Glimpses of 60 years of research in materials chemistry
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troduction It has been nearly 60 years since I thought of the chemistry of solid materials as an area that provided great scope for research, because the subject was in its infancy.1,2 It was also an area where I could make some contribution from India, where laboratory facilities were meager. There was little support at that time to buy instruments or set up a well-equipped laboratory. There were no spectrometers or x-ray diffractometers. Having returned from the US after several years of productive stay, it was a testing time for me to initiate a meaningful research program in the late 1950s in India. Instead of spectroscopy and molecular structure being the main focus of my research, I started working on simple materials chemistry problems. Some aspects of electronic as well as vibrational spectroscopy were still pursued, using whatever facility was available in India, often depending on help from friends abroad.
The first problem that we addressed was the transformation of the anatase and brookite forms of TiO2 to the rutile form.3–5 We studied kinetics and other aspects of the transformations using a tiny powder diffraction camera. Phase transformation of alkali halides was next, including an experimental study of the transformation of CsCl and its solid solutions with KCl.6 The Born model was used to explain the stability of phases. We also started to carry out calculations on point defects in ionic solids. My interest in phase transitions in solids continued, and I eventually wrote a book7 on the subject with K.J. Rao. From 1950 to 1970, one of the main preoccupations of chemists working on solids was understanding nonstoichiometry. The problem was explaining the structures and stabilities of materials such as Ti4O7, Pr6O11, and Fe7S8 (in contrast to NaCl or ZnO). I wanted to study praseodymium and terbium
C.N.R. Rao, Jawaharlal Nehru Centre for Advanced Scientific Research, India; [email protected] doi:10.1557/mrs.2018.35
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Glimpses of 60 years of research in materials chemistry Transition-metal oxides When research on transition-metal oxide systems began in the 1960s, many metallic oxides were discovered (Figure 1a).11–13 For example, ReO3 had the appearance of and conducted like copper. Oxides exhibiting metal–insulator (M–I) transitions (Ti2O3, VO2, V2O3) were soon discovered (Figure 1b). V2O3 undergoes a transition with a 10-million-fold jump in resistivity at 150 K, when there is also a transition to the antiferromagnetic state. Work was conducted on metallic oxides as well as oxides showing M–I transitions.11,12 Around 1965, work on properties and pheFigure 1. (a) Electrical resistivities of highly conducting (metallic) oxides. (b) The well-known nomena exhibite
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