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| Names | |
|---|---|
| IUPAC name Glycine sulfate (3:1) | |
| Other names Glycine sulfate; TGS | |
| Identifiers | |
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3D model (JSmol) | |
| ChemSpider | |
| ECHA InfoCard | 100.007.414 |
| EC Number |
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| UNII | |
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| Properties | |
| C6H17N3O10S | |
| Molar mass | 323.27 g·mol−1 |
| Appearance | White powder |
| Density | 1.69 g/cm3[1] |
| Structure | |
| Monoclinic | |
| P21[2] | |
a = 0.9417 nm,b = 1.2643 nm,c = 0.5735 nm α = 90°, β = 110°, γ = 90° | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Triglycine sulfate (TGS) is a chemical compound with a formula (NH2CH2COOH)3·H2SO4. The empirical formula of TGS does not represent the molecular structure, which contains protonated glycine moieties andsulfate ions. TGS with protons replaced by deuterium is called deuterated TGS orDTGS; alternatively, DTGS may refer to doped TGS. By doping the DTGS with the amino acid L-Alanine, the crystal properties are improved and the new material is called Deuterated L-Alanine doped Triglycine Sulfate (DLATGS orDLTGS). These crystals arepyroelectric andferroelectric which allows their use asphotodetector elements ininfrared spectroscopy and night vision applications.[3] TGS detectors have also been used as the target invidicon cathode ray imager tubes.
TGS has a critical point for the order parameter of polarization, at 322.5 K.[4]
TGS crystals may be formed by evaporation of an aqueous solution ofsulfuric acid and a greater than three-fold excess ofglycine.[5] They belong to thepolarspace group P21 and therefore are pyroelectric and ferroelectric at room temperature, exhibiting spontaneous polarization along theb-axis ([010] direction). TheCurie temperature of the ferroelectric transition is 49 °C for TGS and 62 °C for DTGS. The crystal structure consists of SO42−, 2(N+H3CH2COOH) (G1 and G2 in the crystal-structure diagram), and+NH3CH2COO− (G3) species held together byhydrogen bonds.[6] These bonds are easily broken by the polar molecules of water, which leads to thehygroscopicity of TGS – its crystals are easily etched by water. Along theb-axis, the G1-SO4 and G2-G3 layers are stacked alternately. The nearest two neighboring layers with identical chemical composition are rotated 180° around theb-axis against each other.[2][7] DTGS and DLATGS materials are derivatives of TGS which have better pyroelectric properties and give less detector noise as can be shown in the following table.
| Material | TGS | DTGS | DLATGS |
| Doping | - | D2O as a solvent | 20% wt. L-Alanine |
| Temperature of measurement (°C) | 25 | ||
| Curie temperature (°C) | 49 | 57-62 | 58-62 |
| Dielectric Constant at 1 kHz | 22-35 | 18-22.5 | 18-22 |
| Spontaneous Polarization (μC/cm2) | 2.75 | 2.6 | - |
| Coercive electric field (V/cm) | 165 V/cm | ||
| Inherent bias field (kV/cm) | 0.664-5 | 0.664-5 | 2-5 |
| Dielectric loss tan δ | ~1×10−3-10×10−3 | ||
| Figure of Merits (FOMs) Fi =p (nC/cm2.oK) FV =p/ε´ (nC/cm2.oK) FD =p/√ε ′′ (nC/cm2.oK) | 16-45 0.5-1.14 0.4-121 | 25-70 1.4 - | 25 1.13 - |
| Volume Specific Heat (J/ cm3.oK) | 2.5 | 2.5 | 2.7 |
| Density (g/cm3) | 1.66 | 1.7 | 1.7 |
| AC Resistivity at 1 kHz (Ω.cm×1010) | 1.7 | 5 | 2.4 |
The typical performance and pyroelectric properties of DLATGS detectors of 1.3 and 2.0 mm in diameter of the element size are shown in the table below.
| Element size (mm) | Vout at 1 kHz | Voltage responsivity V/W at 1 kHz | Vn at 1 kHz (1 Hz BW) | D* at 1 kHz Detectivity (cmHz1/2/W) | C (pF) | tan δ | NEP (W/√Hz) | |
| 1.3 | Typical | 3.20E-5 | 50 | 3.00E-8 Maximum | 2.70E+8 | 10.6 (at 20 μm) | 0.003 | 4.50E-10 |
| 2.0 | Typical | 3.20E-5 | 30 | 2.00E-8 Maximum | 3.50E+8 | 25 (at 25 μm) | 0.003 | 4.50E-10 |
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