Single Crystal Ceramics

MgO was mentioned in Chap. 5, Sect. 5.2.2 as being ductile at ambient temperature, thus undergoing plastic deformation. Having a high melting point of 2798 °C, it is expected that creep may occur at high homologous temperatures. In 

The creep substmctunes in annealed (110) MgO single crystals show that no sub grains were formed during tensile creep at 1400 °C. The 1800 °C true-llow stress at 10 % strain increased with the increasing strain rate (i.e., 25.5, 55.3, and 71.6 MNm for strain rates of 0.002, 0.02, and 0.2 min , respectively). Note that inducing a substructure, which produces various arrays of dislocations, is equivalent to the effect of stress (as indicated in Fig. 6.2b). 

The unique nature (plasticity and creep deformation) of SrTi03 also merits discussion. Quite surprisingly, this ceramic, unlike most ceramics, can be plastically deformed (under compression) in the temperature ranges 78—1050 K and 1050-1500 K, although it acts in abrittle fashion [31]. Here, the rare phenomenon 

This analysis was performed as usual for the evaluation of values of interest. Based on Eq. (6.4), the exponent and activation energies are rewritten as  

Only runs reaching steady-state creep have been completed numberes in parantheses are estimated errors 

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Sihcon carbide has been described as a mild inhalation irritant (143). The threshold limit value for siUcon carbide in the atmosphere is 5 mg/m. Because of increased interest in SiC whiskers as a reinforcement for composites, the ASTM has estabUshed Subcommittee E34.70 on Single-Crystal Ceramic Whiskers to write standards for handling this form of SiC (144). 

Microwave properties of dielectric single crystals, ceramics and thin films... 

Type Single crystal Single crystal Ceramic Ceramic Ceramic... 

Single-crystal ceramics also fracture (Figure 16.1 shows an Nd-doped YAG single-crystal boule that fractured during growth). 

Fig. 8.6 Illustration of the production of single-crystal ceramic material by the sintering (nonmelting) conversion method. Reproduced with permission from [61]. Copyright 2007,...

The TCE of most ceramics is isotropic, although for certain crystalline or single-crystal ceramics, the TCE may be anisotropic, and some may even contract in one direction and expand in the other. Ceramics used for substrates do not generally fall into this category, as most are mixed with glasses in the preparation stage and do not exhibit anisotropic properties as a result. The temperature coefficient of expansion of several ceramic materials is shown in Table 4.5. This parameter is linear over the temperature range of interest. 

In order to detect amorphization of crystalline samples after ion beam irradiation, RBS under channeling conditions is a very useful tool 95. often applied to inve.stigations of semiconductors and single-crystal ceramic samples or of diamond. 

ConcBpt Check 19.3 The thermal conductivity of a single-crystal ceramic specimen is slightly greater than that of a polycrystalline one of the same material. Why is this so ... 

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