Copyright © 2015 by John Wiley & Sons, Inc. All rights reserved
Published by John Wiley & Sons, Inc., Hoboken, New Jersey
Published simultaneously in Canada
No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permissions.
Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.
For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at www.wiley.com.
Library of Congress Cataloging-in-Publication Data:
Rao, C.N.R. (Chintamani Nagesa Ramachandra), 1934– author.
Essentials of inorganic materials synthesis / C.N.R. Rao, Kanishka Biswas.
pages cm
Includes bibliographical references and index.
ISBN 978-1-118-83254-7 (hardback)
1. Inorganic compounds–Synthesis. I. Biswas, Kanishka, author. II. Title.
QD156.R36 2014
541′.39–dc23
2014035381
C.N.R. Rao obtained his Ph.D. degree from Purdue University (1958) and D.Sc. degree from the University of Mysore (1961). He is the National Research Professor and Linus Pauling Research Professor at the Jawaharlal Nehru Centre for Advanced Scientific Research and Honorary Professor at the Indian Institute of Science (both at Bangalore). His research interests are mainly in the chemistry of materials. He is a fellow of the Royal Society, London, a foreign associate of the US National Academy of Sciences and a member of many other science academies. He is the recipient of the Einstein Gold Medal of UNESCO, the Hughes and Royal Medals of the Royal Society, the August Wilhelm von Hofmann medal of the German Chemical Society, the Dan David Prize and the Illy Trieste Science prize for materials research and the first India Science Prize.
Kanishka Biswas obtained his Ph.D. degree from Solid State Structural Chemistry Unit, Indian Institute of Science, India (2009), and did his postdoctoral research from Department of Chemistry, Northwestern University, USA (2009–2012). He is now a Assistant Professor (Faculty Fellow) in the New Chemistry Unit of Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India. He is an Associate of Indian Academy of Sciences, Bangalore. He is pursuing research in solid-state chemistry of metal chalcogenides and thermoelectric ‘waste heat to electrical energy conversion’.
Chemical methods of synthesis play a crucial role in designing and discovering novel materials, especially metastable ones which cannot be prepared otherwise. They often provide better and less cumbersome methods for preparing known materials. There is a tendency nowadays to avoid brute-force methods and instead employ methods involving mild reaction conditions. Soft-chemistry routes are indeed becoming popular and will continue to be pursued greatly in the future. In view of the increasing importance of materials synthesis, we considered it appropriate to provide a proper account of the chemical methods of synthesis of inorganic materials in a book.
John Wiley had published a small monograph written by the first author of this book entitled Chemical Approaches to the Synthesis of Inorganic Materials some years ago (1994). We felt the need for a book which was more complete and yet handy, covering most of the synthetic methods employed by chemists and materials scientists. We believe that the present work answers such a need.
In this book, we briefly examine the different types of reactions and methods employed in the synthesis of inorganic solid materials. Besides the traditional ceramic procedures, we discuss precursor methods, combustion method, topochemical reactions, intercalation reactions, ion-exchange reactions, alkali-flux method, sol–gel method, mechanochemical synthesis, microwave synthesis, electrochemical methods, pyrosol process, arc and skull methods and high-pressure methods. Hydrothermal and solvothermal syntheses are discussed separately and also in sections dealing with specific materials. Superconducting cuprates and intergrowth structures are discussed in separate sections. Synthesis of nanomaterials is dealt with in some detail. Synthetic methods for metal borides, carbides, nitrides, fluorides, silicides, phosphides and chalcogenides are also outlined.
While this book is not expected to serve as a laboratory guide, it is our hope that it provides an up-to-date account of the varied aspects of chemical synthesis of inorganic materials and serves as a ready reckoner as well as a guide to students, teachers and practitioners. The key references cited in the monograph would help to obtain greater details of preparative procedures and related aspects.
Much chemical ingenuity is involved in the synthesis of solid materials [1–6] and this aspect of material science is getting increasingly recognized as a crucial component of the subject. Tailor-making materials of the desired structure and properties is the main goal of material science and solid-state chemistry, but it may not always be possible to do so. While one can evolve a rational approach to the synthesis of solid materials [7], there is always an element of serendipity, encountered not so uncommonly. A good example of an oxide discovered in this manner is NaMo4O6 (Fig. 1.1) containing condensed Mo6 octahedral metal clusters [8]. This was discovered by Torardi and McCarley in their effort to prepare the lithium analogue of NaZn2Mo3O8. Another chance discovery is that of the phosphorus–tungsten bronze, RbxP9W32O112, formed by the reaction of phosphorus present in the silica of the ampoule, during the preparation of the Rb–WO3 bronze [9]. Since the material could not be prepared in a platinum crucible, it was suspected that a constituent of the silica ampoule must have got incorporated. This discovery led to the synthesis of the family of phosphorus–tungsten bronzes of the type AxP4O8 (WO3)2m. Chevrel compounds of the type AxMO6S8 (A = Cu, Pb, La etc.) shown in Figure 1.2 were also discovered accidentally [10].
Rational synthesis of materials requires knowledge of crystal chemistry besides thermodynamics, phase equilibria and reaction kinetics. There are several examples of rational synthesis. A good example is SIALON [11], where Al and oxygen were partly substituted for Si and nitrogen in Si3N4. The fast Na+ ion conductor NASICON, Na3Zr2PSi2O12 (Fig. 1.3), was synthesized with a clear understanding of the coordination preferences of the cations and the nature of the oxide networks formed by them [12]. The zero-expansion ceramic Ca0.5Ti2P3O12 possessing the NASICON framework was later synthesized based on the idea that the property of zero-expansion would be exhibited by two or three coordination polyhedra linked in such a manner as to leave substantial empty space in the network [7]. Synthesis of silicate-based porous materials, making use of organic templates to predetermine the pore or cage geometries, is well known [13]. A microporous phosphate of the formula (Me4N)1.3(H3O)0.7 Mo4O8(PO4)2⋅2H2O, where the tretramethyl–ammonium ions fill the voids in the 3-dimensional structure made up of Mo4O8 cubes and PO4 tetrahedra, has been prepared in this manner [14].
A variety of inorganic solids have been prepared in the past several years by the traditional ceramic method, which involves mixing and grinding powders of the constituent oxides, carbonates and such compounds, and heating them at high temperatures with intermediate grinding when necessary. A wide range of conditions, often bordering on the extreme, such as high temperatures and pressures, very low oxygen fugacities and rapid quenching, have been employed in material synthesis. Low-temperature chemical routes and methods involving mild reaction conditions are, however, of greater interest. The present-day trend is to avoid brute-force methods in order to get a better control of the structure, stoichiometry and phasic purity. Soft-chemistry routes, which the French call chimie douce, are indeed desirable because they lead to novel products, many of which are metastable and cannot otherwise be prepared. Soft-chemistry routes essentially make use of simple reactions such as intercalation, ion exchange, hydrolysis, dehydration and reduction that can be carried out at relatively low temperatures. The topochemical nature of certain solid-state reactions is also exploited in synthesis. Ion exchange, intercalation and many other types of reactions are generally topochemical.
Many of the materials that are prepared are metastable. Metastable phases possess higher free energy than the corresponding stable phases of the same composition. Metastability can arise from frozen disorder and/or defects (e.g. glasses, ionic conductors). Topological metastability is found in porous materials including zeolites. Nanocrystals of many materials crystallize in metastable structures due to the excess surface free energy. Kinetics determine the evolution of structures in many instances and the metastable phases are favoured when the system is far from a state of equilibrium. In the case of zeolitic materials or aluminosilicates, the dense phases are thermodynamically stable, but the useful phases are less dense, porous and metastable. Metastable materials are often formed by quenching from high temperature or pressure, or by using soft-chemical routes. Atomic layer deposition or layer-by-layer deposition can be used to prepare metastable structures.
In the sections that follow, we briefly discuss the synthesis of inorganic solids by various methods with several examples, paying attention to the chemical routes. While oxide materials occupy a great part of the monograph, other classes of materials such as chalcogenides, carbides, fluorides and nitrides are also discussed. Superconducting oxides, intermetallics, porous materials and intergrowth structures have been discussed in separate sections. We have added a new section on nanomaterials.