Anomalous perovskite PbRuO3 stabilized under high pressure

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• Perovskite oxides (ABO3) are crucial electronic materials with a characteristic crystal structure.
• The corner-shared BO6 octahedra framework in perovskites typically hinders strong A-B cation bonding.
• Previous research has not reported strong A-B cation bonds in perovskite structures.

Purpose of the Study:

• To investigate the structural and electronic behavior of lead ruthenium oxide (PbRuO3) under high pressure.
• To identify and characterize any pressure-induced phase transitions in PbRuO3.
• To explore the formation of unusual cation-cation bonding under extreme conditions.

Main Methods:

• Synchrotron X-ray diffraction was used to analyze structural changes at high pressures.
• Resistivity measurements and Raman spectroscopy provided complementary data on the phase transition.
• First-principles calculations were employed to simulate the material's behavior and validate experimental findings.

Main Results:

• A pressure-induced first-order phase transition in PbRuO3 from the Pbnm to the polar Pbn21 orthorhombic phase was observed at 32 GPa.
• The Pbn21 phase exhibits highly distorted octahedra and the shortest Pb-Ru bond length ever reported in a perovskite.
• Calculations accurately predicted the transition pressure and lattice parameter evolution, revealing increased Ru:t2g and Pb sp orbital hybridization.

Conclusions:

• High pressure can induce a transition to a polar perovskite phase in PbRuO3, challenging the notion of weak A-B cation bonding.
• The observed shortest Pb-Ru bond is attributed to pressure-enhanced orbital hybridization, leading to bonding and antibonding states.
• This study demonstrates the potential for creating novel materials with unique electronic properties through pressure engineering of perovskites.