Piezoelectric constant temperature dependence in strained [111]-oriented zinc-blende MQW-SOAs

Here,we present a study of the effective piezoelectric constant(e_(14_(e)))temperature dependence in strained[111]-oriented zinc-blende quantum wells(QWs)embedded within a semiconductor optical amplifier(SOA).We determined e_(14_(e)) using a method that was insensitive to the segregation phenomenon and to the temperature dependence of the bandgap energy,which required neither fitting parameters nor temperature-dependent expressions for energy and out-of-plane effective masses of electrons and heavy holes.An e_(14_(e))=−0.0534±0.0040 C·m^(−2) at 23°C was obtained for an SOA with 1.2 nm[111]-oriented strained In0.687Ga0.313As/In0.807Ga0.193As0.304P0.696 QWs.Unlike previously published research,where e_(14_(e)) magnitude increased as temperature rised,we extracted an e_(14_(e)) magnitude that decreased as temperature increased.

Excellent piezoelectric constant and thermal stability in BiScO_(3)-PbTiO_(3) piezoelectric ceramics via domain engineering

The application of piezoelectric ceramics at high temperature is limited because they can't have both high piezoelectric coefficient and high Curie temperature.While,BiScO_(3)-PbTiO_(3)-based piezoelectric ceramics possessing high Curie temperature and piezoelectric properties simultaneously have drawn increasing attention due to their potential applications at high temperature.Here,we reported a novel compositional design of(1-x)[0.36BiScO_(3)-0.64PbTiO_(3)]-xBi(Sn_(1/3)Nb_(2/3))O_(3)(abbreviated as BS-PT-xBSN).BS-PT-xBSN ceramic samples were synthesized by conventional solid state reaction method.According to the ternary phase diagram of BS-PT-xBSN ceramics brought up in this work,the morphotropic phase boundaries(MPB)were confirmed,which is located in the vicinity of x¼0.02.It canbe identified that the x=0.02 sample near MPB has the optimal electric performance which are giant piezoelectric coefficient(d_(33)-450 pC/N,higher 18%than undoped samples)and high Curie temperature(T_(c)-368℃)as well as large remant polarization(P_(r)46.6 m C/cm^(2)).In addition,the variation of P_(r) is 3% in the temperature range of 30-180℃ and the depolarization temperature of x=0.02 ceramics is about 280℃.Structural analysis such as in-situ PFM and TEM confirms that giant piezoelectricity and depolarization temperature are attributed to the appearance of nano-domain and complexity of domains as well as the stable domain configuration.This work not only reveal the high potential of BS-PT-xBSN for high-temperature piezo-electric applications but also open up a feasible approach to design new high-temperature piezoelectric ceramics.

Determination of elastic,piezoelectric,and dielectric constants of an R:BaTiO_3 single crystal by Brillouin scattering

From the sound velocity measured using the Brillouin scattering technique, the elastic, piezoelectric, and dielectric constants of a high-quality monodomain tetragonal Rh：BaTiO3 single crystal are determined at room temperature. The elastic constants are in fairly good agreement with those of the BaTiO3 single crystal, measured previously by Brillouin scattering and the low-frequency equivalent circuit methods. However, their electromeehanical properties are significantly different. Based on the sound propagation equations and these results, the directional dependence of the compressional modulus and the shear modulus of Rh：BaTiO3 in the （010） plane is investigated. Some properties of sound propagation and electromechanical coupling in the crystal are discussed.

Influence of Particle Size on Piezoelectricity of Piezo-composites

Serial material model （Dilute model）and Limited Units （LU）method were employed to analyze the performance of binary piezo-composite system.The reckoned electric potential deployments illustrated difference while the particles were different.Their piezoelectricities were also calculated according to the model,and furthermore comparation suggested that small particles living in the tolerance improve the piezoelectricity of piezo-composite.Experiments coinciding with analyses were processed simultaneously. Ceramics were milled for different time in order to control the concentration of particle size.The results showed that the filled particles enhanced the piezoelectricity of binary piezo-composite system efficiently whereas too many chips deteriorated the performance of piezo-composites.

Preparation and piezoelectric properties of potassium sodium niobate glass ceramics

This paper describes the preparation of a piezoelectric glass ceramic material from potassium sodium niobate （Ko.sNa0.sNbO3; KNN） using a novel melting method. The effects of the subsequent heat-treatment on the optical, thermal, electrical, and mechanical properties of the material are carefully examined, and its crystal structure and surface morphol- ogy are characterized respectively by x-ray diffraction and scanning electron microscopy. This new material has a much higher piezoelectric coefficient （163 pC.N-1） than traditional piezoelectric ceramics （131 pC.N-1 ）. On this basis therefore, a strategy for the future study and development of lead-free KNN-based piezoelectric glass ceramics is proposed.

STUDY ON STRUCTURE AND PROPERTIES OF PMMN PIEZOELECTRIC CERAMICS

Piezoelectric ceramics based on PZT ceramics were prepared in solid state reaction with mixture of PbO, TiO2 and ZrO2, etc. XRD and SEM were used to confirm that the main phase in the material is tetragonal P4mm symmetry. Samples sintered are of high density. Measurement on polarized products indicate that dielectric constant, piezoelectric constant, electromechanic coupling factor and mechanical quality factor are epsilon(r)=2015, d33=578.06X10(12)C/N, K-33=0.81 and Q(m)=543.8,,respectively.

Bone-inducing Activity of Biological Piezoelectric Ceramic

To simulate the piezoelectric effect of nature bone, two kinds of biological piezoelectric composite ceramics consisted of hydroxyapatite （ HA ） and lithium sodium potassium niobate （LNK） ceramic of which the ratio of HA/LNK was 1 ： 10 and 5 ： 5（ wt/ wt ） were prepared. Their piezoelectric property and growth of apatite crystal in the ceramics surface were investigated. With the increase of LNK amount, piezoelectric activity increased correspondingly. By immersing the poled piezoelectric ceramics in simulated body fluid （SBF） at 36.5 ℃ for 7, 14, and 21 days, apatite crystal was formed on negatively charged surfaces. After 21 days immersion in SBF, the thickest apatite crystal on the negatively charged surfaces increased to 3. 337 μn. The hotel biological piezoelectric ceramics show an excellent piezoelectric property and superior potential bioactivity.

Synthesis and Piezoelectric Properties of Lead-free (Bi_(0.5)Na_ (0.5))_ 1-x(Ba_aSr_b)_xTiO_3 Ceramics

A new group of lead-free piezoelectric ceramics,（Bi0.5 Na0.5）1-x（BaaSrb）xTiO3（abbreviated as BNBST[100x-100a/100b],0〈x〈1,a＋b=1）,was synthesized.The ceramics were prepared by conventional ceramic sintering technique,and the ceramics with density of 95% of the theoretical one can be sintered without the atmosphere control during the sintering process.The results of the X-ray diffraction（XRD） data show that the ceramics possess a single perovskite phase.The measurements of dielectric and piezoelectric properties reveal that the ceramics provide relatively high piezoelectric charge constant d33 and high planar electromechanical coupling factor kp.For the BNBST6-95/5 ceramics,d33 is equal to 170pC/N,and kp is equal to 32.0%.The fabrication technique for these ceramics is conventional and stable.

Effects of NaNbO_3-Co_2O_3 Co-additive on the Properties of PZN-PZT Ceramics

NaNbO3-Co2O3 co-added PZN-PZT （PZCNNT） ceramics were prepared using conventional solid state reaction. The piezoelectric and dielectric properties were measured. The experimental results show that the addition of 0.3mo1% Co2O3 leads to low dielectric loss （tgδ） in PZCNNT ceramics and the proper addition of NaNbO3 not only improves piezoelectric properties but also decreases intensively dielectric loss and mechanical loss. The optimal ceramic having d33=310 pC/N, kp=0.59, εr=985, tgδ=0.0034, Qm=1380 was obtained.

Effect of Zr^(4+)on piezoelectric,dielectric and ferroelectric properties of barium calcium titanate lead-free ceramics

Ba_(0.85)Ca_(0.15)(Ti1−xZrx)O_(3)(BCTZ)ceramics with x=0.05,0.10,_(0.15),0.20,0.25,0.30 were prepared by the solid-state reaction method.Calcination of the powders was carried out at 1100°C for 4 h and the green pellets were sintered at 1400°C for 2 h.X-ray diffraction patterns of the sintered pellets showed tetragonal splitting up to x=0.10 while the mixture of the rhombohedral/cubic phase appeared at higher ZrO_(2)concentrations.Maximum piezoelectric charge constant d33=510 pC/N and strain(S=0.103%)were measured for BCT doped by 0.10 mol ZrO_(2).Dielectric constant,remnant polarization and saturation polarization also found maxima for this composition.The Curie temperature(TC)of the compositions decreased with increase in ZrO_(2)concentration and reached 98°C,87°C and 36°C at x=0.05,0.10,_(0.15)mol,respectively.The remaining compositions have TC below the room temperature;therefore,they can be used for subzero/cryogenic applications.The scanning electron microscopy study revealed an increase in grain size with increase in ZrO_(2)concentration and confirmed the complete solubility of ZrO_(2)in the crystal lattice.Overall,low ZrO_(2)-doped BCT compositions with high d33 could be suitable for low temperature(<80°C)applications.

Tailoring depolarization temperature by phase transition causing properties evolution in Bi_(0.5)(Na_(1-x)K_(x))_(0.5)TiO_(3)ceramics

(Bi_(0.5)Na_(0.5))TiO_(3)-based materials have attracted widespread attention due to large electro-strain,large remnant polarization(P r)and high Curie temperature(T C),but the existence of inherent depolarization temperature(T d)limits the temperature stability and application temperature range.In this work,we find that K/Na ratio can regulate T d(from 90℃to 246℃)of the ceramics,which confirms that the increase of K substitution can effectively improve the temperature stability of the material.The phase structure and electrical properties of Bi_(0.5)(Na_(1-x)K_(x))_(0.5)TiO_(3)(BNKT x)ceramics can be well modulated by changing K/Na.In addition,BNKT x system exhibits excellent piezoelectric response at morphotropic phase boundary(MPB)of 20%BKT content(d_(33)=180 pC/N),where rhombohedral(R 3 c)phase and tetragonal(P 4 bm)phase coexist in MPB.With K further substitution,BNKT x ceramics transform into tetragonal phase,and the domain size grows due to the structural transition from short-range-correlated P 4 bm to long-range-correlated P 4 mm.The deferment of T d is also tightly related to the increase of P 4 mm/P 4 bm ratio.This work can provide an effective way to tailor depolarization temperature and electrical properties of BNT-based ceramics.