Tin-modified Lead Zirconate Titanate Research Articles

Phase Transition Experimental and Theoretical Study of Micro Power Generator Supplying Source for CMOS Chip Based on Ferroelectric Ceramic Nano-Porous Material.

We demonstrated both experimentally and in theory analysis and calculation that the tin-modified lead zirconate titanate nanoporous ferroelectric generator system can perform as a micro-power supplying source for CMOS chip. The ferroelectric ceramic phase transition under transverse shock wave compression can charge external storage capacitor. The nanoporous microstructure ferro-electric ceramic micro-pulsed-power system is capable of generating low output voltage pulses and supplying CMOS chip with micro power sources. We developed the methodology for theory analysis and experimental operation of the ferroelectric generator. Analysis of the porous ferroelectric ceramic material was carried out by X-ray diffractometry and X-ray photoelectron spectroscopy. Microstructures and surface morphology of porous ferroelectric ceramics samples were examined by using scanning electron microscopy. The planar shock wave experiments were conducted on a compressed-gas gun. The experimental results were in good agreement with the theory analysis. Keywords: PSZT Ferroelectric Ceramic, Shock Wave, Phase Transition, Depolarization, Micro-Power-Generator.

EFFECTS OF SHOCK PRESSURE AND SELF-GENERATED ELECTRIC FIELD ON SHOCK-INDUCED FERROELECTRIC TO ANTIFERROELECTRIC PHASE TRANSITION IN LEAD ZIRCONATE STANNATE TITANATE FERROELECTRIC CERAMICS

Kinetics of the ferroelectric (FE) to antiferroelectric (AFE) phase transformation under shock wave compression is critical to design the shock-activated power supply and can be characterized in terms of both a transition rate and a limiting degree of transition. By measuring the depoling currents under the short-circuit and high-impedance conditions, we investigated the influence of shock pressure and self-generated electric field on the phase transition kinetics of tin-modified lead zirconate titanate ceramics (Pb0.99Nb0.02[(Zr0.90Sn0.10)0.96Ti0.04]0.98O3) in the pressure range from 0.23 to 4.50 GPa. Experimental results indicate that the shock pressure promotes the FE-to-AFE phase transition. And the self-generated electric field does not appear to have a significant effect on the depoling currents at high shock pressures, but has a strong effect at low pressures. At 0.61 GPa and 1.03 GPa, transition rate and degree diminish with increasing the electric field, illustrating that the self-generated electric field suppresses the FE-to-AFE phase transition. These observations are found to be generally consistent with results under the hydrostatic compression. Fundamental issues are discussed from the perspective of the soft mode theory.

Self-generated electric field suppressing the ferroelectric to antiferroelectric phase transition in ferroelectric ceramics under shock wave compression

Kinetics of the ferroelectric (FE) to antiferroelectric (AFE) phase transformation under shock wave compression is critical to design the shock-activated power supply and can be characterized in terms of both a transition rate and a limiting degree of transition. By measuring the depoling currents under the short-circuit and high-impedance conditions, we investigated the influence of self-generated electric field on the phase transition kinetics of tin-modified lead zirconate titanate ceramics (Pb0.99Nb0.02[(Zr0.90Sn0.10)0.96Ti0.04]0.98O3) in the pressure range from 0.61 to 4.50 GPa. Experimental results indicate that the self-generated electric field does not appear to have a significant effect on the depoling currents at high shock pressures, but has a strong effect at low pressures. At 0.61 and 1.03 GPa, transition rate and degree diminish with increasing the electric field, illustrating that the self-generated electric field suppresses the FE-to-AFE phase transition. These observations are found to be generally consistent with many ferroelectric materials and results under hydrostatic compression. Fundamental issues are discussed from the perspective of the soft mode theory.

Electrical Behavior of PSZT Ferroelectric Ceramic under Shock Wave Compression

Electric power of hundreds of kilowatts can be produced in a few microseconds by sudden release of bound charge on the surface of ferroelectric ceramic through shock wave compression. In order to understand the depolarization process, knowledge of the discharge behavior of ferroelectric ceramic under shock wave compression is essential. Gas-gun facility has been used to investigate the shock-induced depolarization kinetics of tin-modified lead zirconate titanate ferroelectric ceramic. Experiments were conducted in the normal mode in which the shock propagation vector was perpendicular to the remanent polarization. Two kinds of specimens with the ferroelectric-toantiferroelectric transformation hydraulic pressure respectively at 80 MPa and 180 MPa were tested. The output currents as a function of load resistance were measured. A computation model was developed to describe the electrical behavior of PSZT ceramic under shock wave compression, which adequately explained the observed experimental results.

Phase Transition Characters in Tin Modified Lead Zirconate Titanate Compounds

Antiferroelectric materials of double electric hysteresis could be used to large displacement actuator, discharge capacitor and transducer. Phase transition characters induced with electric field and temperature were studied in lager tin modified lead zirconate titanate compounds Pb 0.99 Nb 0.02 [(Zr 0.60 Sn 0.40 ) 1 − x Ti x ] 0.98 O 3 . Antiferroelectric composition range of double hysteresis was measured at x ≤ 0.064. Differing from lower tin modified PZST the permittivity formed a hathpace at high temperature region in Pb 0.99 Nb 0.02 [(Zr 0.60 Sn 0.40 ) 1 − x Ti x ] 0.98 O 3 family. This dielectric hathpace was caused by a transitional paraelectric phase which depressed the sharp Curie peak. Dielectric hathpace became higher and narrower as x component increasing.

Electric field effect on the rhombohedral–rhombohedral phase transformation in tin modified lead zirconate titanate ceramics

The ferroelectric–to–ferroelectic phase transformation between the high temperature (FERH) and the low temperature (FERL) rhomobohedral phases in lead based perovskite under the dc bias conditions was investigated. Dielectric measurements show that an external electric field stabilizes the FERL phase and moves the phase transformation to a higher temperature. The observation has been further verified by an in situ microfocused x-ray study where an external field can effectively induce the oxygen octahedral tilting in the crystalline lattice and extends the thermal stability region of the FERL phase to a higher temperature. An analysis based on the combination of the Clausius–Clapeyron relationship with lattice dynamic principles suggests that the transformation from FERH to FERL is driven by a short-range interaction in the crystalline lattice. The origin of this short-range interaction is proposed, based on the structural evolution during the phase transformation. Experimental evidence suggests that such interaction driving the structural instability can be exploited by an external electric field near the phase transformation temperature and leads to an unusual, transient field-enhanced deformation near the FERH/FERL phase transformation.

Field-enhanced piezoelectric deformation during the high temperature/low temperature rhombohedral (FERh/FERL) phase transformation for tin modified lead zirconate titanate ceramics

An unusual field-enhanced piezoelectric deformation near the FERH/FERL structural phase transformation was observed in a tin modified lead zirconate titanate solid solution. In addition to the typical field-induced domain reorientation and the piezoelectric strain, this additional field-enhanced deformation only observed near the phase transformation increases linearly with external electric field strength. A 78% increase in field-enhanced strain was observed at a field strength of 32 kV/cm. Comparison of the dielectric susceptibility at low and high field conditions suggests that the observed unusual behavior is created by a field-induced lattice softening during the structural phase transformation. Experimental observations on the field-induced softening phenomena are reported.

Thermal expansion in lead zirconate titanate

The volume anomalies with temperature variations in tin-modified lead zirconate titanate ceramics are investigated. Experimental results show that the volume changes are related to the phase transitions induced with temperature. The magnitude and orientation of crystal volume changes are dependent on the particular phase transition. When antiferroelectrics is transformed to ferroelectrics or paraelectrics the volume expands. Oppositely when ferroelectrics is transformed to antiferroelectrics or paraelectrics the volume contracts. In the transition of antiferroelectric orthorhombic structure to tetragonal structure or ferroelectric low-temperature rhombohedral structure to high-temperature rhombohedral structure, there are also revealed apparent anomalies in the curves of thermal expansion. Among them, the volume strain caused by the transition between antiferroelectrics and ferroelectrics is the biggest in magnitude, and the linear expansion dL/L0 and the expansion coefficient (dL/L 0)/dT can reach 2.8 × 10−3 and 7.5 × 10−4 K−1 respectively.

Microstructural Evolution under Polarization Switching of Ferroelectric Tin-modified Lead Zirconate Titanate Ceramics

Electric fatigue properties of ferroelectric niobium-doped tin-modified lead zirconate titanate (PNZST) ceramics were investigated using polarization-electric field (P–E) measurements, and the corresponding microstructure evolution was studied employing transmission electron microscopy. The results show that domain boundaries are induced under repeated electric field application, and the microstructures become more complicated due to domain intersection. The mobility of domain boundaries degrades and the polarization of the material decreases because the intersection of domain boundaries introduces enormous strain fields and defects in the materials. A large number of dislocations and microcracks were observed in some regions when the specimens were repeatedly loaded for 106 cycles. In contrast, the remanent polarization of the ferroelectric PNZST degraded to 83% of its initial value and only half of the degraded polarization was recoverable after a refresh treatment, indicating that defects in grains play important roles in fatigue properties.

Incommensurately Modulated Polar Structures in Antiferroelectric Tin‐Modified Lead Zirconate Titanate: II, Dependence of Structure‐Property Relations on Tin Content

Studies of the structure‐property relations in Pb0.98Nb0.02‐ [(Zr1‐xSnx)0.97Ti3]1‐zO3 (PZST x/3/2) were performed for 0 < x < 0.50 by transmission electron microscopy, dielectric spectroscopy, and electrically induced polarization and strain methods. As the tin content increased, a general sequence of changes in phase stability was observed, including (i) a ferroelectric rhombohedral (FEr) phase (x < 0.15), (ii) a coexistence of FEr and antiferroelectric incommensurate (AFEin) states (x = 0.15), and (iii) an AFEin state (x > 0.15). Evidence will be presented that incommensurately modulated structures become pinned into long‐lived metastable states by quenched tin impurities, rather than evolving toward a commensurate phase. Maximum electrically induced strains (epsilon) and polarizations (P) were found in the compositional range of x similar/congruent 0.15, where FEr and AFEin regions coexisted. Values of epsilon as large as 0.5% were found at field strengths of <80 kV/cm. In addition, these studies demonstrated evidence for two electrically induced phase transitions (x = 0.15): (i) an antiferroelectric‐ferroelectric (AFE‐FE) transition near 40 kV/cm, and (ii) a secondary ferroelectric‐ferroelectric (FE‐FE) transition near 60‐80 kV/cm. The dominate contribution to epsilon was associated with the secondary transition, whereas the dominate contribution to P was associated with the first. For x < 0.15, evidence of an induced FE‐FE transition was found. For x > 0.15, an induced AFE‐FE transition was evident. However, no indications of a secondary FE‐FE transition were observed. Large epsilon values were not induced until field levels significantly greater than that required to induced polarization saturation were obtained, which indicates a decoupling of epsilon and P.

The effect of external field symmetry on the antiferroelectric-ferroelectric phase transformation

The antiferroelectric (AFE)-ferroelectric (FE) phase transformation under dc bias and hydrostatic pressure conditions in tin-modified lead zirconate titanate ceramics [Pb(Zr,Sn,Ti)O3, i.e., PZST] was investigated. The shifting of transformation temperature under these conditions and an electric field induced lattice softening are reported. Depending on the symmetry of external applied fields, the thermal stability region of one phase can be expanded at the expense of another. Experimental results indicate that a symmetric external field (such as hydrostatic pressure) tends to stabilize the AFE phase region, whereas an asymmetric external field (such as electric field) tends to extend the FE phase region. These observations are found to be generally consistent with many ferroelectric and antiferroelectric materials exhibiting a displacive structural phase transformation. Results are compared with the Clausius–Clapeyron relationship, and fundamental issues underlying the thermodynamic relationship and field-induced lattice softening behavior are discussed from the perspective of lattice dynamics theory.

An incommensurate-commensurate phase transformation in antiferroelectric tin-modified lead zirconate titanate

Antiferroelectric tin-modified lead zirconate titanate ceramics (PZST), with 42 at. % Sn and 4 at. % Ti, were studied by hot- and cold-stage transmission electron microscopy and selected area electron diffraction techniques. The previously reported tetragonal antiferroelectric state is shown to be an incommensurate orthohombic state. Observations revealed the existence of incommensurate 1/x 〈110〉 superlattice reflections below the temperature of the dielectric maximum. The modulation wavelength for this incommensurate structure was found to be metastably locked-in near and below room temperature. An incommensurate-commensurate orthorhombic antiferroelectric transformation was then observed at lower temperatures. However, an intermediate condition was observed over a relatively wide temperature range which was characterized by an intergrowth of 〈110〉 structural modulations, which was strongly diffuse along the 〈110〉. These structural observations were correlated with dispersion in the dielectric properties in the same temperature range. No previous reports of an incommensurate orthorhombic antiferroelectric state or an incommensurate-commensurate orthorhombic antiferroelectric transformation are known to exist.

Incommensuration in antiferroelectric tin-modified lead zirconate titanate

Abstract The temperature dependence of the crystal structures of tin-modified lead zirconate titanate ceramics Pb(0.98)Nb0.02[Zr1−x,Snx)1−yTiy]1−zO3 was investigated by hot-stage transmission electron microscopy. The composition chosen for study, x=0.42 and y=0.04 (i.e., PZST 42/4/2), had a sequence of phase transformations on heating of antiferroelectric - multicell cubic - simple cubic. The presence of the multicell cubic phase was characterized by the existence of weak ½[110] superlattice spots in the temperature range between the antiferroelectric and simple cubic phases. The antiferroelectric phase in both compositions was characterized by the presence of one-dimensional regular arrays of antiphase domain boundaries and 1/x[110] superlattice spots. The modulation wavelength for the superlattice spot was found to be a strong function of temperature and was incommensurate with the lattice.

Electrically-Induced Strains in Sn-Modified Lead Zirconate Titanate

AbstractIncommensuate antiferroelectric tin-modified lead zirconate titanate ceramics, PbNb0.02[(Zr1−x,Snx)1−yTiy]0.98O3, have been studied by Sawyer-Tower polarization and electrically-induced strain (ε-E) techniques. Sawyer-Tower polarization studies revealed antiferroelectric-ferroelectric (AFE-FE) P-E loops. Investigations then revealed that the electrically-induced strain associated with the AFE-FE transformation was not realized until field strengths significantly above that required for polarization saturation. It is believed that the electrically-induced strain is decoupled from the polarization due to AFEFE switching by the modulation of the phase of a <110> incommensurate structure. At field strengths above saturation, the commensurate rhombohedral ferroelectric state is believed to be induced from an incommensurate orthorhombic ferroelectric, and the electrically-induced strain is then realized.

Hot-stage transmission electron microscopy studies of phase transformations in tin-modified lead zirconate titanate

The temperature dependence of phase stability for tin-modified lead zirconate titanate solid solution ceramics Pb(0.98)Nb0.02[(Zr1−x, Snx)1−yTiy]1−zO3 (PZST) was investigated by hot-stage transmission electron microscopy. Compositions studied included, a material that was antiferroelectric (AFE) at room temperature with x=0.42 and y=0.04, and a material that was ferroelectric (FE) at room temperature with x=0.43 and y=0.08 (abbreviated as PZST 42/4/2 and 43/8/2, respectively). PZST 42/4/2 was found to exhibit a sequence of phase transformations on heating of AFE–multicell cubic (MCC)–simple cubic (SC), whereas PZST 43/8/2 had a sequence of FE-AFE-MCC-SC. Previously referred to F spots (i.e., 1/2[111] superlattice spots) were observed in all four phases. The diffraction intensities for the F spots decreased with increasing temperature, and eventually disappeared above 300 °C. Electron diffraction confirmed the presence of the MCC phase which was characterized by the existence of weak 1/2[110] superlattice spots in the temperature region between the AFE and SC phases. In each composition the AFE phase was characterized by arrays of one-dimensional antiphase domain boundaries and (1/x)[110] superlattice spots. The modulation wavelength for the superlattice spots was found to be a strong function of temperature and was incommensurate with the lattice. The thermal stability of phases in the crystalline solution PZST system is discussed in terms of the observed microstructural features.

Thermal stability of field-forced and field-assisted antiferroelectric-ferroelectric phase transformations in Pb(Zr,Sn,Ti)O3

Antiferroelectric (AFE)-ferroelectric phase transformations in tin-modified lead zirconate titanate, i.e., Pb(Zr,Sn,Ti)O3 are reported. A martensitic-type approach is developed to explain the observed thermal hysteresis and field-induced transformation behavior. A model is proposed with transformation fields where the forward EF and reverse EA field strengths are related to the transformation barrier to the ferroelectric state, and to the AFE sublattice coupling, respectively. The thermal stability of the AFE state can therefore be determined with respect to the field-induced transformation behavior. A distinction is made between field-forced and field-assisted transformations, which depend on temperature and thermal hysteresis, and which are related to reversible and irreversible field-induced characteristics. Data are reported for polarizations and strains, and discussed with respect to the proposed thermodynamic model and device applications.