Questions? Call 800-624-6242 About | Ordering | New Menu | Items in cart [0] SEARCH

PAPERBACK price:$43.25 add to cart Rights & Permissions Free PDF Access Sign in to download PDF book and chapters Free Resources PDF SUMMARY Display this book on your site! Related Titles Condensed-Matter Physics Advancing Materials Research Other Related Titles Frontiers in Crystalline Matter: From Discovery to Technology (2009) Board on Physics and Astronomy (BPA) Citation Manager Export the bibliographic data for this book in your chosen format Web Search Builder Use this book's key terms to search within this book, across our collection, or across the Web. Skim This Chapter Skim this chapter and use this chapter's key terms to search within this book. Reference Finder Paste in your own text to find books that relate to your topic. Citation Manager . "Appendix E: Classes of Materials." Frontiers in Crystalline Matter: From Discovery to Technology. Washington, DC: The National Academies Press, 2009. Please select a format: Page 169   E-mail Share on facebook Facebook Share on delicious Delicious Share on stumbleupon Stumble Share on twitter Twitter More Sharing ServicesMore The following HTML text is provided to enhance online readability. Many aspects of typography translate only awkwardly to HTML. Please use the page image as the authoritative form to ensure accuracy. Appendix E Classes of Materials ORGANICS Also called molecular crystals, organics are composed of carbon-based molecules. This group of materials also includes inorganic coordination compounds, which are sometimes referred to as metallo-organic or organometallic compounds. Organics exhibit many technologically important properties, such as magnetic ordering, high electrical conductivity, high- and low-dielectric constants, piezoelectricity, and superconductivity. Like atoms in inorganic materials, dissimilar molecules can be co-crystallized. Although generally thought of as being neutral species, when the electronegativities of co-crystallized molecules are sufficiently different, electron transfer occurs creating anions and cations, and examples can exhibit high direct current electrical conductivity or ferromagnetic ordering. When intermediate differences in the electronegativities occur, charge-transfer complexes form. OXIDES Oxides are materials containing oxygen as a primary anion—examples of current interest are BaTiO3 (a ferroelectric), YBa2Cu3O7 (a superconductor), and La1-xSrxMnO3 (a magnetoresistive material). The wide range of behavior found in metal oxides is due in part to the presence of strong interactions between metal d electrons and oxygen p electrons and a delicate balance between nearly energetically equivalent electronic configurations that involve coupling between electronic, Page 169 Front Matter (R1-R16) Summary (1-6) 1 Introduction (7-32) 2 Science and Technology of Crystalline Systems (33-94) 3 The Status of Activities in the Discovery and Growth of Crystalline Materials (95-125) 4 Conclusions and Recommendations (126-142) Appendixes (143-144) Appendix A: Charge to the Committee (145-145) Appendix B: Biographies of Committee Members (146-152) Appendix C: Meeting Agendas (153-156) Appendix D: Synthesis Techniques (157-168) Appendix E: Classes of Materials (169-170) Appendix F: Working Draft of Policies and Procedures for a Crystalline Materials Network (171-173) Appendix G: Educational Role of Centers of Expertise for Discovery and Growth of Crystalline Materials (174-176)

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 169
Frontiers in Crystalline Matter: From Discovery to Technology Appendix E Classes of Materials ORGANICS Also called molecular crystals, organics are composed of carbon-based molecules. This group of materials also includes inorganic coordination compounds, which are sometimes referred to as metallo-organic or organometallic compounds. Organics exhibit many technologically important properties, such as magnetic ordering, high electrical conductivity, high- and low-dielectric constants, piezoelectricity, and superconductivity. Like atoms in inorganic materials, dissimilar molecules can be co-crystallized. Although generally thought of as being neutral species, when the electronegativities of co-crystallized molecules are sufficiently different, electron transfer occurs creating anions and cations, and examples can exhibit high direct current electrical conductivity or ferromagnetic ordering. When intermediate differences in the electronegativities occur, charge-transfer complexes form. OXIDES Oxides are materials containing oxygen as a primary anion—examples of current interest are BaTiO3 (a ferroelectric), YBa2Cu3O7 (a superconductor), and La1-xSrxMnO3 (a magnetoresistive material). The wide range of behavior found in metal oxides is due in part to the presence of strong interactions between metal d electrons and oxygen p electrons and a delicate balance between nearly energetically equivalent electronic configurations that involve coupling between electronic,

OCR for page 170
Frontiers in Crystalline Matter: From Discovery to Technology magnetic, and structural degrees of freedom. The presence of oxygen is particularly critical to the creation of exotic properties—the orbital energies of the oxygen ion are well matched to transition metal orbital energies, yielding the added complexity of a balance between covalent and ionic bonding that differs from compound to compound. Finally, the relatively straightforward methods generally used in the synthesis of oxides and their chemical stability make them widely available to the condensed-matter and solid-state chemistry communities, resulting in vigorous worldwide research on many different compound systems. Examples of challenges that drive this field are the quest for room-temperature superconductivity and the production of a room-temperature ferromagnetic insulator. There is also a vigorous effort devoted to realizing qualitatively new magnetic phases such as two-dimensional critical spin liquids. INTERMETALLICS Intermetallics are materials made of combinations of two or more metallic elements. When one of the elements is a magnetic rare-earth or actinide metal (e.g., cerium and uranium), such crystalline systems embody the concentrated limit of the Kondo effect, in which the conduction electron forms a pair with the magnetic ion in a lattice periodic fashion. In this many-body limit, novel “heavy” electron states emerge. These materials constitute the frontier of exploration into the possibility of conducting states of matter that are qualitatively different from the conventional Landau Fermi-liquid, which describes metals such as copper and aluminum. Intermetallic compounds are widely used, though for different reasons, in today’s mechanical and electrical systems.