Topochemical manipulation of perovskites: low-temperature reaction strategies for directing structure and properties

Topochemical reaction strategies offer an important low-temperature (<500 °C) approach to the conscious manipulation of various inorganic host materials, allowing access to compounds that cannot be prepared by standard high-temperature methods. As the utility of these strategies continues to expand, researchers will be able to more effectively target materials with technologically significant properties. This Progress Report presents recent advances in topochemical reaction strategies as applied to perovskite and perovskite-related compounds. Emphasis is placed on structural modifications and corresponding variations in properties. Additionally, the future prospects of this approach to the rational design of intricate target compounds are discussed.

Evidence of Two-Dimensional Superconductivity in the Single Crystalline Nanohybrid of Organic-Bismuth Cuprate

A coordination compound of HgI(2)(pyridine)(2) can be successfully intercalated into a single crystalline Bi(2)Sr(2)CaCu(2)O(y) high-T(c) superconductor through an interlayer complexation reaction between pyridine molecules and bismuth cuprate pre-intercalated with mercuric iodide. X-ray diffraction and X-ray absorption spectroscopic results clearly demonstrate that the single crystalline nature of the pristine bismuth cuprate remains unchanged even after the intercalation of organic complex as well as those of iodine and mercuric iodide. According to the angle-dependent dc magnetization measurements, the intercalation of bulky organic molecules completely blocks superconductive currents along the c-axis, whereas a superconducting transition along the in-plane direction still occurs in the organic intercalate. In the case of the iodine or mercuric iodide intercalates with smaller lattice expansions, an out-of-plane diamagnetic transition is not wholly quenched but significantly depressed by the intercalation, confirming the reduction of interlayer interaction. The present finding can provide straightforward evidence of the two-dimensionality of high temperature superconductivity in the present cuprate-based nanohybrid material.

A Novel Hybrid of Bi-Based High-Tc Superconductor and Molecular Complex

Molecular complex HgI2Py2 (Py=pyridine) was intercalated into the Bi-based high-Tc cuprate by intercalative complexation. The intercalation method adopted in this work is based on the new concept, where a neutral ligating agent is diffused into the preintercalated HgI2 layer leading to a charge transfer-type complex formation between the Bi2O2 double layers of Bi2Sr2CaCu2Oy.