Pyroelectric ceramics thin films

Ferroelectric crystals (especially oxides in the form of ceramics) are important basic materials for technological applications in capacitors and in piezoelectric, pyroelectric, and optical devices. In many cases their nonlinear characteristics turn out to be very useful, for example in optical second-harmonic generators and other nonlinear optical devices. In recent decades, ceramic thin-film ferroelectrics have been utilized intensively as parts of memory devices. Liquid crystal and polymer ferroelectrics are utilized in the broad field of fast displays in electronic equipment. 

Pyroelectric Ceramics and Thin Films tion, Properties and Selection... 

There are many different types of pyroelectric, including single crystals, polymers, ceramics and thin films and several reviews [2,3,28,29] have considered the properties of many pyroelectric materials in detail, so the discussion here will be confined to a brief review of pyroelectric ceramics and thin films. 

In conclusion, it has been demonstrated that the pyroelectric properties of polar materials can be compared relatively simply through the measurement of a few key physical parameters (pyroelectric,dielectric and thermal coefficients) and the judicious use of appropriate figures-of-merit. It is essential that the dielectric properties are measured in the frequency range appropriate for device use, and this is typically in the range of a few to 100 Hz. The properties of many pyroelectric ceramics and thin films have been compared and it has been shown that good pyroelectric properties can be obtained from this films manufactured at relatively low temperatures, a fact that bodes well for their future applications in fully-integrated arrays. 

Pyroelectric sensors utilize a wide range of material forms crystals, bulk ceramics, thick layers, and thin films. Noteworthy among new compositions with improved performance is the class of relaxor pyroelectrics. Many novel pyroelectric sensors utilize thin and thick films. Bulk pyroelectric ceramics for room temperature, and pyroelectric sensors, are widely available. New compositions with higher permittivity are available now. 

Ca, Ba, Sr ) into PT ceramics is reported to enhance the pyroelectric properties. Substitution of these ions results in the reduction of lattice anisotropy leading to hard and dense ceramics with high mechanical strength. From the standpoint of thermal responsivity, the performance of a pyroelectric detector is enhanced when it is in the form of a thin film. In recent device applications, it has become increasingly necessary to consider the improvement of these films in then-performance in addition to the large component area and connection to many circuit elements. Recently, calcium- and lanthanum-doped lead... 

WhatniOTe RW (2004) Pyroelectric arrays ceramics and thin films. J Electroceram 13 139-147... 

SBN pyroelectric detector (Liu and Maciolek [3.27]) to Plessey production ceramic pyroelectric detector it Thin film bolometer (Bessonneau [3.15])... 

Both, piezoelectric and pyroelectric behavior is possible only in ferroelectric ceramics, or in otherwise polar materials that are deposited as textured thin films. 

In IR array detectors using pyroelectric materials such as TOS mooocrystal or PbTiO ceramics, the detecting plate must be cut into the array of detector elements in order to reduce the cross-talk of response between adjacent elements, which is caused mainly by high thermal diffusion in the plate. On the other hand, since thin films of pyroelect polymers have low thermal diffusion, linear array detectors [23-25] using polymer film with an array of separated electrodes can have small cross-talk between adjacent elements without cutting the film. 

Table 27.3 Heterostructural characteristics and electrical properties (dielectric, ferroelectric, and pyroelectric) of two (Ca, Pb)Ti03 thin films prepared from the same precursor solutions but crystallized with different thermal annealing rates for the ceramic conversion.

Some LB films exhibit a temperature-dependent pyroelectric coefficient that makes them candidates for thermal imaging applications (1). Both X- and Z-type films and alternating Y-type films (Fig. 6) can be built with permanent polarization, whose magnitude is often temperature-dependent. Their pyroelectric coefficient p is small relative to standard semiconducting and ceramic materials, but so is their permittivity e this makes their ratio p/s, the figure of merit, comparable to that as for currently employed inorganic materials. The advantage of LB methods is that they can be used to prepare very thin, very uniform films. 

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