Triglycine sulfate pyroelectric

Figure 7.4. Ratio of the NEPs of a triglycine sulfate pyroelectric bolometer of the type used on early FT-IR spectrometers and a thermocouple of the type used on grating spectrometers. The mirror velocity for the interferometer was 1.58 mm s (5-kHz laser frequency). (Reproduced from [9], by permission of the Society for Applied Spectroscopy copyright 1977.)...

Pyroelectric detectors depend on the use of a thin slice of ferroelectric material (deuterated triglycine sulfate [DTGS], Figure 5.6, is the standard example) - in which the molecules of the organic crystal are naturally aligned with a permanent electric dipole. The thin slab is cut and arranged such that the direction... 

The modulated beam is directed through either the sample or reference side of the sample compartment and is finally focused on the detector. For most mid-infrared work, a triglycine sulfate (TGS) pyroelectric bolometer is used as the detector because of its very high frequency response (> 1 MHz). 

The OMA technology has been recently applied to infra-red spectroscopy ( 18) as well. A pyroelectric vidicon (utilizing a triglycine sulfate as the sensor element) has been used as a thermal rather than a photon multichannel detector. Simultaneous spectral detection, in the 1-30 um spectral region, was accomplished that has proven to be particularly useful for IR pulse laser applications, Fig.12,... 

Pyroelectric detectors are manufactured from crystals of a pyroelectric material, such as barium titanate or triglycine sulfate. When a crystal of either of these compounds is sandwiched between a pair of electrodes (one of which is transparent... 

Fourier transform IR instruments contain no dispersing element, and all wavelengths are detected and measured simultaneously. Instead of a monochromator, an interferometer is used to produce interference patterns that contain the infrared spectral information. The. same types of sources used in dispersive instruments are used in FTIR spectrometers. Transducers are typically triglycine sulfate—a pyroelectric transducer—or mercury cadmium telluride—a photoconductive trans-... 

The pyroelectric detector contains a mono-crystal of deuterated triglycine sulfate (DTGS) or lithium tantalate (LiTaOj), sandwiched between two electrodes, one of which is semi-transparent to radiation and receives the impact of the optical beam. It generates electric charges with small temperature changes. The crystal is polarized proportionally to the radiation received and it acts as a capacitor. 

Pyroelectric transducers are constructed from single crystalline wafers of pyroelectric materials, which are insulators (dielectric materials) with very special thermal and electrical properties. Triglycine sulfate (NH7CH2COOH), H. SOt (usually dcutcraicd or with a fraction of the glycines replaced with alanine), is the most important pyroelectric material used for IR-detcction systems. 

The standard detector in routine FT-IR instruments is the pyroelectric DTGS (deut-erated triglycine sulfate) detector, whose response in the MIR range is wavelength independent. The detector operates at ambient temperature and shows good linearity across the whole transmittance scale. The DTGS detector responds to signal frequencies of up to several thousand Hz, hence the time needed to scan one spectrum at a resolution of 4 cm is of the order of 1 s. 

Pyroelectric materials exhibit a spontaneous polarization that is a strong function of temperature because the dipole moments vary as the crystal expands or contracts. This was observed in the mineral tourmaline in the seventeenth century. Pyroelectricity occurs in organic crystals such as triglycine sulfate (TGS), ceramics such as... 

Pyroelectric materials are an active material in pyroelectric detectors (Norkus et al. 2006 Budzier and Gerlach 2011). Parameters of these materials are listed in Table 14.18. The three most connmonly used pyroelectric materials in such detectors are triglycine sulfate (TGS), lithium tantalate, and ceramic material based on lead zirconate (PZ), including lead zirconate titanate (PZT) (Porte 1987 Izyumskaya et al. 2007). 

An infrared detector converts the incident infrared radiation to electric signals. If the electric signal from a detection system (a detector and associated electronics) is not proportional to the intensity of the incident infrared radiation, in other words, if the detector response is nonlinear, this nonlinearity causes distortion in the measured interferogram. As a result, the infrared spectrum calculated from the distorted interferogram has inaccurate intensities, which may lead to deviations from Lambert-Beer s law. Such nonlinearity does not occur with a detection system with a pyroelectric TGS (triglycine sulfate) detector, but it may arise in the detection system with a photoconductive MCT detector. 

---