Broadband dielectric spectroscopy of PbMg1/3Nb2/3O3–PbSc1/2Nb1/2O3 ceramics

Abstract Broadband dielectric spectroscopy results of various ordered and disordered (1 − x)Pb(Mg1/3Nb2/3)O3–(x)Pb(Sc1/2Nb1/2)O3 (PMN–PSN) ceramics are investigated in the temperature range from 80 K to 300 K and frequency range from 20 Hz to 2 THz. Dielectric dispersion is very broad and in the ferroelectrics case (x = 1, 0.95) consists of two parts: low-frequency part caused by ferroelectric domains and higher frequency part caused by soft mode. The relaxational soft mode exhibits pronounced softening close to phase transition temperature, as it is typical for order–disorder phase transitions. By substituting Sc3+ by Mg2+ in PMN–PSN ceramics relaxation slows down, and for relaxors (x = 0.…

Distribution of relaxation times in 0.5PMN-0.5PSN ceramics

Dielectric properties of chemically ordered and disordered 0.5PbMg1/3Nb2/3O3-0.5 PbSc1/2Nb1/2O3 (0.5PMN-0.5PSN) ceramics were investigated in frequency range from 20 Hz to 3 GHz by dielectric spectroscopy. The broad dielectric dispersion, similar to this typically obtained for relaxor ferroelectrics (RFE), was observed in both ceramics below 350 K. The frequency dependence of dielectric permittivity of these ceramics were analyzed in terms of the distribution of relaxation times and showed the splitting into two components at lower temperatures. The longest relaxation times part slows down following Vogel-Fulcher law with lower freezing temperature compare with typical RFE like PbMg1/3Nb2/3…

Broadband Dielectric Investigation of Sodium Potassium Niobate Ceramic Doped 8% of Antimony

In this work we present dielectric permittivity measurement results of KNN ceramic doped antimony (K0.5Na0.5)(Nb0.92Sb0.08)O3 with sintering aid MnO2 (0.5 mol% MnO2) (KNNSbx + 0.5Mn). Its dielectric properties were investigated in broad frequency (from 20 Hz to 32 GHz) and temperature (from 26 K to 780K) ranges. Above room temperature obtained results show two diffused phase transitions. Below room temperature investigation revealed dielectric permittivity dispersion similar to the relaxor one. The obtained mean relaxation times fulfills Arrhenius relationship with dipole activation energy Ea/kB = 2282 K.

Soft mode in PMN–PSN ceramics

Various ordered and disordered (1–x)Pb(Mg1/3Nb2/3)O3 –x Pb(Sc1/2Nb1/2)O3 (PMN–PSN) ceramics were studied by THz transmission spectroscopy in the temperature range of 10–300 K. It is found that the dielectric relaxation dominates in the spectra in higher temperatures, T > 170 K. In contrast, below 150 K, the strength of relaxation becomes so weak that the phonon contribution can be separated. The phonon contributribution in the investigated frequency range (200 GHz–2 THz) is presumably caused by the E component of the Last mode. The component exhibits hardening on cooling in all investigated ceramics and its critical temperature in ferroelectric PMN–PSN ceramics (x = 1, 0.95) is lower than t…

Chemical strain effects and changed lattice dynamic in (Sr1-1.5xBix)TiO3ceramics (x ≤ 0.15)

ABSTRACTIn this work lattice strain (induced by chemical Bi substitution on A-site) effects on the lattice dynamic of SrTiO3 ceramics were investigated by broadband dielectric spectroscopy in the very broad frequency range from 10 mHz up to 30 GHz and temperatures from 30 K to 500 K. Obtained results confirmed predicted induce of the ferroelectricity and suppression of the structural phase transition due to substitution of A-site ions – chemical straining of the lattice, both happening at the local scale but evident in macroscopic dielectric spectroscopy measurements. Calculated relaxation time distribution function broadens towards the longest relaxation times with temperature decrease and…

Broad Distribution of Relaxation Times in 0.6PMN-0.4PZN Relaxor Ceramics

In this paper dielectric spectra of 0.6PMN-0.4PZN ceramic obtained from broadband dielectric spectroscopy is presented. Measurements revealed an unusual relaxor like nature. Two different processes in the dielectric spectra have been observed. High frequency, or short relaxation times, behaviour is typical for ferroelectric crystals. Longest relaxation times do not follow Vogel—Fulcher dependence, which is unusual for relaxors.

Dipolar Glass-Like Perovskite Sr0.8Bi0.2TiO3Ceramic

In this work lead-free Sr0.8Bi0.2TiO3 ceramic have been investigated in the frequency range from 20 Hz to 36 GHz. The obtained results show pronounced dispersion below room temperature. It looks more similar to the one observed in dipolar glasses as in relaxors. Calculated relaxation time distribution function broadens towards longest relaxation times with decreasing temperature. The obtained most probable relaxation time fulfills Vogel-Fulcher relationship with the following parameters: dipole activation energy EA/kB = 1718 K, freezing temperature T0 = 65 K, attempt relaxation time, referring to dipole relaxation at very high temperatures, τ0 = 5.5·10−14 s.

Broadband Dielectric Spectroscopy of Ferroelectric Phase Transitions in PbSc1/2Nb1/2O3Ordered Ceramics

Broadband dielectric spectroscopy of PbSc 1/2 Nb 1/2 O 3 (PSN) ordered ceramics are reported within the range of 20 Hz ≤ ν ≤ 2 THz in 80 K ≤ T ≤ 300 K temperatures. Spectrally very broad dielectric dispersion consisting of two parts − at lower frequencies, ferroelectric domains cause a dispersion and at higher frequencies, higher temperatures the relaxation soft mode is responsible for the dispersion. The relaxation soft mode exhibit pronounced hardening on cooling, whilst the ferroelectric phase transition is connected with an abrupt freezing and rise of polar nanoregions into ferroelectric domains.

Distribution of the relaxation times of the new relaxor 0.4PSN–0.3PMN–0.3PZN ceramics

Abstract The real distribution function of the relaxation times g ( τ ) of the relaxor ferroelectric ceramics 0.4PSN–0.3PMN–0.3PZN is calculated from the experimental dielectric spectra obtained in the frequency range from 20 Hz to 1.25 GHz. Below the Burns temperature T B  ≅ 380 K, where the clusters begin to appear on cooling, the distribution of the relaxation times is symmetrically shaped. On cooling, the permittivity and loss spectra strongly broaden and slow down. The g ( τ ) function becomes asymmetrically shaped and the second maximum appears. The width of the g ( τ ) function is calculated at different temperatures. The shortest relaxation time is of the order of 10 −12  s and it r…

Anomalous Broad Distribution of Relaxation Times in Mixed PMN-PSN Ceramics

Dielectric permittivity of 0.8PMN-0.2PSN ceramic was measured in the frequency range from 20 Hz to 3 GHz. The typical ferroelectrics relaxor dielectric dispersion was observed. From the frequency dependence of complex dielectric permittivity, the distribution of relaxation times was calculated. The low frequency limit of the distribution of relaxation times diverges according to the Vogel–Fulcher law with the freezing temperature T f = 226 K which is lower than in PMN ceramics, obtained previously. The comparison of distributions of relaxation times between 0.8PMN-0.2PSN and pure PMN tends to the conclusion about smaller polar nano regions in 0.8PMN-0.2PSN ceramic.

Broadband Dielectric Spectroscopy of PSN-Rich PMN-PSN Ceramics

The broadband dielectric permittivity of ordered 0.1PMN-0.9PSN and disordered 0.2PMN-0.8PSN ceramics was investigated. The anomaly of dielectric permittivity is clearly seen in the region of 370 K for 0.1 PMN-0.9 PSN at all frequencies. 0.2 PMN-0.8 PSN shows relaxor behaviour with huge frequency dispersion below 350 K. Calculated distribution of relaxation times shows noticeable influence of polar nano regions to the total dielectric spectrum below 320 K with the longest relaxation times edge diverging according to the Vogel-Fulcher law. In 0.1 PMN-0.9 PSN two a little overlapped peaks present in the distribution of relaxation times, influenced by displacive lead motions at high frequencies…

Dielectric investigation of lead‐free perovskite strontium titanate with 25% bismuth ceramics

In this work lead-free 0.75SrTiO3-0.25BiTiO3 ceramics have been investigated in broad frequency range. Obtained results showed pronounced dispersion below room temperature typical for the dipolar glasses. The calculated relaxation time distribution function broadens toward longest relaxation times part on cooling. The obtained most probable relaxation time diverges according to the Vogel-Fulcher relationship with the following parameters: dipole activation energy EA=2123 K, glassy state temperature T0=52.7 K, shortest relaxation time, referring to dipole relaxations at very high temperatures, τ0=2.1·10–14 s. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Dielectric investigation of sodium potassium niobate ceramic doped 7% of antimony

Abstract Electric properties of sodium potassium niobate ceramic doped antimony (Na0.5K0.5)(Nb0.93Sb0.07)O3 with sintering aid MnO2 (0.5 mol% MnO2) (KNNSbx + 0.5Mn) were investigated in a broad frequency (from 1 Hz to 54 GHz) and temperature (from 110 K to 800 K) ranges. The mean relaxation times calculated from the dielectric permittivity measurements fulfill Arrhenius relationship with dipole activation energy EA = 3409 K (EA/kB = 0.29 eV). The DC conductivity has been extracted from experimental results and the activation energy was calculated EA = 11733.78 K (EA/kB = 1.011 eV).

Terahertz Spectroscopy of Ordered PbSc1/2Nb1/2O3Ceramics

Broadband dielectric spectroscopy of PSN ceramics

Abstract The complex dielectric permittivity of ordered and disordered PSN ceramics was measured in the frequency range from 20 Hz to 3 GHz. The anomaly of dielectric permittivity is clearly seen in the region of 115 °C for ordered PSN at all measured frequencies. Disordered PSN exhibits typical relaxor behaviour with a huge frequency dispersion below 125 °C. Calculated distribution of relaxation times shows noticeable influence of polar clusters to the total dielectric spectrum of disordered PSN below 80 °C with the longest relaxation times edge diverging according to the Vogel–Fulcher law. In the case of ordered PSN, two almost not overlapping peaks in the distribution of relaxation times…

Dynamics of Polar Clusters in PMN Ceramics: Comparison with PMN Single Crystal

The dielectric permittivity of PMN ceramics was measured in the frequency range from 20 Hz to 37 GHz. From the frequency dependence of the real and imaginary parts of dielectric permittivity, the distribution of relaxation times f(τ) was calculated. The f(τ) function broadens significantly, and the second maximum appears below the 270 K temperature. The dielectric response and also relaxation time distribution of PMN ceramics was compared with the previous results of PMN single crystal. The results showed that dynamics of polar nano regions in PMN ceramics is suppressed due to the small size of grains in the ceramics.