Thin-film ceramic materials, importance

Thin film ceramic materials with important magnetic, optical, electronic, and mechanical properties are often highly anisotropic. Thus, the ability to control orientation is critically important in thin film applications. For many of the oxide materials, as well as Ae ionic materials, aqueous solution or sol-gel routes are the most convenient or the only method of preparation. Examples of these include barium titanate (BaTiOs) used in multilayer capacitors, lead-zirconate-titanate (Pb(Zr,Ti)03, "PZT") used as a piezoelectric material, and zinc oxide (ZnO) used in varistors. Thus, the use of substrates to control orientation can eliminate major problems in deposition of thin films. In some cases, e.g., the many magnetic and non-magnetic phases of iron oxide, the ability to control the phase formed is critical to production of the desired properties. While this can be controlled by solution conditions, the proper surface can add an additional and very effective mechanism of control. 

XPS has been used in almost every area in which the properties of surfaces are important. The most prominent areas can be deduced from conferences on surface analysis, especially from ECASIA, which is held every two years. These areas are adhesion, biomaterials, catalysis, ceramics and glasses, corrosion, environmental problems, magnetic materials, metals, micro- and optoelectronics, nanomaterials, polymers and composite materials, superconductors, thin films and coatings, and tribology and wear. The contributions to these conferences are also representative of actual surface-analytical problems and studies [2.33 a,b]. A few examples from the areas mentioned above are given below more comprehensive discussions of the applications of XPS are given elsewhere [1.1,1.3-1.9, 2.34—2.39]. 

The importance of materials science to U.S. competitiveness can hardly be overstated. Key materials science areas underlie virtually every facet of modem life. Semiconductors underpin our electronics industry. Optical fibers are essential for communications. Superconducting materials will probably affect many areas ceramics, composites, and thin films are having a big impact now in transportation, construction, manufacturing, and even in sports—tennis rackets are an example. 

Ceramic materials in contact with aqueous liquids are also susceptible to attack. This is of particular importance in the realm of civil engineering, where materials of con-strnction that contain minerals routinely come in contact with groundwater and soil. Minerals dissolve into aqueous solutions through the diffusion of teachable species into a stationary thin film of water, about 110 ttm thick... 

It is important to realize that thin films may differ in some substantial ways from bulk ceramics or single crystals of the same composition. One source of these differences is the substantial in-plane stresses that thin films are typically under, ranging from MPa to GPa [9], Because many ferroelectric materials are also ferroelastic, imposed stresses can markedly affect the stability of the ferroelectric phase, as well as the ease with which polarization can be reoriented in some directions. The phase diagram becomes considerably complicated by the presence of a dissimilar substrate [10]. It is obvious that the material coefficients are drastically changed. 

Table 5.1 Microwave properties of the most important microwave dielectrics (SC= bulk single crystals , bc = bulk ceramics , tf = thin films , r/ = temperature coefficient of resonant frequency . The materials marked with are tuneable dielectrics.

The power of laser ablation can be extended as a popular method for trace and bulk analysis in conjunction with ICP-OES and is an invaluable tool in the study of surface behaviour particularly where sensitive surfaces are important. The common area for surface knowledge is in environment, medicines, adhesives, powders, slurries, oil-based samples and liquids. It finds application in the analysis of metallurgical samples, non-conductive polymers, ceramic materials, surface mapping, elemental migration, depth profiling, thin film coatings, biological and clinical specimens, forensic, paint chips, inks, bullets, fabrics, etc. 

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