Barium titanate ceramics thermistors

Attempts are still being made to produce improved bolometers operating at or near room temperature. These include vanadium oxide metal-semiconductor transition devices [8.7], bismuth-lead layers [8.8], metallic nickel [8.8a], and aluminium [8.8b], silicon carbide [8.8c], and doped barium titanate ceramic [8.8d] elements. New designs of radiometers and power meters using thermistor bolometers have been described [8.9-11]. Microelectronic techniques have been used to produce fast but sensitive (NEP 10 WHz at 25 MHz and 100 pm wavelengths) uncooled for improved bolometers [8.11a]. 

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. 

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