Temperature Dependence Of Piezoelectric Constants Research Articles

CaxSr0.3−xBa0.7Nb2O6 lead-free pyroelectric ceramics with high depoling temperature

CaxSr0.3−xBa0.7Nb2O6 [CSBN (x), x = 0.00, 0.10, 0.20, and 0.30] lead-free ceramics were fabricated by traditional solid-state reaction technique. The morphology, structure, dielectric, ferroelectric and pyroelectric properties of CSBN (x) ceramics were systematically studied. The thermal depoling behaviors were evaluated through measurements of temperature dependence of piezoelectric constant (d33). All CSBN (x) ceramics exhibited obvious diffuse phase transitions and maximum dielectric constant (εm) increased monotonically with x. The ferroelectric and pyroelectric properties of CSBN (x) have been enhanced remarkably due to Ca addition. The remnant polarization (Pr) and pyroelectric coefficient (p) of CSBN (0.30) samples reached 4.95 μC/cm2 and 1.30 × 10−8C/cm2K which roughly tripled and doubled pure SBN. What's more, CSBN (0.20) samples achieved rather high pyroelectric figure of merit of voltage (Fv = 0.0203 m2/C) which is superior to many other lead-free materials and pyroelectric figure of merit of detectivity (FD) for CSBN (0.20) and CSBN (0.30) samples both soared to 0.61 × 10−5Pa−1/2. The most inspiring part is the depoling temperature and Curie temperature noticeably shifted to higher temperature region owing to Ca addition. These results unveil the potential of CSBN (x) ceramics for infrared detector applications.

Frequency, electric field and temperature dependence of piezoelectric constant of Pb(Zr,Ti)O3 based ceramics under high electric field

Frequency, electric field and temperature dependence of piezoelectric constants d31 were measured under strong electric fields by a static method based on a linear response theory for Pb(Zr0.5Ti0.5)O3 (PZT) and Pb(Zr0.5Ti0.5)O3+0.3wt% MnO2 (Mn-PZT) ceramics. The result shows that the piezoelectric relaxation exists around 0.1Hz for the PZT and tens of heltz for the Mn-PZT at a room temperature. The d31 of the PZT decreases about 35% from 0.01Hz to 400Hz under an electric field of 20kV/cm and decreases about 20% from electric fields of 20kV/cm to 0kV/cm at 400Hz. It is confirmed that the d31 at 400Hz extrapolated to 0kV/cm is almost the same as that measured by the resonance-antiresonance method for the PZT. Temperature dependence of the d31 was also discussed.

Temperature Dependence of Strain Induced by Electric Field in Piezoelectric Ceramics

The temperature dependence of piezoelectric constant (d31) and the strain characteristics of the (Pb0.845Ba0.105Sr0.05) ((ZrxTi1-x)0.95Sn0.045Nb0.005)O3 series (x=0.49, 0.52, 0.55), in which the grain size was controlled by hot-pressing (HP), were investigated between -196 and 90°C. The piezoelectric constant (d31) was measured using an impedance analyzer (YHP4192A). The strain characteristics were measured by applying DC electric field (1.0kV/mm) and the durability under repetitious DC electric field (1.0kV/mm, 1Hz). The results showed that the piezoelectric constant (d31) and the actually found strain (δ) under DC electric field increase with increasing temperature. Between -196 and 90°C, the actually found strain (δ) was larger than calculated value (δcal), obtained by multiplying the d31 with DC electric field. This difference (δ-δcal) was caused by the strain (δp) of domainial reorientation alone the intensity of electric field. It is found that the δp was nearly zero at -196°C (liquid nitrogen temperature), and increases with increasing temperature. Furthermore, it was clarified that the temperature dependence of δp varied with the composition and grain size. It is shown that the temperature dependence of δp is related to that of the binding force of domain (σb). In the durability test between -196 to 90°C, the δ became small after the test. The change of δ increased with increasing temperature. It is found that the decrease of δp led to that of δ. We found that the change of δp is dependent on the composition and grain size.

Piezoelectric Relaxations in Collagen Gelatin Systems

Films consisting of three joined layers of gelatin, oriented collagen, and gelatin were prepared. The temperature dependence of piezoelectric constants (d=d′–id″) and e=e′–ie″ was determined at 10 Hz for the combined films with different hydrations. At a moisture content above 30 wt %, d′ and e′ decreased with increasing temperature just above −100°C, and their signs reversed around −30°C, and approached zero around room temperature. The temperature dependence of the piezoelectric current induced by static stress was also determined for a film with a moisture content of about 33 wt%. The sign reversal of the decaying current was observed at intermediate temperatures in accord with the sign reversal of d′ in a.c. measurements. The theoretical explanation for this was given on the basis of the Maxwell—Wagner type dielectric relaxation in a two phase system and the decay of piezoelectric polarization in collagen layer. The same explanation may be applied for the temperature dependence of the piezoelectric constant of bone, which consists of collagen fibers and hydroxyapatite.

Piezoelectric and Elastic Properties of LiTaO3: Temperature Characteristics

Piezoelectric and elastic constants of lithium tantalate single crystal were measured from room temperature up to the Curie point (630°C). These constants were obtained by measuring resonant and antiresonant frequencies of bars and plates with various orientations. Temperature dependence of piezoelectric constants was discussed on the basis of the electrostrictive effect in the paraelectric phase biased by spontaneous polarization. Anomalous behavior of d33 and d31 was well explained by the dielectric anomaly of ε33T.