation likely involves oxygen vacancies. The observed $Q^{-1}$ can be explained well by a model based on the anelastic relaxation of two to three noninteracting point defects causing Debye peak-like attenuation maxima. The activation energies of the largest two relaxation peaks match the activation energies for different conductivity mechanisms in LGS and LGT. Thus, the oxygen movement-based conductivity and the relaxation processes seem to involve the exchange of ions and vacancies on the same positions. The largest two attenuation peaks are probably caused by the movement of ions induced by two different phenomena, the deformation of the lattice (point-defect relaxation) on the one hand and the electric field via the piezoelectric effect (piezoelectric/carrier relaxation) on the other hand.