Ceramic and Glass Materials

J.F. Shackelford and R.H. Doremus (eds.), Ceramic and Glass Materials: 87

Structure, Properties and Processing.

© Springer 2008

Chapter 6

Refractory Oxides

Jeffrey D. Smith and William G. Fahrenholtz

Abstract Refractory oxides encompass a broad range of unary, binary, and ternary
ceramic compounds that can be used in structural, insulating, and other applications.
The chemical bonds that provide cohesive energy to the crystalline solids also influ-
ence properties such as thermal expansion coefficient, thermal conductivity, elastic
modulus, and heat capacity. This chapter provides a historical perspective on the use
of refractory oxide materials, reviews applications for refractory oxides, overviews
fundamental structure–property relations, describes typical processing routes, and
summarizes the properties of these materials.

1 Introduction

The term refractory refers to materials that are resistant to the effects of heat.

Refractory oxides, therefore, are ceramic materials that can be used at elevated

temperatures. These nondescript restrictions allow nearly any oxide to be classified as

refractory. For this article, refractory oxides will refer, somewhat arbitrarily, to common

crystalline compounds with melting temperatures of at least 1,800°C. These compounds

can contain one or more metal or metalloid cations bonded to oxygen. As an introduc-

tion to the topic, this section provides a brief historic overview of materials commonly

used in the refractories industry, including some lower melting temperature materials.

The section also reviews some current trends in the industries that produce and use

refractory oxides. The other sections of this chapter focus on phase-pure oxide ceramics

that can be used at elevated temperatures.

Historically, most of the oxides that were used in refractory applications were

traditional ceramics prepared from clays or other readily available mineral-based

raw materials. The major categories of traditional refractories are fire clays, high

aluminas, and silica [1]. The choice of material for traditional refractory applica-

tions, as with advanced material applications, was and is based on balancing cost

and performance/lifetime. The ultimate use temperatures and applications for some

common refractories are summarized in Table 1 [2, 3]. The production, properties,

and uses of some of these materials are discussed in more detail in the other chapters