Four decades of research in solid state chemistry

Abstract

at the University of Cambridge. He is the author of over 800 research papers and has authored/edited 30 books pertaining to solid state chemistry, spectroscopy, molecular structure, surface science and chemical education. He is a member of the editorial boards of over 15 international journals and is the founder-editor of the Bulletin of Materials Science. He is Honorary 405

Electronic phase separation in the rare-earth manganates (La1−xLnx)0.7Ca0.3MnO3 (Ln = Nd, Gd and Y)

“…We have examined the electrical and magnetic properties for a series of (La 1-x Electrical conductivity in the x ≈ x c compositions, are percolative at low temperatures and accordingly, we are able to fit the low temperature data for the compositions with < r A > > 1.18 Å to a percolative scaling law, logρ ∝ log| < r A >-< r A c >| as shown in Fig.9. The slope of the plot is -2.63, a value close to the experimental and predicted values for percolative systems [3].…”

“…Compositions of the formula (La 1-x Ln x ) 0.7 Ca 0.3 MnO 3 (Ln = Nd, Gd or Y) were prepared by standard solid-state synthesis. A stoichiometric mixture of the rare earth acetate, CaCO 3 and MnO 2 were mixed thoroughly in an agate mortar with the help of iso-propyl alcohol, and the mixture was first fired to 1273 K for 48 h with two intermediate grindings. This preheated sample was then further heated at 1473 K for 24 h, pressed into pellets and fired to 1648 K for 12 h to obtain the single-phase compounds.…”

“…Rare earth manganates of the general formula Ln 1-x A x MnO 3 (Ln = rare earth, A = alkaline earth) exhibit many interesting properties such as colossal magnetoresistance, charge ordering and electronic phase separation [1][2][3]. Phase separation in these materials has attracted much interest in the last few years because of the fascinating features associated with the phenomenon [3]. Of the various manganite compositions, the (La 1-x Pr x ) 0.7 Ca 0.3 MnO 3 system has provided really valuable information on the electronic phase separation [4][5][6].…”

Novel Materials through Non-Hydrolytic Sol-Gel Processing: Negative Thermal Expansion Oxides and Beyond

“…Careful modification of stoichiometry and doping, formation of desired particle size and morphology, and control of crystal structure are crucial targets in many cases. A variety of soft chemistry or “chimie douce” routes have been developed, which give access to stable and metastable polymorphs [1,2,3,4,5,6,7,8,9,10,11,12]. Methods include chemical vapor deposition [13], ion exchange [14], intercalation [15], flux synthesis [12,16], topotactic transformations of precursors [12,17], hydrothermal synthesis [12,18,19], and sol-gel reactions [8,12,20,21].…”