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The electrocaloric effect (ECE) has recently become very attractive phenomenon due to its various potential applications, for example in heating or cooling devices of new generation which could be more efficient and environmentally friendly. Here a direct measurements of the ECE in thick films of 8/65/35 PLZT ceramics, and in the relaxor ferroelectric polymer composition P(VDF-TrFE-CFE)0.95-P(VDF-CTFE)0.05 near room temperature are presented. Our results are consistent with those obtained by indirect measurements. The maximum of the ECE responsivity ΔTEC/E in 8/65/35 PLZT thick films is achieved near the critical point, and in the terpolymer/copolymer blends it is shifted toward higher fields.

Presented in this paper of this special issue of Ferroelectrics, dedicated to Prof. Wolfgang Kleemann, is our recent study of thermal response near the dipolar glass to ferroelectric (G-F) transition studied by a high resolution calorimetry in relaxor ferroelectric 9/65/35 PLZT ceramics. By theoretical investigations based on spherical random bond random field (SRBRF) model it is predicted that the discontinuous electrocaloric change (EC) of temperature should be observed at the G-F transition line in an electric field–temperature (E-T) phase diagram. Experimental results confirm existence of such discontinuous EC jump in temperature in the canonical relaxor system 9/65/35 PLZT ceramics, thus confirming the existence of the first order G-F transition line in the E-T phase diagram of the perovskite relaxor ferroelectrics.

In CaCu3Ti4O12 (CCTO), the ceramic material with the highest dielectric permittivity ever reported in a broad frequency and temperature range, the origin of such high permittivity has been attributed to ‘electrical’ heterogeneities in the microstructure. Dielectric investigations of CCTO ceramic thin films, performed in a broad temperature and frequency range, and the analysis in terms of the equivalent circle reveal that (i) each of the two constituents, insulating grain boundaries and semiconducting bulk grains, individually determines the dielectric behaviour of CCTO and (ii) manipulating the conditions under which CCTO ceramic thin films are prepared enables control of their dielectric properties.

KTa 0.6 Nb 0.4 O 3 thin films on polycrystalline alumina were prepared by Chemical Solution Deposition from potassium acetate and transition metal alkoxides in 2-methoxyethanol. Influence of the reflux time on the phase composition, microstructure, and dielectric properties of the films was studied. Films, prepared from the 1 h-refluxed solutions and heated at 900°C have dielectric permittivity value of 860, dielectric losses value of 0.01 and tunability (C 0V / C 30V ) value of 1.9. The corresponding values for the films, prepared from the 24 h-refluxed solutions, are 1690, 0.04, and 2.6, respectively.

We present the first results of FT NIR Raman studies of (K 0.5 Na 0.5 NbO 3 ) 1 − x (SrTiO 3 ) x (x = 0.25, 0.20, 0.15) relaxors made in wide temperature range. Although the crystal structure of the investigated relaxors exhibits a pseudocubic symmetry Raman spectra are observed. The Raman spectra of (K 0.5 Na 0.5 NbO 3 ) 1 − x (SrTiO 3 ) solid solution resemble those observed for orthorhombic K 0.5 Na 0.5 NbO 3 . The results are discussed in the frame of molecular dynamics of NbO 6 octahedral network. It was found that, the changes in dynamics of NbO 6 molecular groups appear at T ≈ 196 K for x = 0.25, T ≈ 254 K for x = 0.20 and T ≈ 336 K for x = 0.15.

The effect of strontium doping in K 0.5 Na 0.5 NbO 3 (KNN) ceramics in the amount of 0.5, 2, 5 and 10 atom % is studied. With increasing dopant content the orthorhombic distortion of the perovskite solid solution is markedly reduced. The density of stoichiometric KNN sintered at 1115°C is 94.4% of TD, doping with 0.5% Sr leads to a 2% higher density, but with higher amounts of Sr the density decreases. The values of ϵ and d 33 for the undoped KNN ceramics are 450 and 80 pC/N, respectively. Sr—doping causes an increase in the dielectric constant, from 500 for KNN-0.5% Sr to 1650 for KNN-5% Sr and a decrease in the d 33 constant from 95 to 50 pC/N.

Dielectric response (100 Hz–1 MHz) and pyroelectric response (light modulation frequency range 10 Hz–1 kHz) of ferroelectric P(VDF/TrFE)(50/50) copolymer loaded with relaxor PLZT 9.5/65/35 ceramic powder of 10 nm crystallite size and ∼700 nm aggregates was studied. Though the dielectric permittivity of the composites increases due to high permittivity of the ceramic, their dielectric response is determined by dielectric relaxation processes of the polymer matrix. The dispersive dielectric anomalies of PLZT-0.9/65/35 relaxor ceramic affect mainly the dielectric absorption of the composites in the range of dipolar relaxation in the crystallite phase of the copolymer. The composites exhibit pyroelectric activity proper for application in operation frequency up to 1 kHz and temperature range 290–310 K.

Pyroelectric response of PVDF and P(VDF 0.5 /TrFE 0.5 )loaded with Pb(Zr 0.5 Ti 0.5 )O 3 ceramic powder of crystallite size ∼30 nm and aggregate size ∼100 nm was studied in light modulation frequency range 1 Hz - 1 kHz. As the ceramic crystallite size is comparable with intrinsic heterogeneity of the polymers we studied also dielectric dispersion and absorption of polymer and composite samples processed the same way. The effect of polymer heterogeneity is discussed and figures of merit of PZT-PVDF and PZT-P(VDF/TrFE) composites are given.

Antiferroelectric lead zirconate films with different thicknesses (0.3 to ≈ 1 μm) were prepared by the sol-gel method. The films were deposited on Pt/TiO2/Si and TiO2/Pt/TiO2/SiO2/Si substrates using a spin coating process. The preferred orientation and the perovskite phase content of the films were studied using X-ray diffraction analysis (XRD). Scanning electron microscopy (SEM) was used for microstructural characterization of the films. Dielectric properties were measured as a function of the temperature and frequency. Antiferroelectricity in the films was confirmed by dielectric double hysteresis loops at room temperature. The influence of precursor and processing parameters on cracking tendency and electrical characteristics of the sol-gel derived lead zirconate films were investigated.

The growth of cracks under the influence of high voltage cyclic electric field in 8/65/35 lanthanum lead zirconate titanate samples was studied. The remanent polarization, coercive field and complex dielectric constant were measured as a function of the number of switching cycles. During the measurement the salt water solution was penetrating through the sample.

Applications of analytical electron microscopy (TEM-EDXS) in investigations of ceramic ferroelectric materials are described and discussed. Emphasis is placed on various PZT and PLZT materials. Mixed oxide and sol-gel derived loose powder, bulk ceramic material and sol-gel derived ferroclectric thin films on various substrates were analyzed and the degree of homogeneity was determined. The influence of TEM sample preparation and the operating conditions of the transmission electron microscope on deterioration of crystal structure, deviation of chemical composition and the formation of a contamination layer are described and discussed.

Piezoelectric PZT ceramics with the addition of 1.3–13.2 vol% ZrO2 were prepared. It was found that the addition of up to 8 vol% ZrO2 leads to higher values of flexural strength as compared to pure PZT, whereas the electric properties of the composites decrease with ZrO2 addition. Both phenomena are explained on the basis of the effect of martensitic transformation of dispersed ZrO2 particles in PZT matrix. Subsequent thermal treatment of the composites leads to lower values of flexural strength and increased electric properties relative to the as fired samples.