Temperature Dependence Of Ferroelectric Properties Research Articles

The thermal depolarization behavior of PMN-PT-BZT relaxor ferroelectric ceramics from the standpoint of domain structure transitions

The thermal depolarization behavior of PMN-PT-5BZT relaxor ferroelectric ceramics was studied, and the depolarization mechanism was discussed from the perspective of domain structure transitions. In addition to the transition from MPB structure at room temperature to cubic phase at high temperature, the structure symmetry of PMN-PT-5BZT ceramics has no obvious change with increasing temperature. However, the ceramic had experienced a transition process from ferroelectric state to nonergodic relaxor state, and then to ergodic relaxor state. The results of temperature dependence of ferroelectric properties showed that the depolarization temperature Td corresponds to the transition temperature TF-NR from ferroelectric state to nonergodic relaxor state, and there is an obvious dielectric abnormal peak at this temperature, which is mainly due to the depolarization behavior caused by the decrease of macrodomain size and the beginning of transition to nanodomains.

Thickness scaling of (Al0.8Sc0.2)N films with remanent polarization beyond 100 μC cm−2 around 10 nm in thickness

The temperature dependence of ferroelectric properties was investigated for (Al0.8Sc0.2)N films 9–130 nm thick prepared on (111)Pt/TiO x /SiO2/Si substrates. The coercive fields (E c) of these films decreased with increasing measurement temperature up to 523 K, irrespective of film thickness, thus realizing polarization switching because the applicable maximum electric field is beyond E c. As a resultant, remanent polarization (P r) above 100 μC cm−2 was ascertained for 9 nm thick films at 373 and 423 K, which is more than 5 times larger than those of HfO2-based films of the same thickness. The P r value was almost independent of film thickness when an electric field is applied for switching. In addition, E c showed a smaller thickness dependence than conventional ferroelectrics, including Pb(Zr,Ti)O3. The large P r value beyond 100 μC cm−2 for around 10 nm thick films with small degradation against film thickness, as well as the diminished increase in E c with decreasing film thickness. This showed that (Al0.8Sc0.2)N film is a promising candidate for nonvolatile memory applications requiring high-density and low-voltage operation, including capacitor-type memories and ferroelectric tunnel junction-type memories that consist of metal–ferroelectric–metal structure.

Temperature dependence of ferroelectric property and leakage mechanism in Mn-doped Pb(Zr0.3Ti0.7)O3 films

High-quality ferroelectric films of Mn-doped Pb(Zr0.3Ti0.7)O3 (PMZT) were prepared using the sol-gel method, and the temperature dependence of ferroelectric, dielectric, and leakage current properties (J–E) were explored in detail using the top electrode/ferroelectric films/bottom electrode capacitor heterostructure. The enhancement of polarization and dielectric properties by element doping is clearly observed by 3% Mn-doping. Such enhancement is beneficial for the application of these films in ferroelectric random-access memory. In addition, the analysis of leakage current reveals symmetric behavior with 3% Mn-doping and the leakage current density gradually increases with increasing temperature, which may be due to the movement of domain wall and oxygen vacancy. The dominant leakage current conduction mechanism is bulk-limited ohmic or interface-limited Schottky emission conduction within a wide temperature range. The results might be meaningful for further work on ferroelectric electrical devices with improved ferroelectric and dielectric properties.

Electrical Characterization Induced by Structural Modulation in␣(Ca0.28Ba0.72)2.5–0.5x (Na0.5K0.5) x Nb5O15 Ceramics

(Ca0.28Ba0.72)2.5–0.5x (Na0.5K0.5) x Nb5O15 ceramics (CBNKN, 0.0 ≤ x ≤ 0.4) with ‘unfilled’ tungsten bronze structure were prepared by the conventional solid-state reaction method. Effects of alkalis-introducing concentration in A-sites on the microstructure, dielectric and ferroelectric properties were investigated in detail. Pure tungsten bronze structure could be obtained in all compositions according to the x-ray diffraction patterns. Raman spectroscopy results showed that co-introducing Na+ and K+ in A sites to decrease the structural vacancy could enhance the dielectric and ferroelectric properties, which was attributed to the stronger interaction inside NbO6 octahedron and large distortion degree of NbO6 polar unit. Traditional temperature dependence of dielectric characteristics and well-saturated ferroelectric hysteresis loops were observed for all CBNKN ceramics. The better comprehensive dielectric and ferroelectric properties were obtained at x = 0.2 due to the bigger distortion degree of NbO6 polar unit and the highest densification. Whereas higher alkalis-introducing concentration would deteriorate the physical and electrical properties due to the poor sintering behavior. In addition, the frequency dependence of e around transition temperature (T c) and the temperature dependence of ferroelectric properties were discussed to further clarify the relationship between composition and performance.

Temperature Dependence of Ferroelectric Properties of Li<SUB>2</SUB>CO<SUB>3</SUB> Doped PZT–PZN–PMnN Ceramics

Temperature Dependence of Ferroelectric Properties of Li<SUB>2</SUB>CO<SUB>3</SUB> Doped PZT–PZN–PMnN Ceramics

Structural modulation and electrical properties in ferroelectric niobates (Ca0.28Ba0.72)2.5−0.5xKxNb5O15 (0.0≤x≤0.6) ceramics

(Ca0.28Ba0.72)2.5−0.5xKxNb5O15 ceramics (CBKN, 0.0≤x≤0.6) with ‘unfilled’ tungsten bronze structure were prepared by the conventional solid-state reaction method. Effects of K+ concentration on the microstructure, dielectric and ferroelectric properties were investigated. It was found that modulating K+ in A sites to decrease the structural vacancy could enhance the dielectric and ferroelectric properties, which was attributed to the stronger interaction inside NbO6 octahedron and more distortion degree of NbO6 polar unit confirmed by the Raman spectroscopy results. While higher K+ concentration would deteriorate the physical and electrical properties due to the poor sintering behavior caused by the emergence of some larger anisometric pillar-type grains. Traditional temperature dependence of dielectric characteristics and well-saturated ferroelectric hysteresis loops were observed for all CBKN ceramics. The better comprehensive dielectric and ferroelectric properties were obtained at x=0.5 due to the bigger distortion degree of NbO6 polar unit and the highest densification. In addition, the frequency dependence of ε around transition temperature (Tc) and the temperature dependence of ferroelectric properties were discussed to further clarify the relationship between composition and performance.

Temperature dependence of ferroelectric properties and the activation energy of polarization reversal in (Pr,Mn)‐codoped BiFeO3 thin films

We applied Vopsaroiu's model to (Bi,Pr)(Fe,Mn)O3 (BPFM) and Pb(Zr,Ti)O3 (PZT) ferroelectric thin films fabricated by chemical solution deposition. The temperature dependences of the saturation polarization and the coercive field were measured in a low‐temperature region from 100 to 200 K. The saturation polarizations of BPFM thin films decreased on decreasing the measurement temperature due to the polarization pinning effect, while that of PZT thin film was almost unchanged over the temperature region. The coercive fields of all the thin films were increased linearly on decreasing the measurement temperature. The activation energies for polarization reversal in as‐grown BPFM, postannealed BPFM, and PZT thin films were 1.18, 1.25, and 0.95 eV, respectively. These results indicate that BPFM thin films have large activation energies for polarization reversal compared with PZT thin films. In addition, the postannealed BPFM thin film has a larger activation energy than the as‐grown BPFM thin film.

Both electric field and temperature independent behavior of piezoelectric property of Pb(Ni1/3Nb2/3)O3–PbTiO3

The temperature stability of electromechanical properties is an important issue of major concern for the design of actuators. In this paper, temperature dependence of ferroelectric properties have been investigated in the (1−x)Pb(Ni1/3Nb2/3)O3–xPbTiO3 (x=0.30–0.38) solid solutions. Interestingly, the unipolar strain in the composition of x=0.38 shows a good linear relationship with increasing electric field, and the large-signal d33 is independent with increasing temperature from room temperature to 100°C. Furthermore, it also exhibits a very high piezoelectric coefficient d33=450pC/N near the morphotropic phase boundary. All above indicates the present system of (1−x)Pb(Ni1/3Nb2/3)O3–xPbTiO3 may be a kind of potential application for precisely controlling actuators.

Temperature dependence of ferroelectric properties of SBT thin films

Abstract Strontium bismuth tantalate (SBT) thin films have been deposited on Pt/TiO2(100)Si substrates by a metal–organic decomposition (MOD) method, using a non-stoichiometric composition. The measured net spontaneous polarization is a consequence of the parallel alignment of 180° domains, as it is confirmed by the random distribution of the pole figures. Measurements of temperature dependence of permitivitty, e′, and remnant polarization, Pr, show diverse anomalies. The large shift of the temperature TC, is explained by the structure distortion associated with Bi:Sr ratio of the film. A strong decrease of Pr with T is observed that could be related with possible phase transitions, although more information on atomic level is needed to know the mechanisms involved.

Temperature dependence of ferroelectric properties of SrBi2Ta2O9 thin films

Temperature dependence of ferroelectric properties was studied on SrBi2Ta2O9 thin films with stoichiometric composition and Sr deficient and/or Bi excess compositions. Decreasing rate of remanent polarization Pr with increasing temperature was fairly small for the 20% Sr deficient compositions compared to the stoichiometric Sr content compositions. The large Pr decrease for the stoichiometric compositions was attributed to the increase of fast polarization relaxation with increasing temperature. Fatigue-free property was confirmed even at 150 °C for all compositions.