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Semiconduction BaTiO

In the temperature region 1(T < Tc), the resistivity of PTC thermistor is in the range of 10-10 cm. To produce semiconductive BaTiOs, a small amount of rare earth metal ions (e.g. Sm + or La +) are substituted at the Ba + site, or Nb and Ta " " ions are substituted at the Ti site. These ions provide conductive electrons as shown in the following equations, using the defect notation of Kroger and Vink. [Pg.26]

Macdonald J.R., L.D.P. A flexible procedure for analyzing impedance spectroscopy results— description and illustrations. Solid State Ionics 1987 24 61-79 Maissel L.I. Electrical properties of metallic thin films. In Handbook of Thin Film Technology, Maissel L.I., Glang R., ed. New York McGraw-Hill, 1970, pp. 13/11—33 Matsuda H., Mizushima T, Kuwabara M. Low-temperature synthesis and electrical properties of semiconducting BaTiOs ceramics by the sol-gel method with high concentration alkoxide solutions. J. Ceram. Soc. Jap. 1999 107 290-292... [Pg.1162]

Standard ceramic processing conditions are controlled so that the resulting ceramic microstmcture is composed of semiconducting 2inc oxide grains (pZnO < IHcm) and electrically insulating grain boundaries > 10 0cm)). The microstmcture is thus similar to that of the BaTiO thermistor and... [Pg.346]

Oxides play many roles in modem electronic technology from insulators which can be used as capacitors, such as the perovskite BaTiOs, to the superconductors, of which the prototype was also a perovskite, Lao.sSro CutT A, where the value of x is a function of the temperature cycle and oxygen pressure which were used in the preparation of the material. Clearly the chemical difference between these two materials is that the capacitor production does not require oxygen partial pressure control as is the case in the superconductor. Intermediate between these extremes of electrical conduction are many semiconducting materials which are used as magnetic ferrites or fuel cell electrodes. The electrical properties of the semiconductors depend on the presence of transition metal ions which can be in two valence states, and the conduction mechanism involves the transfer of electrons or positive holes from one ion to another of the same species. The production problem associated with this behaviour arises from the fact that the relative concentration of each valence state depends on both the temperature and the oxygen partial pressure of the atmosphere. [Pg.236]

Kim, J.-S. and Kang, S.-J. L., Grain boundary migration and dielectric properties of semiconducting SrTiOs in the SrTiOs-BaTiOs-CaTiOs system, J. Am. Ceram. Soc., 82, 1196 200, 1999. [Pg.133]

The information about nanocrystalline ferroic powders fabricated by various chemical synthesis technologies is reported in Table 5.2. Their possible applications are also listed. Powders of the same ferroics for two different applications might be obtained by different techniques since the requirements of size distribution, morphology, agglomeration and impurity composition are determined by different technological conditions. For example, barium titanate is a dielectric with high dielectric constant and it is widely used in multilayer ceramic capacitors, whereas semiconducting properties of rare-earth doped BaTiOs are important for thermistors. [Pg.301]

Titanates are double oxides of the form MeTiOa or Me2Ti04. Barium titanate BaTiOa and its solid solution crystals with other titanates are especially well-known. BaTiOs crystallizes in the perovskite structure. Its technical importance results from its ferroelectric and associated piezoelectric properties, its high dielectric constant at room temperature, and the interesting semiconducting properties which it exhibits when doped [13]. The remarkable temperature dependence of the electrical resistance of such doped material (the temperature coefficient can be metal-like) is used to advantage in control and circuit devices. [Pg.173]

The resistivity changes of the Ca-doped and undoped BaTiOs as a function of mole ratio m are shown in Figure 5.1.4. All the samples which were sintered in air exhibited high insulation resistance and were independent of Ca content and molar ratio m. However, the samples, which had a molar ratio less than 1.00, were considerably reduced, and became semiconducting when fired under a low PiOj) atmosphere. [Pg.165]

Class 3 capacitors are based on either BaTiOs or SrTiOs (usually X7R type) and have very high apparent dielectric constants (k = 50,000-100,000), which are achieved by producing either a surface layer on the grains or at the GBs that is electrically insulating while the grains themselves are conducting or semiconducting. This can be achieved in two ways ... [Pg.566]


See other pages where Semiconduction BaTiO is mentioned: [Pg.548]    [Pg.128]    [Pg.349]    [Pg.361]    [Pg.595]    [Pg.3]    [Pg.550]    [Pg.534]    [Pg.566]    [Pg.698]    [Pg.25]    [Pg.534]   
See also in sourсe #XX -- [ Pg.3 , Pg.167 , Pg.327 ]




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