Insulators thermal expansion coefficient

For use over a wide temperature range, it is necessary to match the thermal expansion coefficients of electrode and insulation sheath. RRDEs of glassy carbon embedded in borosilicate glass for use up to 450° C [123] and gold sputtered on to a chromium or titanium substrate on a Macor ceramic cylinder for use up to at least 125°C [124] are examples. 

Because of the high functional values that polyimides can provide, a small-scale custom synthesis by users or toll producers is often economically viable despite high cost, especially for aerospace and microelectronic applications. For the majority of industrial applications, the yellow color generally associated with polyimides is quite acceptable. However, transparency or low absorbance is an essential requirement in some applications such as multilayer thermal insulation blankets for satellites and protective coatings for solar cells and other space components (93). For interlayer dielectric applications in semiconductor devices, polyimides having low and controlled thermal expansion coefficients are required to match those of substrate materials such as metals, ceramics, and semiconductors used in those devices (94). 

Aluminum nitride is one of the few materials that is both a good thermal conductor and a good electrical insulator. It is also a high-temperature ceramic, that has a low thermal expansion coefficient, and a low dielectric constant. It is also stable to molten metals such as aluminum, has good wear resistance, and good thermal shock resistance. 

The problem of difference in thermal expansion coefficients between a silicon read-out substrate and an HgCdTe detector substrate is approached in US-A-4783594 by filling the space between the two substrates with a resilient electrically insulating polymeric material and thereafter separating the detector elements from each other by removing a layer of the HgCdTe detector substrate. 

Thermal expansion of a semiconductor depends on its microstructure, i.e. stoichiometry, presence of extended defects, ffee-carrier concentration. For GaAs [24] it was shown that for samples of free-electron concentrations of about 1019 cm"3, the thermal expansion coefficient (TEC) is bigger by about 10% with respect to the semi-insulating samples. Different microstructures of samples examined in various laboratories result in a large scatter of published data even for such well known semiconductors as GaP or GaAs. For group III nitrides, compounds which have been much less examined, the situation is most probably similar, and therefore the TECs shown below should not be treated as universal values for all kinds of nitride samples. It is especially important for interpretation of thermal strains (see Datareview A 1.2) for heteroepitaxial GaN layers on sapphire and SiC. 

Certain semiconductor device fabrication methods require the formation of a single-crystal deposit of the semiconductor on an insulating substrate. In epitaxial methods, the semiconductor is deposited on a single-crystal piece of substrate chosen, in part, on the basis of the match of the lattice parameters, thermal expansion coefficients and chemical compatibihty of the substrate and deposit. Singlecrystal substrates include those of AI2O3, MgAl204, Q -quartz andZrSi04. ... 

The substrate was composed of a metal sheet and insulating layers which was coated on the both side of the metal sheet to be prevented fi om warping. Al-doped ferritic stainless steel (0.2 mm in thickness) was selected for the metal sheet. Because the value of liner thermal expansion coefficient of it (1.0 X10 K ) was in good agreement with that of iron silicide... 

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 influence 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. 

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