Ultrasonic determination of the elastic properties and their pressure and temperature dependences in very dense YBa2Cu3O7-x.
Ultrasonic determination of the elastic properties and their pressure and temperature dependences in very dense YBa2Cu3O7-x.
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DOI：
10.1103/physrevb.46.1157
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发表时间：
1992-07
期刊：
影响因子：
--
通讯作者：
M. Cankurtaran;G. A. Saunders;K. Goretta;R. B. Poeppel
中科院分区：
文献类型：
--
作者：
M. Cankurtaran;G. A. Saunders;K. Goretta;R. B. Poeppel
测量了静水压力和温度对${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{x}}$.陶瓷样品中纵波和横波传播速度的影响。在密度如此高的${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{x}}$陶瓷中，气孔率对弹性性能的影响应该大大减小。然而，这种致密材料的体积弹性系数与密度小得多的${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{x}}$陶瓷的超声测量结果一样小(=55 Gpa)。在10-300K温度范围内测量的纵波和横波的速度随温度的变化关系表明，冷却时在约200K处呈阶梯状增加，在升温过程中在约225K处出现类似的下降，滞后范围在190-235K之间，这一特征以前在密度较低的陶瓷中观察到，并初步归因于相变。
The effects of hydrostatic pressure and temperature have been measured on the velocities of longitudinal and shear ultrasonic waves propagated in a very dense (96% of theoretical density) ceramic specimen of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{x}}$. In ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{x}}$ ceramics with such a high density, the effects of porosity on the elastic properties should be much reduced. Nevertheless the bulk modulus of this dense material has the same small magnitude (=55 GPa) as that measured ultrasonically in much less dense ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{x}}$ ceramics. The temperature dependences of the velocities of longitudinal and shear ultrasonic waves, which have been measured between 10 and 300 K, show a steplike increase at about 200 K on cooling and a similar decrease at about 225 K during warming with hysteresis in the range 190--235 K, features previously observed in less dense ceramics and tentatively attributed to a phase transformation.