Abstract
The effects of pressure in electronic and vibrational properties of the double perovskite CaCu3Ti4O12 have been investigated in the 0-25 GPa range by optical absorption and Raman spectroscopy. Besides a full structural characterization, we aim at unveiling whether the ambient crystal structure is stable under high pressure conditions and how its giant dielectric permitivity and electronic gap varies with pressure. Results show that there is evidence of neither structural phase transition nor metallization in CaCu3Ti4O12 in the explored pressure range. We have observed the eight Raman active modes associated with its crystal phase and obtained their corresponding frequency and pressure shift. Moreover, the direct electronic band gap (2.20 eV), which is mainly associated with the oxygen-to-copper charge transfer states, increases slightly with pressure at a rate of 13 meV GPa−1 from 0 to 10 GPa. Above this pressure is almost constant (Eg = 2.3 eV). The results highlight the high stability of the compound in its phase against compression.
Highlights
CaCu3Ti4O12 (CCTO) is a double perovskite oxide which acquired interest due to its giant dielectric permittivity (16000-18000) at ambient conditions [1, 2, 3]
The effects of pressure in electronic and vibrational properties of the double perovskite CaCu3Ti4O12 have been investigated in the 0-25 GPa range by optical absorption and Raman spectroscopy
Experiments on thin films of CCTO showed a low frequency permittivity of about 108 [7], that supports the hypothesis of extrinsic defects as the main cause for the giant dielectric constant
Summary
CaCu3Ti4O12 (CCTO) is a double perovskite oxide which acquired interest due to its giant dielectric permittivity (16000-18000) at ambient conditions [1, 2, 3]. The effects of pressure in electronic and vibrational properties of the double perovskite CaCu3Ti4O12 have been investigated in the 0-25 GPa range by optical absorption and Raman spectroscopy. Results show that there is evidence of neither structural phase transition nor metallization in CaCu3Ti4O12 in the explored pressure range.
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