The high-pressure synthesis and in situ property of the infinite-layer CaCuO2

The infinite-layer CaCuO2 (IL CaCuO2) was synthesized at ∼1000 deg. C and 3 GPa, and structural and electrical properties under high-pressure were studied at room temperature using a diamond anvil cell (DAC) by in situ high-pressure energy-dispersive X-ray diffraction with synchrotron radiation and by electrical measurements, respectively. The results reveal that the primary crystal structure of IL CaCuO2 is stable under pressure up to 30 GPa. The equation of state of IL CaCuO2 was obtained from the V/V 0-P relationship, which gives rise to a bulk modulus B 0 = 181 GPa for IL CaCuO2 based on the Birch-Murnaghan equation. The resistance and capacitance measurements of IL CaCuO2 up to 20 GPa indicate that there is an abnormal hump occurring around 10 GPa with increasing pressure. Corresponding changes were also observed in the dependence of capacitance on pressure. It is considered to be related to an electronic structure transition resulting from the anisotropic compression of the IL CaCuO2 unit cell under high pressure, which can be attributed to the sudden disappearance of an X-ray diffraction peak