Temperature Dependence Of Pyroelectric Coefficient Research Articles

Pyroelectric performance, dielectric response and conductive mechanism of BCHT lead-free piezoelectric ceramics via powder injection molding

Lead zirconate titanate (PZT) ceramics exhibit excellent piezoelectric performance, which expands piezoelectric applications scope. However, the usage of toxic PbO causes serious harm to humans and ecological environment. Lead-free environment friendly (Ba0.85Ca0.15)(Hf0.10Ti0.90)O3 (BCHT) ceramics exhibit enhanced electrical properties when prepared via the powder injection molding process, relating to the polymorphic ferroelectric phases coexistence. Excellent pyroelectric properties are obtained in the BCHT ceramics, where pyroelectric anomaly and peak appear around 45 °C and 95 °C in temperature dependent pyroelectric coefficient and figures of merit, respectively, which can be attributed to the polymorphic phase transition and ferroelectric phase transition. Abnormal drastic change and large peak values of pyroelectric properties around the Curie temperature TC make the BCHT ceramics promising application for critical temperature detection. The dielectric response contribution was analyzed by Rayleigh formula fitting, where the reversible contribution takes major role at low temperatures and the irreversible contribution takes main effect at high temperatures. The conduction activation energy is 0.71 eV for the BCHT ceramics, which correlates with the increased oxygen vacancies induced by cations evaporation during sintering.

Electrocaloric effect and pyroelectric performance in (K,Na)NbO3‐based lead‐free ceramics

AbstractThe issue of how to achieve an electrocaloric effect (ECE) and pyroelectric effect in a material simultaneously remains to be a challenge for developing practical solid‐state cooling devices and RF‐detectors. Here, we structure a polymorphic phase transition (PPT) region by doping modification in KNN‐based ceramics, which are developed to achieve the ECE. The direct measured ECE and pyroelectric properties are investigated in lead‐free (1‐x)K0.5Na0.5NbO3‐xBi0.5Na0.5ZrO3 (KNN‐xBNZ) ceramics. The adiabatic temperature change (∆T) of 0.22 K at 100°C, 0.14 K at 70°C and 0.16 K at 30°C can be obtained under an electric field of 35 kV cm–1 for x = 0.03, 0.04 and 0.05, respectively. In addition, the temperature dependence of pyroelectric coefficient (p) is established for all compositions via the Byer‐Roundy method. A large p of 454.46 × 10–4 C m–2 K–1 is detected at Curie temperature (TC) in the ceramics with x = 0.03. Achieving electrocaloric effect and pyroelectric performance simultaneously may shed light and provide a feasible design scheme for developing practically useful electrocaloric and pyroelectric materials.

Demonstration of a pyroelectric wireless temperature sensor

Energy generation systems operating at high temperatures are becoming increasing dependent on real-time measurements to enhance the overall performance. Since most sensors in energy systems are exposed to high temperature, high pressure, or corrosive environments where wiring is not desirable, harsh environment temperature sensing is preferred to be measured wirelessly. In this study, Pb(Zr0.52Ti0.48)O3 (PZT) pyroelectric ceramic was used to develop a wireless temperature sensor. An electromagnet was built with a set number of loops of wire, length, and radius. A PZT ceramic exposed to a heating source to induce a rate of temperature change with time. Generated current from the PZT due to experiencing a rate of temperature change with time was then supplied to the electromagnet to generate a magnetic field. The magnetic field was measured remotely with a milligaussmeter. The electromagnet was first characterized by measuring the magnetic field at different distances from the edge of the electromagnet along its axis. The milligaussmeter was able to detect the magnetic field generated by PZT pyroelectric ceramics at the specified distances from the electromagnet. A PZT sensor with a thickness of 0.1 cm was tested for use in a wireless temperature measurement configuration. Due to the non-linear pyroelectric response of PZT, the temperature dependent pyroelectric coefficient of PZT was also measured with a dynamic pyroelectric measurement technique in the temperature range from room temperature to 122 °C. The temperature dependent pyroelectric coefficient of PZT was found to increase from −40 × 10−5 C m−2 °C to −71.84 × 10−5 C m−2 °C. The PZT sensor was then tested for wireless temperature measurement applications at 100 °C, 150 °C, and 200 °C, and showed a maximum 10% deviation from baseline measurements.

Characterization of the pyroelectric coefficient of a high-temperature sensor

Temperature is one of the most important thermodynamic properties measured and controlled in energy generation systems. To operate the energy system at optimum operating conditions for lower emission and higher efficiency, it is important to measure real-time temperatures. Furthermore, temperature sensing in intense environments is necessary since most sensors in energy systems get exposed to elevated temperatures, corrosive environments, and elevated pressures. One of the solutions for developing harsh environment sensors is to use ceramic materials, especially functional ceramics such as pyroelectrics. Pyroelectric ceramics could be used to develop active sensors for both temperature and pressure due to their capabilities in coupling energy among mechanical, thermal, and electrical domains. In this study, Lithium niobate (LiNbO3) pyroelectric ceramic material was used to develop a temperature sensor for high-temperature applications. LiNbO3 has high Curie temperature (1210°C) compared to other pyroelectric ceramic materials. A high Curie temperature material is important since the polarization properties of the material break down above the Curie temperature. Hence, the use of a material with a higher Curie temperature, such as LiNbO3, makes it promising to be used as a sensing material for high-temperature applications. A study was performed to actively measure the temperature up to 500°C using a pyroelectric ceramic lithium niobate (LiNbO3) as a sensor material. Due to the non-linear pyroelectric response of LiNbO3, the temperature-dependent pyroelectric coefficient of LiNbO3 was measured with a dynamic pyroelectric coefficient technique in temperature ranges up to 500°C. Temperature-dependent pyroelectric coefficient of LiNbO3 was found to increase from −0.5 × 10−5 to −3.70 × 10−5 C/m2°C from room temperature to 500°C. The LiNbO3 sensor was then tested for higher temperature sensing at 220°C, 280°C, 410°C, and 500°C and has shown 4.31%, 2.1%, 0.4%, and 0.6% deviation, respectively, compared with thermocouple measurements.

Enhanced electrocaloric, pyroelectric and energy storage performance of BaCexTi1−xO3 ceramics

BaCexTi1−xO3 (BCT) ceramics with compositions x=0, 0.1, 0.12 and 0.15 were synthesized using conventional solid state reaction route. Systematic exploration of enhancing electrocaloric effect (ECE) in BaTiO3 by rare earth dopant Ce is presented. BaCe0.12Ti0.88O3 exhibited an electrocaloric strength of ∼0.35Km/MV at 351K, which caters the need for a series of high-level ECE material. Further, the temperature dependence of pyroelectric coefficient is established for all compositions. The pyroelectric figure of merits (FOMs) for current responsivity (Fi), voltage responsivity (Fv), detectivity (Fd) and energy harvesting (Fe and Fe*) are calculated and the results reveal that x=0.1 could be a technologically superior candidate for pyroelectric devices. Further, BaCe0.15Ti0.85O3 exhibited highest electrical energy storage performance of 115kJ/m3 compared with 71kJ/m3 in BaTiO3. Our findings in this work may provide a better understanding for developing high ECE materials combined with pyroelectric and energy storage performance of Ce substituted BaTiO3 ceramics.

The pyroelectric coefficient of free standing GaN grown by HVPE

The present study reports on the temperature dependent pyroelectric coefficient of free-standing and strain-free gallium nitride (GaN) grown by hydride vapor phase epitaxy (HVPE). The Sharp-Garn method is applied to extract the pyroelectric coefficient from the electrical current response of the crystals subjected to a sinusoidal temperature excitation in a range of 0 °C to 160 °C. To avoid compensation of the pyroelectric response by an internal conductivity, insulating GaN crystals were used by applying C, Mn, and Fe doping during HVPE growth. The different pyroelectric coefficients observed at room temperature due to the doping correlate well with the change of the lattice parameter c. The obtained data are compared to previously published theoretical and experimental values of thin film GaN and discussed in terms of a strained lattice.

Dielectric response and pyroelectric properties of lead-free ferroelectric Ba3(VO4)2

The current paper presents results of dielectric response, pyroelectric behavior and conductivity study of lead-free ferroelectric barium orthovanadate ( Ba 3( VO 4)2 or Ba 3 V 2 O 8) ceramic, for a wide range of temperature and frequency. An X-ray diffraction study suggests the formation of a single-phase compound in trigonal crystal system. The SEM micrograph of gold-coated pellet sample shows well-defined and homogeneous morphology. Detailed studies of dielectric parameters (εr and tan δ) of the compound as a function of temperature and frequency reveal their independence over a wide range of temperature and frequency. The nature of Polarization versus electric field (P–E) hysteresis loop of Ba 3 V 2 O 8 at room temperature suggests its ferroelectric nature. The temperature dependence of pyroelectric coefficient and figure of merits of the sample support its dielectric response. The nature of variation of dc conductivity with temperature confirms the Arrhenius and negative temperature coefficient of resistance (NTCR) behavior of the material.

Pyroelectric properties and conduction mechanism in solution grown glycine sodium nitrate single crystal

Nonlinear optical “glycine sodium nitrate” transparent single crystals were grown from aqueous solution by the solvent evaporation technique. The ferroelectric transition temperature was determined by dielectric measurement for GSN crystal. Temperature dependent pyroelectric coefficient and figure of merit were measured. The conduction mechanism of GSN crystal has been discussed. The lnσ−E1/2 characteristic in the high-field region supports dominating the Poole–Frenkel conduction while in the low field region; there are possibility of both Richardson–Schottky and Poole–Frenkel conduction mechanism. The activation energy of GSN crystal was found to be 0.58eV. A low value of dielectric constant and good value of the figure of merit suggest the GSN crystal more promising for IR sensing applications. Hardness value shows the stability of GSN crystal.

Microstructure, dielectric and pyroelectric properties of CaCu3Ti4O12 ceramics fabricated by tape-casting method

CaCu3Ti4O12 (CCTO) ceramics were prepared by tape-casting method. All the ceramics exhibited body-centered cubic structure. A homogeneous microstructure with clear grain boundaries was obtained by tuning the sintering temperature. The dielectric properties of CCTO were investigated in a temperature range of −100 to +300°C. A relaxation has been observed in the frequency range higher than 100kHz, the activation energy was found to be 0.07eV, close to that of the activation energy for dc conductivity (0.08eV) at low temperatures. It suggests that the polarons induced by oxygen vacancies are responsible for the conduction and relaxation process. The high-temperature dependence of the dc conductivity associated with oxygen vacancies. Also, the hysteresis loop and pyroelectric properties have been measured and the incidence of the pyroelectric effect associated with the temperature dependence of pyroelectric coefficient implies that CCTO has a vast potential in the field of high-temperature pyroelectric thermal detectors.

Structure and electric properties of sol–gel derived CaCu 3Ti 4O 12 ceramics as a pyroelectric sensor

A network microstructure with large grains isolated from one another by the regions constituted with the agglomerated fine grains of CCTO ceramics fabricated by sol–gel processing has been investigated. The temperature dependence of dielectric properties associated with the contribution of grain below 90 °C, grain boundary in the temperature range of 90–250 °C, and electrode interface above 250 °C has been demonstrated under 10 kHz from room temperature to 400 °C and the presence of dielectric diffusion behavior above room temperature is clear. Also, the pyroelectric properties have been measured up to 250 °C so as to eliminate the effect of electrode interface and the incidence of the pyroelectric effect associated with the temperature dependence of pyroelectric coefficient implies that CCTO has a vast potential in the field of high-temperature pyroelectric sensing without induced applied bias.

Pyroelectric properties of KTiOAsO 4 single crystals in the 4.2–300 K temperature range

The temperature dependence of the pyroelectric coefficient, γ s( T), of KTA (KTiOAsO 4) single crystals grown by the top-seeded solution method self-fluxes has been studied in the 4.2–300 K temperature range. A novel approach to the pyroelectric measurement has allowed to take into account both the superionic conductivity of the crystal and the resistivity drop associated with thermal release of charge carriers from traps related to trace impurities. The γ s( T) behavior in the 4.2–200 K temperature range is found to be similar to those of the isomorphic crystals belonging to the KTP (KTiOPO 4) family of crystals. The experimental results show that at the temperature of 200 K the true value of the KTA pyroelectric coefficient equals −(3.5±0.3)×10 −5 C/m 2 K. Two anomalies in the temperature dependence of the KTA pyroelectric coefficient have been revealed above 200 K, and they are discussed in terms of the superionic conductivity and structural changes associated with the temperature increase and isomorphic ion substitutions.

Dielectric and Pyroelectric Properties of (Pb0.50Sr0.50)TiO3 Ceramics

Lead strontium titanate (Pb0.50Sr0.50) TiO3 (PST) ceramics are prepared by the traditional ceramic processing. The dielectric constants and dielectric loss have been investigated in a temperature range from 25°C to 300°C. The maximum dielectric constants for unpoled and poled samples are 9924 and 9683, respectively. The temperatures of phase transition for unpoled and poled samples are observed at 153°C and 157°C, respectively. The phase-transition temperatures for unpoled and poled samples are not equal, which results from the polarization state of the domains. The remnant polarization and the coercive electric field are 18μC/cm2 and 6kV/cm, respectively, from polarization-electric field (P – E) hysteresis loop. The temperature dependence of pyroelectric coefficients of the PST ceramics is measured by a dynamic technique. The dielectric constant and loss tan δ of the poled PST ceramics are 813 and 0.010, respectively. The pyroelectric coefficients and figure of merit are 294μC/cm2K and 13.6 × 10-6 Pa-0.5, respectively, at room temperature 25°C and frequency 100Hz.

Dielectric and Pyroelectric Properties of Compositionally Graded Pb(Zr1-xTix)O3 Thin Films Prepared by Sol-gel Process

Compositionally graded ferroelectric lead zirconate titanate Pb(Zr1-xTix)O3 (PZT) thin films were grown on Pt/Ti/SiO2/Si substrates by using a sol-gel process. The final structure consists of six layers, up-graded graded films starting from PbZrO3 on the Pt electrode to the top PZT(50) layer, it consists of no Ti, 10%Ti, 20%Ti, 30%Ti, 40%Ti, and 50%Ti respectively. Whereas films with opposite gradient are called down-graded graded films. Structure and dielectric properties of the graded films was investigated by X-ray diffraction, Auger electron spectroscopy and by impedance analysis. The up-graded and down-graded PZT films annealed at 600C, exhibited the remanent polarization values of 18.0 and 24.2 C/cm2, respectively. The typical small signal dielectric constants and loss tan at a frequency of 100 Hz were 523 and 0.018, 544, and 0.020, respectively, for up-graded and down-graded PZT thin films. The temperature dependence of pyroelectric coefficients of the graded PZT films was measured by a dynamic technique. From 20C to 82C, the pyroelectric coefficients of the up-graded and down-graded PZT films up to 374 and 407 C/m2K, respectively.

Relaxor Behavior of Ge-Doped TlInS2

The dielectric and pyroelectric properties of Ge-doped (0.1 mol %) TlInS2 crystals are studied. The results demonstrate that TlInS2 is a ferroelectric relaxor. The experimental data are used to evaluate, using the Vogel–Fulcher relation, the activation energy (0.045 eV), preexponential factor (f0 = 2 × 1013 Hz), and the dipole-freezing temperature (TF = 142 K) and to determine the temperature range of the stable relaxor (nanodomain) state and the temperature of the transition to the ferroelectric (macrodomain) state, accompanied by an anomaly in the temperature-dependent pyroelectric coefficient.

Screening of Ferroelectric Polarization and Stability of Poled State in Sn 2 P 2 S 6 /Epoxy Composites

Long time aging effect for hydrostatic piezoelectric sensitivity g h and dielectric susceptibility of 0-3 type Sn 2 P 2 S 6 /epoxy composites is studied. The increase of g h coefficient with time after poling is found to be accompanied by stabilization of poled state due to screening of ferroelectric polarization in the crystalline particles. The nature of the internal electric fields stabilizing poled state in composites is discussed. The temperature dependence of pyroelectric coefficient of the composites with various Sn 2 P 2 S 6 volume fraction have been measured.

Preparation of 0.92PbZrO3–0.03PbTiO3–0.05Pb(Zn1/3Nb2/3)O3 Pyroelectric Thick Films by Screen Printing

Pyroelectric thick films of 0.92PbZrO3–0.03PbTiO3–0.05Pb(Zn1/3Nb2/3)O3 were prepared by a screen printing method on ceramic substrates using platinum bottom electrodes. A phase transition between two rhombohedral ferroelectric phases was observed for the poled thick film through the measurement of the temperature dependence of pyroelectric coefficient. The effects of the firing temperature and the types of ceramic substrates were examined. These pyroelectric thick films are very promising for use in the fabrication of highly sensitive infrared array detectors.

Pyroelectric properties of valine doped TGS single crystals

Abstract TGS was grown by a slow cooling technique adding several kinds of dopants (10 and 20 mole% alanine, 10% alanine + LiVO3, 10% and 20% valine) to an aqueous solution. The temperature dependent pyroelectric coefficient, p and the spontaneous polarization, Ps, of doped-TGS crystals were measured to study the transition temperature, Pmax and room temperature pyroelectric coefficient depending on the dopants and to calculate the figure of merit, (p/K), (K is a dielectric constant). Furthermore, several pieces were selected to investigate the positional inhomogeneities of the same sample. Moderate figure of merit (p/K) was obtained in valine doped TGS because of low temperature dielectric relaxation around −10°C, although valine doped TGS has a three times higher pyroelectric coefficient (p = 1.671μC/cm2K) at transition temperature (Tc) than that of alanine doped TGS.

Pyroelectric, pressureelectric and optical properties of potassium pentaborate tetrahydrate crystals

Abstract Results of studies of pyroelectric properties, the influence of hydrostatic pressure on spontaneous polarization, electrooptic effect and spontaneous birefringence of potassium pentaborate tetrahydrate crystals are presented. It is shown that potassium pentaborate crystals are linear pyroelectric with no phase transitions in temperature of 4.2–430 K. Obtained temperature dependence of pyroelectric coefficient has been described with the help of Einstein and Debye functions.

Chiral smectic side-chain copolymers—2. Pyroelectric effect and spontaneous polarization

Temperature dependences of pyroelectric coefficient, spontaneous polarization and relaxation time have been measured for a series of ferroelectric liquid crystalline copolymers.

Pyroelectric and dielectric properties of modified lead titanate ceramics

Abstract The temperature dependence of pyroelectric coefficient P, relative dielectric constant ε r and dielectric losses tan δ of modified lead titanate ceramics (Pb, Ca) [(Co1/2W1/2)Ti]O3 with addition of NiO and MnO2 was investigated in the 80–345 K temperature range. Frequency dependence of εr and tan δ in low frequency range was studied too. Pyroelectric coefficient P at 80 K is approximately equal to 1.10−4 C.m−2 K−1. The addition of NiO acts as a softener, whereas MnO2 decreases εr and tan δ and stabilizes the characteristics of the ceramics.