Rational Molecular Engineering of Ceramic Materials

Abstract

Most of the advances in modern ceramics have been based on the development of a new material.A rational approach to the design and execution of such innovative syntheses can be made more scientific and less serendipitous. The understanding of molecular architecture and the principles of structure building can only be based on the science of crystal chemistry and solidstate thermodynamics. This review presents a summary of the principles and state-of-the-art empirical data in relevant crystal chemistry and the correlates found in phaseequilibrium diagrams. It dealsexplicitly with the role of metastable equilibrium in the formation and use of technological materials. It also summarizes the major classes of experimental facilities needed for sophisticated molecular engineering. Several examples are presented as successful paradigms of rational molecular engineerin covering different size ranges of creative architecture proposed as being based principally on 2-(or multi-) phase materials, andor on noncrystalline phases based on the entire composition range of ceramics, and on combinations of ceramics with metals and, possibly, polymers.from 10 f to 10 pm. Likely future developments in this areaare

Analysis and Structural Determination of Nd-Substituted Zirconolite-4M

“…In the multiphase titanate wasteform known as Synroc (1), the lanthanides are immobilized in solid solution within the zirconolite phase CaZr V Ti \V O and in the perovskite phase CaTiO (2). The principal reasons for including zirconolite in Synroc is that it occurs naturally with significant proportions of crystallochemically bound uranium and thorium (3) and is known to have withstood the long term effects of high level doses of alpha radiation without significant degradation (4). In the present paper we have investigated how zirconolite accommodates neodymium Nd>, one of the largest of the trivalent elements in the lanthanide group, at concentrations between 0.5 and 0.8 Nd per formula unit.…”

Group IVB oxide enhancement of the iron‐enriched basalt waste form

“…Aluminosilicate glass is highly regarded as a candidate waste form; however, in view of the very long half-lives of many actinides, incorporation of these isotopes into a durable crystalline phase would have been preferred. This view is borne out by Roy [8]: "The glass... does not meet the constraint of thermodynamic stability since it is metastable by definition. .. .the solubility of the glass in the same solvent must be greater than the total solubility of the stable crystalline assemblage."…”

Ferroelectric ceramics I. – Theoretical background, materials and properties

“…Ez az új iparág "hagyományos" nyersanyagokkal szigetelő kerámiák, oxidok, kerámia dielektrikumok, kondenzátoranyagok gyártásával indult el. A termékválaszték később kerámiai félvezetőkkel, mágneses kerámiákkal, piezoelektromos anyagokkal és új, molekuláris szinten tudatosan tervezett anyagrendszerekkel bővült [3].…”