| A great number of experiments have been devoted to the investigation of normal-state anomalous behavior of high-temperature superconductors (HTSC). In the underdoped range, a well-defined feature is the opening of a pseudogap at a characteristic temperature, T* (T* > TC). For optimal doping, T* is nearly equal to or lower than TC. Meanwhile, there is another anomalous behavior around 220 K for optimally doped YBa2Cu3O7-δ (Y123). Such anomalous behavior has been indicated by the temperature dependent mechanical energy dissipation spectra, where a broad peak was observed (labeled as P3). And this peak has been extensively studied among different frequency ranges. Many other experiments also indicate the existence of an anomalous behavior around there, such as the helium-ion channeling experiment, specific heat, high-resolution thermal expansion, nuclear quadrupole resonance, Raman spectroscopy, and Hall number density. To obtain a clear understanding of the origin of P3, we performed the internal friction study of Zn,Ni and Fe doped Y123. We also studied the internal friction of Y123 in the different carrier doping range. Our new results of internal friction spectra of overdoped Y123 show the close relationship of P3 with the normal-state anomalous behavior of HTSC. Our further internal friction study of Sr substituted Y123 provides more information about P3 internal friction peak. We present an approach relating this peak to the crossover in charge-carrier dynamics.The pressure dependence of the transition temperature TC of copper oxide high-temperature superconductors is of fundamental interest for elucidating the microscopic mechanism of the superconductivity. It is generally believed that one of the key parameters controlling the TC values is the charge carrier concentration in the CuO2 planes, and it is postulated that the application of high pressure leads to the change of carrier concentration resulting in the pressure dependence of TC. However,...
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