Phase transitions in lead zirconate-titanate and their applications in thermal detectors

Clarke, Roy; Glazer, A. M.; Ainger, F. W.; Appleby, Daniel J. R.; Poole, N. J.; Porter, Stephen G.

doi:10.1080/00150197608236581

Cited by 64 publications

(13 citation statements)

References 5 publications

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“…2b). This combination of properties favours its use in pyroelec~ric detectors (Clarke & Glazer 1976a;Clarke, Glazer, Ainger, Appleby, Poole & Porter, 1976). The three phases of PbZr0.gTi0.~O 3 are summarized in Table 1.…”

Section: Introductionmentioning

confidence: 99%

Powder profile refinement of lead zirconate titanate at several temperatures. I. PbZr_0.9Ti_0.1O₃

Glazer¹,

Mabud²,

Clarke³

1978

Acta Crystallogr B Struct Sci

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165

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Section: Introductionmentioning

confidence: 99%

Powder profile refinement of lead zirconate titanate at several temperatures. I. PbZr_0.9Ti_0.1O₃

Glazer¹,

Mabud²,

Clarke³

1978

Acta Crystallogr B Struct Sci

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165

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“…p Dielectric c' There have been various experiments to try to improve the figures of merit of modified PZ compositions. One prospect is through exploitation of the step in the spontaneous polarisation at the F R(LT) to F R(HT) phase transition [19]. This leads to a significant increase in the pyroelectric coefficient over a relatively narrow temperature range, with very little change to the dielectric permittivity or loss in the same range.…”

Section: Methodsmentioning

confidence: 99%

Pyroelectric IR sensor arrays for fall detection in the older population

2005

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Uncooled pyroelectric sensor arrays have been studied over many years for their uses in thermal imaging applications. These arrays will only detect changes in IR flux and so systems based upon them are very good at detecting movements of people in the scene without sensing the background, if they are used in staring mode. Relatively-low element count arrays (16 x 16) can be used for a variety of people sensing applications, including people counting (for safety applications), queue monitoring etc. With appropriate signal processing such systems can be also be used for the detection of particular events such as a person falling over. There is a considerable need for automatic fall detection amongst older people, but there are important limitations to some of the current and emerging technologies available for this. Simple sensors, such as 1 or 2 element pyroelectric infra-red sensors provide crude data that is difficult to interpret; the use of devices worn on the person, such as wrist communicator and motion detectors have potential, but are reliant on the person being able and willing to wear the device; video cameras may be seen as intrusive and require considerable human resources to monitor activity while machine-interpretation of camera images is complex and may be difficult in this application area. The use of a pyroelectric thermal array sensor was seen to have a number of potential benefits. The sensor is wall-mounted and does not require the user to wear a device. It enables detailed analysis of a subject's motion to be achieved locally, within the detector, using only a modest processor. This is possible due to the relative ease with which data from the sensor can be interpreted relative to the data generated by alternative sensors such as video devices. In addition to the cost-effectiveness of this solution, it was felt that the lack of detail in the low-level data, together with the elimination of the need to transmit data outside the detector, would help to avert feelings intrusiveness on the part of the end-user. The main benefits of this type of technology would be for older people who spend time alone in unsupervised environments. This would include people living alone in ordinary housing or in sheltered accommodation (apartment complexes for older people with local warden) and non-communal areas in residential/nursing home environments (e.g. bedrooms and ensuite bathrooms and toilets). This paper will review the development of the array, the pyroelectric ceramic material upon which it is based and the system capabilities. It will present results from the Framework 5 SIMBAD project, which used the system to monitor the movements of elderly people over a considerable period of time.

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“…One prospect is through exploitation of the step in the spontaneous polarisation at the F R(LT ) to F R(H T ) phase transition [21]. This leads to a significant increase in the pyroelectric coefficient over a relatively narrow temperature range, with very little change in the dielectric permittivity or loss in the same range.…”

Section: Pyroelectric Ceramicsmentioning

confidence: 99%

Pyroelectric Arrays: Ceramics and Thin Films

Whatmore

2004

J Electroceram

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Pyroelectric infra-red detectors have been of-interest for many years because of their wide wavelength response, good sensitivity and lack of need for cooling. They have achieved a wide market acceptance for such applications as people sensing, IR spectrometry (especially for environmental protection) and flame/fire protection. Arrays of such detectors, comprising a pyroelectric material interfaced to an application specific integrated circuit for signal amplification and read out, provide an attractive solution to the problem of collecting spatial information on the IR distribution in a scene and a range of new applications are appearing for such devices, from thermal imaging to people sensing and counting. The selection of the best material to use for such a device is very important. Because all polar dielectrics are pyroelectric, there is a very wide range of such materials to choose. The performance of a pyroelectric IR sensor array can be derived from the physics of their operation and figures-of-merit (FoM) defined that will describe the performance of a material in a device, in terms of its basic pyroelectric, dielectric and thermal properties. These FoM and their appropriateness for the array application are reviewed. Large arrays of small detectors are best served by the use of pyroelectric materials with permittivities between 200 and 1000, depending upon the element size and the element thermal conductance, and a maximised FoM F D = p{c (εε o tan δ) 1/2 }. Such properties are found in ferroelectric perovskite ceramics and a wide range have been explored for their use in pyroelectric arrays. These include materials based on compositions in the PbZr x Ti 1−x O 3 (PZT) system, for example close to PbZrO 3 , with Curie temperatures well above ambient. Examples of the ways in which these materials can be modified by doping to optimise their FoM and other important properties such as electrical resistivity are given and the physics operating behind this discussed. The performances and costs of uncooled pyroelectric arrays are ultimately driven by the materials used. For this reason, continuous improvements in materials technology are important. In the area of bulk ceramics, it is possible to obtain significant improvements in both production costs and performance though the use of tape-cast, functionally-gradient materials. Finally, the use of directly-deposited ferroelectric thin films on silicon ASIC's is offering considerable potential for low cost high performance pyroelectric arrays. The challenges involved in developing such materials will be discussed, especially from the aspect of low temperature deposition and other fabrication issues, such as patterning. Sol gel deposition provides an excellent technique for thin film growth and Mn-doped PZT films can be grown at 560 • C with a FoM F D exceeding those of many bulk materials.

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Phase transitions in lead zirconate-titanate and their applications in thermal detectors

Cited by 64 publications

References 5 publications

Powder profile refinement of lead zirconate titanate at several temperatures. I. PbZr_0.9Ti_0.1O₃

Powder profile refinement of lead zirconate titanate at several temperatures. I. PbZr_0.9Ti_0.1O₃

Pyroelectric IR sensor arrays for fall detection in the older population

Pyroelectric Arrays: Ceramics and Thin Films

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Phase transitions in lead zirconate-titanate and their applications in thermal detectors

Cited by 64 publications

References 5 publications

Powder profile refinement of lead zirconate titanate at several temperatures. I. PbZr0.9Ti0.1O3

Powder profile refinement of lead zirconate titanate at several temperatures. I. PbZr0.9Ti0.1O3

Pyroelectric IR sensor arrays for fall detection in the older population

Pyroelectric Arrays: Ceramics and Thin Films

Contact Info

Product

Resources

About

Powder profile refinement of lead zirconate titanate at several temperatures. I. PbZr_0.9Ti_0.1O₃

Powder profile refinement of lead zirconate titanate at several temperatures. I. PbZr_0.9Ti_0.1O₃