Zr-rich Lead Zirconate Titanate Research Articles

Mode Coupling at around M-Point in PZT.

The question of the microscopic origin of the M-superstructure and additional satellite peaks in the Zr-rich lead zirconate-titanate is discussed for nearly 50 years. Clear contradiction between the selection rules of the critical scattering and the superstructure was found preventing unambiguous attributing of the observed superstructure either to the rotation of the oxygen octahedra or to the antiparallel displacements of the lead cations. Detailed analysis of the satellite pattern explained it as the result of the incommensurate phase transition rather than antiphase domains. Critical dynamics is the key point for the formulated problems. Recently, the oxygen tilt soft mode in the PbZrTiO (PZT2.4) was found. But this does not resolve the extinction rules contradiction. The results of the inelastic X-ray scattering study of the phonon spectra of PZT2.4 around M-point are reported. Strong coupling between the lead and oxygen modes resulting in mode anticrossing and creation of the wide flat part in the lowest phonon dispersion curves is identified. This flat part corresponds to the mixture of the displacements of the lead and oxygen ions and can be an explanation of the extinction rules contradiction. Moreover, a flat dispersion surface is a typical prerequisite for the incommensurate phase transition.

Structural Peculiarities of the Intermediate Phase in Zr-Rich Lead Zirconate Titanate

This paper presents the results of X-ray diffraction studies on a single crystal of lead zirconate titanate PbZr0.993Ti0.007O3 in the region of existence of an intermediate ferroelectric phase. In addition to the known superstructure reflections of the M type qM = $$\left\{ {\frac{1}{2},\frac{1}{2},0} \right\}$$ and the first-order satellite reflections qM + {δ, δ, δ}, unknown second-order satellites have been observed near qM and near the Bragg reflections. Structural model of regular system of antiphase domains is used for diffraction calculation. The model is shown to describe the first- and second-orders satellite reflections in the vicinity of qM, but it cannot explain the appearance of satellites around the main Bragg peaks. A possible origin of the system of the superstructures observed in the intermediate phase is discussed.

Incommensurate instability and diffuse scattering at Brillouin zone boundary in Zr-rich lead zirconate titanate

Detailed study of the X-ray diffuse scattering in the paraelectric phase of the PbZr0.985Ti0.015O3 was carried out. We concentrated on the analysis of the scattering peculiarities in the vicinities of M- and R- points of the Brillouin zone. We have observed a critical increase of the diffuse scattering at the position Q ≈ (0.47 + h 0.53 + k l) slightly aside of M point on cooling to the intermediate phase. We attribute observed critical scattering to a mixed mode containing both oxygen octahedral tilts and antiparallel cationic displacements. Tentative conclusion is made describing earlier reported complicated set of the satellite peaks around M-point as the result of the soft-mode driven incommensurate phase transition.

Improved pyroelectric figures of merit of Mn-doped Zr-rich lead zirconate titanate bulk ceramics near room temperature for energy harvesting applications

Pyroelectric energy harvesting has been attracting increasing attention due to its abundance and potential applications. In this work, we comparably investigated the pyroelectric properties of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 bulk ceramics without (PNZT95/5) and with Mn doping (PNMZT95/5). Compared to PNZT95/5, PNMZT95/5 demonstrated a lower dielectric constant and low rhombohedral - high rhombohedral ferroelectric phase transition temperature (TLH from 37 °C to 27 °C). Moreover, the poling time displayed significant effects on the dielectric and pyroelectric properties of the ceramics. A giant pyroelectric response was obtained for the PNMZT95/5 ceramics, of which the maximum pyroelectric figure of merit FE was 16017 J/(m3K2) after 180 min of poling, which increased 62% compared with the FE for PNZT95/5 (9890 J/(m3K2), far higher than those of other pyroelectric materials as well. PNMZT95/5 ceramics is suggested to be a promising candidate for the thermal energy harvesting applications.

Temperature scaling of dynamic hysteresis in Zr-rich PbZr1−xTixO3 ceramics

The temperature scaling relations of the dynamic hysteresis were investigated in Zr-rich lead zirconate titanate (PZT) bulk ceramics. At each relation curve, there is a discontinuous district corresponding to the low- and high-temperature phase transitions. The temperatures are divided into low-T region and high-T region. At each temperature region, three power-law scaling relations were obtained for hysteresis area ⟨A⟩, coercivity Ec, and remnant polarization Pr with T, respectively. The six temperature scaling relations are field dependent and the simplified forms are different from the results obtained from the soft and hard PZT ceramics.

Scaling behaviors of dynamic hysteresis in Zr-rich lead zirconate titanate bulk ceramics

The scaling behaviors of the dynamic hysteresis in Zr-rich lead zirconate titanate bulk ceramics at various frequency ( f ) and field amplitude ( E 0 ) values, and in different ferroelectric phases, were investigated. The scaling laws of the hysteresis area 〈 A 〉 at fixed temperature take the forms 〈 A 〉 ∝ f 0.16 E 0 and 〈 A 〉 ∝ f 0.01 E 0 0.2 for low frequency and high frequency, respectively. The forms are different from those of the theoretical predictions and other experimental results but are the same for different ferroelectric phases, which implies that the compositions and crystal structures can influence the scaling laws while the different space groups in the rhombohedral phase can not.

Electron emission and phase transition of Zr-rich lead zirconate titanate ferroelectrics

This letter focuses on understanding the influences of antiferroelectric–ferroelectric (AFE–FE) phase transition on the ferroelectric electron emission process. The piezoelectric constant and electron emission current of un-prepoled PZT 96.5/3.5 ceramics as a function of emission times were studied. The hysteresis loops of PZT 96.5/3.5 ceramics before and after the electron emission process were presented. The results show that emission currents obtained from PZT 96.5/3.5 ferroelectrics in different phase states were similar. It was difficult to explain the experiment results using the fast AFE–FE phase transition model. Electron emission from PZT 96.5/3.5 ferroelectrics was independent of the AFE–FE phase transition.

Fabrication and properties of the Nb doped Zr-rich lead zirconate titanate ceramics by a heterogenous precipitation method

A novel heterogenous precipitation method (H-P) combining the merits of solid state synthesis (S-S-S) and the liquid routes was developed to synthesize ZrO 2 phase-free Nb doped Zr-rich PZT ceramics. The microstructure of the ceramics synthesized by H-P was more homogeneous and fine than for S-S-S. The density and the ferroelectric properties of the ceramics synthesized by H-P were higher than that by S-S-S. The dissipation factor tgδ synthesized by H-P was lower than that by S-S-S. The Weibull distribution analysis shows that the dielectric breakdown of the ceramics synthesized by H-P method is markedly improved.

Dielectric Breakdown Properties of Zr-Rich Lead Zirconate Titanate Ceramics

The series Nb-doped zirconate-rich lead zirconate titanate (PZT) ceramics with high densities up to 97% were fabricated using the traditional solid reaction method. We investigated the dielectric breakdown strength of the series PZT ceramics and detected first that the dielectric breakdown strength increased with an increase in Zr/Ti at the boundary of the antiferroelectric and ferroelectric phases. A qualitative analysis was carried out to discuss the observed phenomena. The relationship between dielectric breakdown and microstructure was also discussed.

Effect of A-Site Substitution of Calcium on Zr-Rich Lead Zirconate Titanate

Effect of calcium substitution on the A-site of Zr-rich lead zirconate titanate Pb(Zr 0.94 Ti 0.06 )O 3 and Pb(Zr 0.92 Ti 0.08 )O 3 is studied. It is found that the rhombohedral structure of Zr-rich lead zirconate titanate changes to tetragonal and finally to cubic with increasing amount of calcium substitution. Both the dielectric constant and the Curie temperature decrease with the substitution of calcium on the A-site of the ABO 3 perovskite structure. A pyroelectric current peak is observed which is resulted from the phase transition from the low temperature rhombohedral ferroelectric phase F R ( LT ) to the high temperature F R ( HT ) one. Small amount of calcium substitution increases the peak value and also shifts the peak position to higher temperatures. However, further increase in the calcium content lowers the peak value and finally smears out the peak.

Preparation of Zr-Rich Pb(Zr,Ti)O 3 Films by Sol-Gel Technique

Zr-rich lead zirconate titanate [Pb(Zr x Ti 1 m x )O 3 (PZT)] ( x =0.9) films were fabricated by sol-gel technique, using lead (II) acetate trihydrate, zirconium (IV) propoxide, and titanium tetraisopropoxide as source materials. Final heat treatment of rapid thermal annealing was done at 735°C for 4 min. PZT films fabricated directly on Ir/SiO 2 /Si substrate had a large grain size of 10-20 w m and bad electric properties, derived by the lack of adhesion. To arrange the adhesion of Ir surface, thin Ti film (∼1 nm) was introduced to Ir surface as a buffer layer. Employing the Ti layer, PZT grain size decreased to less than 1 w m. From the temperature dependence of dielectric constant, Curie temperature was 260°C and dielectric constant at 26°C was 750. Symmetric D - E hysteresis loop was observed, and remanent polarization and coercive field were 20 w C/cm 2 and 65 kV/cm, respectively. Zr-rich PZT film derived from sol-gel technique is expected to apply to ferroelectric memory and pyroelectric devices.

Preparation of Zr-Rich Pb(Zr,Ti)O 3 Films by Sol-Gel Technique

Zr-rich lead zirconate titanate [Pb(Zr x Ti 1 m x )O 3 (PZT)] ( x =0.9) films were fabricated by sol-gel technique, using lead (II) acetate trihydrate, zirconium (IV) propoxide, and titanium tetraisopropoxide as source materials. Final heat treatment of rapid thermal annealing was done at 735°C for 4 min. PZT films fabricated directly on Ir/SiO 2 /Si substrate had a large grain size of 10-20 w m and bad electric properties, derived by the lack of adhesion. To arrange the adhesion of Ir surface, thin Ti film (∼1 nm) was introduced to Ir surface as a buffer layer. Employing the Ti layer, PZT grain size decreased to less than 1 w m. From the temperature dependence of dielectric constant, Curie temperature was 260°C and dielectric constant at 26°C was 750. Symmetric D - E hysteresis loop was observed, and remanent polarization and coercive field were 20 w C/cm 2 and 65 kV/cm, respectively. Zr-rich PZT film derived from sol-gel technique is expected to apply to ferroelectric memory and pyroelectric devices.

Growth of highly (1 0 0)-oriented Zr-rich PZT thin films on Pt/Ti/SiO 2/Si substrates by a simple sol–gel process

Zr-rich lead zirconate titanate thin films with highly preferential (1 0 0) orientation, PZT80/20 and PZT85/15, and randomly oriented PZT70/30 thin films have been successfully prepared on (1 1 1)Pt-coated Si substrates using the sol–gel process with rapid thermal annealing (RTA) at 700°C for 200 s. The results of X-ray diffraction, including rocking curve measurements, suggest that PZT80/20 and PZT85/15 have a single (1 0 0) orientation with the rocking curve FWHM of around 0.5°. The dielectric properties of each film have been measured as well. The results show that highly (1 0 0)-oriented PZT85/15 films exhibit higher remnant polarization (2 P r=41.4 μC/cm 2) and higher coercive field (2 E c=111 kV/cm) than randomly oriented PZT70/30 films (2 P r=33.4 μC/cm 2 and 2 E c=106 kV/cm, respectively).

Dynamical Properties of the FR(LT)-FR(HT) Phase Transition in Zr-Rich Lead Zirconate Titanate Ceramics

The dielectric, elastic and piezoelectric properties of the F R(LT)-F R(HT) phase transition were investigated on Nb-doped lead zirconate titanate (PZT) Pb(Zr1-xTix)O3 ceramics (x=0.05 and 0.25). Dielectric anomaly and thermal hysteresis are observed through the F R(LT)-F R(HT) phase transition in PZT(Nb)95/5, but no anomaly appears in PZT(Nb)75/25. Two compositions show pronounced dielectric dispersions in the rhombohedral ferroelectric phases. The temperature dependences of resonance frequency (f r), elastic constant (s11 E) and Poisson's ratio(σ) show remarkable anomalies around the F R(LT)-F R(HT) phase transition in both compositions. However, the temperature range of the anomaly of PZT(Nb)75/25 is much broader than that of PZT(Nb)95/5. The electromechanical coupling factor (K p) decreases abruptly in PZT(Nb)95/5, while, in contrast, it increases gradually in PZT(Nb)75/25. These results are discussed on the basis of the coupling of M-type and R-type oxygen octahedral tilts to polarization and strain.