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The dielectric and pyroelectric performances of 91.5 Na 0. 5 Bi 0. 5 TiO3–8.5 K 0. 5 Bi 0. 5 TiO3 lead-free single crystal were investigated. The depolarization temperature of the crystal is about 153 ∘ C. Among the <001>, <110>, and <111> crystallographic orientations, the <111>-oriented crystal possesses the highest pyroelectric coefficient and the largest figures of merit, and the values of p , F v , and F d are 5.63×10 − 4 C/m2 •K, 0.06 m2/C, and 21.5 μ Pa − 1 / 2 for the <111>-oriented crystal at room temperature. The F d and F v exhibit weak frequency dependence in the range of 100–300 Hz. With the increase of the temperature, the value of p increases, while the value of F v decreases from 18 ∘ C to 103 ∘ C. [ABSTRACT FROM AUTHOR]

Single crystals based on solid solutions of lead-magnesium-niobate (PMN) and lead titanate (PT) have emerged as highly promising multifunctional systems combining piezoelectric, pyroelectric, and electro-optic properties that surpass by far those of the best known lead-zirkonium-titanate ceramics. In this paper we present new findings on how the phase transition temperature and the dielectric and ferroelectric properties can be tuned depending on crystal composition, orientation, and thermoelectrical treatment. Mn-doped and pure 0.72PbMg1/3Nb2/3O3-0.28PbTiO3 (0.72PMN-0.28PT) single crystals with <111> and <001> orientations were investigated. A special attention was devoted to field cooling (FC), i.e., cooling under electric field from different temperatures. The results illustrate different findings that were not reported before: the Curie temperature, i.e., ferroelectric-paraelectric transition temperature, is enhanced after field cooling of the Mn-doped, <001>-oriented crystal while such a shift is not observed in the <111>-oriented and the non-doped crystals. In addition, substantial polarization suppression occurs in the Mn-doped crystals upon FC from high temperature regardless of orientation. Based on piezoforce microscopy of the domain structure that shows suppression of domain growth following field cooling from 200 °C, we propose a mechanism for polarization suppression based on domain pinning by charged defects. The practical importance of our results lies in showing the opportunity offered by a proper choice of crystal composition and poling conditions for tuning the functional properties of PMN-PT single crystals for a specific application. This should contribute to the understanding of their properties towards advanced sensor and transducers devices. [ABSTRACT FROM AUTHOR]

To support practical infrared detector applications, pyroelectric ceramics should exhibit excellent pyroelectric performances, high depolarization temperatures, and good thermal stabilities. In this study, the pyroelectric properties, depolarization behaviors, and thermal stabilities of tetragonal 0.8Bi0.5Na0.5TiO3–0.2BaTiO3 (0.8BNT–0.2BT) ceramics are studied systematically. The samples exhibit high depolarization temperatures (∼209 °C) and excellent thermal stabilities. More importantly, they display high pyroelectric coefficients (p = 2.42 × 10−8 C cm−2 K−1), as well as high voltage responsivity (Fv = 2.68 × 10−2 m2 C−1) and specific detectivity (Fd = 1.53 × 10−5 Pa−1/2) figures of merit at room temperature and 1 kHz. The overall properties of tetragonal 0.8BNT–0.2BT ceramics indicate their potential for application in infrared detectors. [ABSTRACT FROM AUTHOR]

Micro x-ray fluorescence spectroscopy (μXRF) is a technique for local chemical analyses of materials. There are several advantages in comparison to other similar methods like energy dispersive x-ray spectroscopy in a scanning electron microscope (SEM). The main advantage is the possible abdication of an evacuated sample chamber, which offers the possibility to analyze wet and oil contaminated specimens as well as specimens with intrinsic pores in addition to conventional samples used in SEM analyses. The subject of this report is the investigation of the pyroelectric effect with regard to its application for the generation of focused x-rays and first steps to a successive usage of the generated radiation for μXRF applications. In order to answer questions concerning the energy and intensity of primary radiation and geometric parameters for a successful focusing, this paper describes several experiments and results against the background of the described aims. Different setups and measurements have been used, optimizing the experimental setups to find the basic parameters to potentially generate focal spots of the primary x-rays. Emission behavior of electrons has been visualized and characterized by using a phosphor screen positioned in front of a pyroelectric crystal. Radiation has been measured and characterized by using an energy dispersive silicon drift x-ray detector. All x-ray experiments were executed in a vacuum test rig. This allowed the optimization of the working pressure of the residual gas surrounding the crystal in an evacuated atmosphere (rarefied air). It has been shown that emitted x-ray energies are strongly influenced by the vacuum pressure. Lithiumniobate and lithiumtantalate of different geometries were used as the pyroelectric material. Different target materials and target angles have been compared to optimize the combination of the constructed x-rays source with an aperture as well as with an x-ray optic to focus the primary x-rays. A glass fiber capillary lens was used as the focusing optic. A first step to a μXRF application is shown. [ABSTRACT FROM AUTHOR]

NH4CuCl3, a well-studied antiferromagnet best known for its gapless magnetization and unusual magnetization plateaus, is shown here to exhibit magnetoelectric behavior below the antiferromagnetic transition temperature of 1.3 K. This is based on magnetic field and temperature dependent capacitance measurements made at millikelvin temperatures, along with the appearance of spontaneous polarization and electric-field reversible pyroelectric current. The possession of both long-range magnetic and dielectric order, combined with magnetoelectric coupling, renders this material a rather unique Cu-based multiferroic and serves as a unique template for the design of such materials. [ABSTRACT FROM AUTHOR]

NH4CuCl3, a well-studied antiferromagnet best known for its gapless magnetization and unusual magnetization plateaus, is shown here to exhibit magnetoelectric behavior below the antiferromagnetic transition temperature of 1.3 K. This is based on magnetic field and temperature dependent capacitance measurements made at millikelvin temperatures, along with the appearance of spontaneous polarization and electric-field reversible pyroelectric current. The possession of both long-range magnetic and dielectric order, combined with magnetoelectric coupling, renders this material a rather unique Cu-based multiferroic and serves as a unique template for the design of such materials. [ABSTRACT FROM AUTHOR]

The pyroelectric response of polycrystalline, Si-doped HfO2 layers with a thickness of 20 nm is investigated in a frequency range of 2 Hz to 20 kHz. Local Joule heating of the pyroelectric material by a deposited nickel strip is used to achieve fast thermal cycles. Over the whole frequency range, a distinct pyroelectric response is registered. A pyroelectric coefficient of −72 μC/m2K is obtained at a frequency of 10 Hz, which is in good agreement with earlier low-frequency measurements. The pyroelectric current is evaluated with respect to electric field cycling, where a successive increase is observed during wake-up. By comparing measurement results in the low- and high-frequency limit, primary and secondary pyroelectric coefficients of −53 μC/m2K and −19 μC/m2K are estimated, respectively. Si-doped HfO2 is a promising material for future energy harvesting and IR sensor applications due to environmental friendliness and CMOS compatible manufacturing. [ABSTRACT FROM AUTHOR]

In our experiments, the icing temperature of small water volumes placed on different pyroelectric single crystals (Sr x Ba 1−x Nb 2 O 6 , LiNbO 3 , and LiTaO 3 ) was determined using two measurement setups: (1) the sessile droplet and (2) ring system method. In the first method, a free-standing water droplet was exposed to several external factors in the air environment. This was found to lead to higher icing temperatures compared to the second method where the water was more isolated from external factors such as evaporation. In the second method, the material of the ring system was found to be an important factor determining the freezing temperature of the enclosed water. A recommendation for the application of both methods is given, their advantages and disadvantages depending on the purpose of measurement, and their reproducibility for practical applications. In addition to this, the correlation between pyroelectricity and icing temperature, with regard to several types of internal and external factors affecting water freezing, is also discussed in the paper. [ABSTRACT FROM AUTHOR]

Abstract: Metastable polymorphs commonly emerge when the formation of the stable analogues is inhibited by using different solvents or auxiliaries. Herein, we report that when glycine is grown in aqueous solutions in the presence of low concentrations of different co‐solvents, only alcohols and acetone, unlike water and acetic acid, are selectively incorporated in minute amounts within the bulk of the α‐polymorph. These findings demonstrate that although water binds more strongly to the growing face of the crystal, alcohols and acetone are exclusively incorporated, and thus serve as efficient inhibitors of this polymorph, leading to the precipitation of the β‐form. These solvents then create polar domains detectable by pyroelectric measurements and impedance spectroscopy. These results suggest that in the control of crystal polymorphism with co‐solvents, one should consider also the different desolvation rates in addition to the energy of binding to the growing faces of the crystal. [ABSTRACT FROM AUTHOR]

The article presents the experimental results of the investigation of the absorption spectra and nonlinear refraction of the metal-dielectric nanocomposite that contains the lithium niobate pyroelectric crystal coated with the silver nanofilms on its surface. The atomic force microscopy surface research of these crystals with and without films are also provided. The nanowidth silver films impact on optical spectra and nonlinear refraction of LiNbO3-Ag nanocomposite was analyzed depending on the sign of the side charge of the crystal, that contain nanofilms. [ABSTRACT FROM AUTHOR]

Active X-ray fluorescence Spectrometer (AXS) is designed and developed as an elemental analyzer to induce fluorescence X-rays from rock samples without radioactive sources for future lunar and planetary landing missions in Japan. Pyroelectric crystal is applied for X-ray generator because of its compact package, lightweight, low-power consumption, and radioactive source-free. As the X-ray emission intensity from Pyroelectric X-ray Generator (PXG) is not strong enough to be applied for space missions, we have been developing the PXG with an increased intensity to be used in future lunar and planetary landing missions. In future landing mission to the Moon, several putative landing sites are expected in the Procellarum KREEP Terrane and South Pole-Aitken Terrane, which are interesting for investigating lunar igneous activity and mantle composition, respectively. In this paper, the current status of development and science targets of AXS is reported and discussed. [ABSTRACT FROM AUTHOR]

The possibility of using PZT-19 ceramic in a pyroelectric x-ray generator is investigated experimentally. Measurements of the x-ray spectra showed the possibility of obtaining on a ceramic surface in vacuum potentials up to 7 kV, which is very low compared with typical similar values for pyroelectric crystals of lithium niobate and tantalate. This feature is due to the significant permittivity of the ceramic. It is shown that the main criterion for picking a ceramic for a pyroelectric x-ray generation could be the maximum value of the ratio of the pyroelectric constant to the permittivity. [ABSTRACT FROM AUTHOR]

Ferroelectric single crystals Mn-doped 0.29Pb(In 1/2 Nb 1/2 )O 3 -0.31Pb(Mg 1/3 Nb 2/3 )O 3 -0.40PbTiO 3 (Mn-PIMNT) have been grown by a modified Bridgman technique. The as-grown ternary tetragonal Mn-PIMNT (29/31/40) single crystals exhibit ultra-high Curie temperature T C of 216 °C, 110 °C higher than that of Mn-PMNT(72/28) single crystals( T d ∼ 105 °C). In addition, the permittivity ε r of tetragonal Mn-PIMNT(29/31/40) is 350 at 1 kHz, approximately less than that of Mn-PMNT(72/28)( ε r ∼ 640) in half. Moreover, as a core parameter of pyroelectric material, the figure of merits for detectivity ( F d ) for Mn-PIMNT(29/31/40) is 23.5 × 10 −5 Pa −1/2 , close to that of Mn-PMNT(72/28)( F d ∼ 28.5). Finally, outstanding Mn-PIMNT(29/31/40) based pyroelectric detectors were fabricated, of which the specific detectivity ( D *) (room temperature, 10 Hz) is up to 1.74 × 10 9 cmHz 1/2 /W for current-mode detectors, and 1.15 × 10 9 cmHz 1/2 /W for voltage-mode detectors, 3 times higher than that of commercial LiTaO 3 based detectors. All of these results make these ternary tetragonal Mn-PIMNT single crystals a promising candidate for infrared detector applications. [ABSTRACT FROM AUTHOR]

The feasibility of a LiTaO 3 pyroelectric crystal for pulsed neutron detection has been studied. The detector consists of a slice of electroded Z-cut LiTaO 3 pyroelectric crystal, and no additional neutron converter is required owing to the Li contained in the crystal. The slight temperature increase caused by neutron radiation will lead to the release of bound charges and will give rise to a pyroelectric signal. The response of it has been studied both theoretically and experimentally. Our preliminary experiment on the CFBR-II reactor suggests that the LiTaO 3 pyroelectric detector is promising for high intensity neutron – pulse measurement. [ABSTRACT FROM AUTHOR]

This study is an attempt to formulate figures of merit (FOMs) for pyroelectric energy-harvesting devices that include the material's physical properties (pyroelectric coefficient, density, and heat capacity) along with dimensions of the material (thickness and area). The figures of merit are reported for pyroelectric generators using a scaling method, and these FOMs are slightly different from existing reported FOMs, likely due to the consideration of convective heat losses during materials heating. These losses have significant importance in pyroelectric energy-harvesting applications which had not been previously considered in the existing FOMs reported in the literature. Such FOMs can be directly used for materials selection as well as for efficient device design for pyroelectric energy harvesting applications. [ABSTRACT FROM AUTHOR]

The applicability of polarized ferroelectric ceramics as a pyroelectric in a pyroelectric accelerator is shown by experiments. The spectra of X-ray radiation of energy up to tens of keV, generated by accelerated electrons, have been measured on heating and cooling of the ceramics in vacuum. It is suggested that curved layers of polarized ferroelectric ceramics be used as elements of ceramic pyroelectric accelerators. Besides, nanotubes and nanowires manufactured from ferroelectric ceramics are proposed for the use in nanometer-scale ceramic pyroelectric nanoaccelerators for future applications in nanotechnologies. [ABSTRACT FROM AUTHOR]

In this work a new approach for ice repellent coatings is presented. It was shown that the coatings cause a decrease or increase in the freezing temperature of water depending on the alignment of an external electric field. For this coating the commonly used pyroelectric polymer polyvenylidene fluoride was deposited as a thin film on glass. The samples were dip-coated and subsequently thermally-treated at 140 °C for 1 h. All samples were found to cause a reduction of the icing temperature of water on their surface in comparison to uncoated glass. On several samples an external electric field was applied during this thermal treatment. The field application was found to cause a remarkable reduction of the icing temperature where a maximum lowering of the freezing temperature of 3 K compared to uncoated glass could be achieved. The actual achieved reduction of the icing temperature was observed to depend on the polarity of the field applied during the thermal treatment. Furthermore, a repetition of the thermal treatment under oppositely directed electric fields led to a switchable freezing behavior of water according to the direction of the applied field. With an increasing number of cycles of switching of the icing property a slight training effect towards lower freezing temperatures was observed. [ABSTRACT FROM AUTHOR]

Low grade waste thermal energy is a prominent energy source for miniature devices. Present study reports experimental observations on thermal energy harvesting using pyroelectric ceramics (PbZrxTi1-xO3(PZT-5H)). Appropriate electrical circuit was connected to the pyroelectric material for harvesting thermal energy. Hot/cold air was used to generate the continuous temporal temperature gradient. The temporal temperature variation was maintained as 4oC/sec. In order to study the behaviour of pyroelectric material for energy harvesting, generated charge was stored in capacitor. The maximum energy density was found to be 187.23 μJ/cm3across 10 μF. Peak value of power output was 0.26 μW across 5MΩ and 4.7 μF. [ABSTRACT FROM AUTHOR]

A distributed electrode structure of sensitive element based on Mn-doped Pb(Mg 1/3 Nb 2/3 )O 3 -0.29PbTiO 3 single crystals for high-end pyroelectric infrared detectors has been proposed, demonstrating a notably superior pyroelectric response. Under the optimal electrode distance of 0.5 mm, the figure of merit for detectivity is up to 39.9 × 10 −5 Pa −1/2 . An ultrahigh responsivity of 864 V/W and specific detectivity of 1.49 × 10 9 cm Hz 1/2 /W at 10 Hz are observed, approximately 3.6 and 1.4 times higher, respectively, than that of the conventional faced electrode structure. The enhanced responsivity and specific detectivity of the distributed electrode structure will make PMNT based detectors with voltage mode promising in practical use of sensors. [ABSTRACT FROM AUTHOR]

Single crystal growth of lead antimony tartrate dihydrate, Pb[Sb2((+)C4H2O6)2]·2H2O, was successfully performed. The determined polar hexagonal crystal structure is isomorphous to the corresponding calcium and strontium antimony tartrates dihydrates. New results of crystal growth and the redetermination of the crystal structures of the nonlinear optical crystal Sr[Sb2((+)C4H2O6)2]·2H2O and its calcium analogue are reported, together with investigations of the thermal stability and the pyroelectric properties of these polar crystals. [ABSTRACT FROM AUTHOR]

Pyroelectric energy conversion is a novel energy process which directly transforms waste heat energy from cyclic heating into electricity via the pyroelectric effect. Application of a periodic temperature profile to pyroelectric cells is necessary to achieve temperature variation rates for generating an electrical output. The critical consideration in the periodic temperature profile is the frequency or work cycle which is related to the properties and dimensions of the air layer; radiation power and material properties, as well as the dimensions and structure of the pyroelectric cells. This article aims to optimize pyroelectric harvesters by matching all these requirements. The optimal induced charge per period increases about 157% and the efficient period band decreases about 77%, when the thickness of the PZT cell decreases from 200 µm to 50 µm, about a 75% reduction. Moreover, when using the thinner PZT cell for harvesting the pyroelectric energy it is not easy to focus on a narrow band with the efficient period. However, the optimal output voltage and stored energy per period decrease about 50% and 74%, respectively, because the electrical capacitance of the 50 µm thick pyroelectric cell is about four times greater than that of the 200 µm thick pyroelectric cell. In addition, an experiment is used to verify that the work cycle to be able to critically affect the efficiency of PZT pyroelectric harvesters. Periods in the range between 3.6 s and 12.2 s are useful for harvesting thermal cyclic energy by pyroelectricity. The optimal frequency or work cycle can be applied in the design of a rotating shutter in order to control the heated and unheated periods of the pyroelectric cells to further enhance the amount of stored energy. [ABSTRACT FROM AUTHOR]

The compounds belonging to the perovskite class often exhibit complex temperature- or pressure-induced sequences of ferroelectric or structural phase transitions. The understanding of interaction between such lattice instabilities, which are different in nature, is an important problem due to wide range of applications of perovskite-based materials. One of the common examples of such interaction is the co-existence of ferroelectricity and octahedral tilting, which is most pronounced in PbZr 1− x Ti x O 3 (PZT) solid solutions. In this work using dielectric and pyroelectric measurements we study the octahedral tilting phase transition in PZT (0.07 ≤ x ≤ 0.24), which has a pronounced dome-shaped form in the T – x phase diagram and a tricritical point at x ≈ 0.17. Based on crystallographic arguments we further suggest a phenomenological model of phase transitions in PZT capable of describing the dome-shaped form of the R3m – R3c octahedral tilting phase transition line as well as positions of the tricritical points. The implications of the obtained results for perovskites in general are discussed. [ABSTRACT FROM AUTHOR]

Pyroelectric crystals are used to produce high energy electron beams. We have derived a method to model electric potential generation on LiTaO3 crystal during heating cycle. In this method, effect of heat transfer on the potential generation is investigated by some experiments. In addition, electron emission from the crystal surface is modeled by measurements and analysis. These spectral data are used to present a dynamic equation of electric potential with respect to thickness of the crystal and variation of its temperature. The dynamic equation's results for different thicknesses are compared with measured data. As a result, to attain more energetic electrons, best thickness of the crystals could be extracted from the equation. This allows for better understanding of pyroelectric crystals and help to study about current and energy of accelerated electrons. [ABSTRACT FROM AUTHOR]

0-3 (Pb[(MnNb)(MnSb)](ZrTi)O)(PZT)/carbon black/Poly (vinylidene fluoride) (PVDF) pyroelectric composites were prepared by hot-pressing technology. The volume conductivity, specific heat capacity, dielectric, piezoelectric and pyroelectric properties of the composites with various nano carbon black powder contents were discussed. The results showed that the nano carbon black powder acted as a conductive phase which could improve the conductive of the composites, thereby enhance the electrical properties. With addition of 0.9 wt% nano carbon black powder, the composites exhibited the best pyroelectric property, which was about 1.3 times of those composites without nano carbon black powder. It is concluded that nano carbon black powder doping is an effective method to improve the pyroelectric performance of the composites, which is good candidate for the future infrared detector application. [ABSTRACT FROM AUTHOR]

The study of pyroelectric response of monocrystalline TGS cubic specimens to changes of temperature induced by linear and pulse heating of three mutually perpendicular pairs of cube sides demonstrated a complicated structure of signals. We attribute their forms to the activation of various hydrogen bonds between glycine G1, G2, and G3 molecules. In the case of pulse heating the pyroelectric signal is observed also in the paraelectric phase. [ABSTRACT FROM AUTHOR]

Pyroelectric crystals are used to produce high energy self-focused electron beams. Here, an experimental analysis in combination with simulation studies will be reported to investigate possible sources of this effect. In the experiments, the surface of crystal was divided into six separated parts and the rate of surface electric charge production was measured accordingly. A non-steady and spatially non-uniform distribution of the surface charge generation was observed, in which it tends to a uniform distribution in the course of experiment. The obtained surface electric charges from the experiments were used to simulate the electric field and potential around the crystal by COMSOL Multiphysics. It was observed that emitted electrons from the crystal surface were focused, and the non-uniformity in spatial charge is responsible for this phenomenon. [ABSTRACT FROM AUTHOR]

On the basis of an analysis of charge properties of a 'quantum well - barrier' pair, each substance of which possesses pyroelectric or piezoelectric polarization, an expression for calculating the polarization coefficients (pyroelectric coefficients, piezomodules) is obtained. This expression is analytically simple and physically evident and allows to calculate the required coefficients for multiple quantum wells with any number of the 'quantum well - barrier' pairs. Numerical estimates of the multiple quantum well parameters made for various ratios between the quantum-well and barrier thicknesses are consistent with values expected from physical consideration. [ABSTRACT FROM AUTHOR]

We developed a method to pole electro-optic (E-O) polymer thin films using pyroelectric crystals instead of external high voltage source unit. The process is based on a multi-layered dielectric stack, in which micron-thick E-O polymer films were sandwiched between millimeter thick pyroelectric crystal and borosilicate glass substrate. Through modest temperature change, very large electric fields could be spontaneously generated from pyroelectric effect of the crystals, which can deliver high effective field strength (up to 0.7 MV/cm) to the E-O polymer thin films across the glass plate. Very intriguing phenomena of significantly reduced leak through current (LTC) and improved dielectric breakdown strength of E-O polymers were observed. As a result, large Pockels coefficients of 62 pm/V at 1.31 µm can be obtained for poled E-O thin films. The good agreement between theory and experimentally measured results in the study provide important insights of electrostatics in pyroelectric systems and their effective interactions with thin film E-O polymeric materials. It also demonstrates that pyroelectric poling is a promising alternative to commonly used contact poling and corona poling that offers unique advantages of high field strength and near-zero LTC for polarizing dielectric functional materials and devices. [ABSTRACT FROM AUTHOR]

Highlights: [•] High T c and high pyroelectric coefficient are obtained by component regulatory. [•] Mn-doping contributes to depress dielectric loss to 0.0003. [•] Dielectric and pyroelectric performances depend on the number of oxygen vacancies. [•] Oxygen-annealing promotes detectivity figure of merit up to 34.1×10−5 Pa−1/2. [•] P–E loops describe domain switching with frequency of applied electric field. [ABSTRACT FROM AUTHOR]

Highlights: [•] Infrared lock-in thermography has been applied as fast and convenient non-contact method. [•] A complete thermal characterization of Cd1−x−y Zn x Mg y Se semiconductors was carried out. [•] Thermal parameters were sensitive on the fabrication process and the quality of crystals. [•] The effect of Mg/Zn molar ratio on thermal properties was analyzed and discussed. [ABSTRACT FROM AUTHOR]

Pyroelectric infrared (PIR) sensors are widely used as a presence trigger, but the analog output of PIR sensors depends on several other aspects, including the distance of the body from the PIR sensor, the direction and speed of movement, the body shape and gait. In this paper, we present an empirical study of human movement detection and identification using a set of PIR sensors. We have developed a data collection module having two pairs of PIR sensors orthogonally aligned and modified Fresnel lenses. We have placed three PIR-based modules in a hallway for monitoring people; one module on the ceiling; two modules on opposite walls facing each other. We have collected a data set from eight subjects when walking in three different conditions: two directions (back and forth), three distance intervals (close to one wall sensor, in the middle, close to the other wall sensor) and three speed levels (slow, moderate, fast). We have used two types of feature sets: a raw data set and a reduced feature set composed of amplitude and time to peaks; and passage duration extracted from each PIR sensor. We have performed classification analysis with well-known machine learning algorithms, including instance-based learning and support vector machine. Our findings show that with the raw data set captured from a single PIR sensor of each of the three modules, we could achieve more than 92% accuracy in classifying the direction and speed of movement, the distance interval and identifying subjects. We could also achieve more than 94% accuracy in classifying the direction, speed and distance and identifying subjects using the reduced feature set extracted from two pairs of PIR sensors of each of the three modules. [ABSTRACT FROM AUTHOR]

Spontaneous polarization, thermally stimulated conductivity and depolarization are comprehensively studied in the range from 4.2 to 300 K on nonstoichiometric n-type CdS crystals grown from the gas phase in an argon atmosphere at T = 1450 K. The objects of study are initial samples and samples polarized by a weak electric field at T = 4.2 K. Sample polarization results in a decrease in the conductivity σ due to restructurization of the entire energy level spectrum associated with the formation of donor-acceptor pairs. The latter processes also contribute to the temperature dependences of the spontaneous polarization and the pyroelectric effect, characterized by the formation of anomalies below 15 K and the formation of thermoelectret. The role of an uncontrollable oxygen impurity in the formation of CdS cationic conductivity above 270 K, associated with the decay of a fraction of donor-acceptor pairs, is discussed. In the temperature range from 20 to 250 K, the pyroelectric coefficient and spontaneous polarization are independent of external influences within experimental error; at T = 200 K, they are Δ P = −(6.1 ± 0.2) × 10 C/m and γ = −(4.1 ± 0.3) × 10 C/m K. [ABSTRACT FROM AUTHOR]

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Pyroelectric property of orthorhomic GdMnO3 polycrystalline samples was investigated. Two pyrocurrent peaks were observed with the sharp one near 20K and the broad one at around 120 K. The dependences of these two peaks on magnetic field, heating rate, and poling voltage were explored systematically. The sharp peak is related to the ferroelectric transition, while the behavior of the broad one corresponds to dipole reorientation. Some key pyroelectric features are proposed to separate the spin-induced ferroelectricity from other effects. This work is helpful for understanding the pyroelectric property of multiferroic materials. [ABSTRACT FROM AUTHOR]

Pyroelectric property of orthorhomic GdMnO3 polycrystalline samples was investigated. Two pyrocurrent peaks were observed with the sharp one near 20K and the broad one at around 120 K. The dependences of these two peaks on magnetic field, heating rate, and poling voltage were explored systematically. The sharp peak is related to the ferroelectric transition, while the behavior of the broad one corresponds to dipole reorientation. Some key pyroelectric features are proposed to separate the spin-induced ferroelectricity from other effects. This work is helpful for understanding the pyroelectric property of multiferroic materials. [ABSTRACT FROM AUTHOR]

We report pyroelectric emission from PbZrxTi1-xO3 (PZT) thin films on nanometer-sharp tips. The epitaxial PZT films are 30 nm thick and grown directly on single-crystal silicon tips. Pyroelectric emission occurs for heating rates of ≥50 °C/min in a 20 V/μm external field. The emission current is a maximum of 240 nA when the heating rate is 100 °C/min and the electric field strength is ≥6.7 V/μm. The emitted charge is ∼7% of that expected for a perfect thin film emitter of epitaxial PbZrxTi1-xO3. We calculate that pyroelectric emission can occur without an applied field if the heating rate exceeds 4.0 × 107 °C/min. [ABSTRACT FROM AUTHOR]

Abstract: Two cylindrical LiTaO3 crystals facing each other''s deuterated circular face were exposed to deuterium gas at an ambient pressure of a few mTorr. With a distance of about 4cm between the z+ and z− cut crystal faces, neutrons were produced via the 2H(d,n)3He fusion reaction upon the heating and cooling of the crystals. The 2.5MeV neutrons were detected with organic liquid scintillation detectors equipped with neutron-gamma pulse-shape discrimination electronics to reject pulses generated by the intense X-ray flux. During the cooling phase of naked crystals, deuterium ion-beam (D2 +) energies of up to 400keV were obtained as deduced from the associated electron bremsstrahlung end-point energy. The highest electron-beam energy observed during the heating phase was 360keV. With a layer of deuterated polyethylene evaporated on the front face of the crystals, the maximal energies were about 10% lower. In contrast to earlier studies, an electric-field enhancing nano-tip was not employed. Neutron yields up to 500 per thermal cycle were observed, resulting in a total neutron production yield of about 1.6×104 neutrons per thermal cycle. Our approach has the potential of being substantially improved by reducing the frequency of the discharges we are currently experiencing with our geometry, which was not designed for the unprecedented high potentials produced in the presentwork. [Copyright &y& Elsevier]

The production of pyroelectric type X-ray generators has a long term background. In case of using X-ray generators containing two pyroelectric crystals, some parameters have not been practically measured yet. This article aims to calculate such parameters by means of Geant4 Mont Carlo codes. The obtained edge energy of initial electrons was 3 keV at a constant pressure of 1mTorr and electric field of 250 kV/cm. The amplification coefficient production of electrons was increased reaching to a constant value of 2.7. The observed mean energy of produced gas ions was approximately 39 eV, equivalent to 5.7% of the emitted electrons. The efficiency of the generated X-ray was about 63% and did not show a considerable change as the energy of initial electrons increased. [ABSTRACT FROM AUTHOR]

Abstract: Thin lithium tantalate pyroelectric crystals in a multi-stage pulser were heated by quartz lamps during their charging phase to generate high voltage pulses. The charging voltage was determined empirically based on the measured breakdown voltage in air and verified by the induced breakdown voltage of an external high voltage power supply. A four-stage pyroelectric crystal device generated pulse discharges of up to 86kV using both quartz lamps (radiative) and thermoelectric (conductive) heating. Approximately 50mJ of electrical energy was harvested from the crystals when radiatively heated in air, and up to 720mJ was produced when the crystals were submerged in a dielectric fluid. It is anticipated that joule-level pulse discharges could be obtained by employing additional stages and optimizing the heating configuration. [Copyright &y& Elsevier]

We report a portable rare-earth element analyzer with a palm-top size chamber including the electron source of a pyroelectric crystal and the sample stage utilizing cathodoluminescence (CL) phenomenon. The portable rare-earth element analyzer utilizing CL phenomenon is the smallest reported so far. The portable rare-earth element analyzer detected the rare-earth elements Dy, Tb, Er, and Sm of ppm order in zircon, which were not detected by scanning electron microscopy-energy dispersive X-ray spectroscopy analysis. We also performed an elemental mapping of rare-earth elements by capturing a CL image using CCD camera. [ABSTRACT FROM AUTHOR]

X-ray fluorescence (XRF) spectroscopy is a frequently used technique for the chemical analysis of materials due to several advantages such as its almost nondestructive character. Subjects of this report are investigations of the pyroelectric effect with regard to its application for the generation and acceleration of x-rays and a successive usage of radiation for XRF in materials science. In order to answer questions concerning the intensity of primary radiation and of fluorescence radiation, this paper contains several experimental investigations. Different setups and measurements have been used to increase intensity. Emission behavior of electrons has been characterized using measurements of electron current in a target positioned in front of a pyroelectric crystal as a function of the temperature of the crystal and time. Radiation has been coupled out, and its dose equivalent rate has been measured. This allowed the optimization of the working pressure of the residual gas surrounding the crystal in an evacuated atmosphere (rarefied air). It has been shown that a vacuum pressure of approximately 5 × 10−1 Pa allows the generation of radiation with high intensities. Different target materials have been compared due to the intensity of excited fluorescence radiation of a sample by using an energy dispersive radiation detector. A qualitative and quantitative analysis of elements contained in the sample has been proven to be feasible. A possible application of the radiation for imaging has been investigated. [ABSTRACT FROM AUTHOR]

Using a heated pyroelectric crystal, an atmospheric pressure gas discharge was generated through the input of heat. When put through a change in temperature, the polarization of a pyroelectric can change significantly, creating a substantial electric potential at its surface. When configured with a grounded sharp counter electrode, a large inhomogeneous electric field forms in the interstitial gas to initiate a corona-like discharge. Under constant heating conditions, gaseous ions drifting to the pyroelectric accumulate and screen the electric field, extinguishing the discharge. By thermally cycling the pyroelectric, negative and positive discharges are generated during heating and cooling, respectively, with peak currents on the order of 80 nA. Time-integrated visualization confirmed the generation of both a corona-like discharge and a surface discharge on the pyroelectric. Parametric studies identified that thermal cycling conditions significantly influence discharge formation for this new atmospheric pressure discharge approach. [ABSTRACT FROM AUTHOR]

We report a method to focus the electron beam generated using a pyroelectric crystal. An electron beam with a spot size of 100 μm was achieved by applying an electrical field to an electroconductive needle tip set on a pyroelectric crystal. When the focused electron beam bombarded a sample, characteristic X-rays of the sample were only detected due to the production of an electric field between the needle tip and the sample. [ABSTRACT FROM AUTHOR]