Temperature dependence of electrical and electromechanical properties of Pb(Mg1/3Nb2/3)O3–Pb(Ni1/3Nb2/3)O3–Pb(Zr,Ti)O3 thin films

The electrical and electromechanical properties of Pb(Mg_1/3Nb_2/3)O₃–Pb(Ni_1/3Nb_2/3)O₃–Pb(Zr,Ti)O₃ (PMN–PNN–PZT, PMN/PNN/PZT = 20/10/70) on Pt/Ti/SiO₂/Si substrates by chemical solution deposition was investigated. The PMN–PNN–PZT films annealed at 650 °C exhibited slim polarization hysteresis curves and a high dielectric constant of 2100 at room temperature. A broad dielectric maximum at approximately 140–170 °C was observed. The field-induced displacement was measured by scanning probe microscopy, the bipolar displacement was not hysteretic, and the effective piezoelectric coefficient (d₃₃) was 66 × 10⁻¹² m/V. The effective d₃₃ decreased with temperature, but the value at 100 °C remained 45 × 10⁻¹² m/V.     

Effects of addition of Pb(Y1/2Nb1/2)O3 (PYN) on microstructure and piezoelectric properties of Pb(Zr0.53Ti0.47)O3

Pure and Pb(Y_1/2Nb_1/2)O₃ (PYN)-doped Pb(Zr_0.53Ti_0.47)O₃ have been characterized. The samples were prepared by conventional mixed-oxide ceramic technology. PYN dopant was added to PZT at content levels ranging from 1 to 2.5 mol%. The microstructures of the samples were examined using SEM and TEM. The average grain size was observed to decrease as the dopant content increased. Herringbone-like and wedge-shaped domain patterns were observed in all the samples. The piezoelectric properties of PZT were greatly improved by the addition of PYN. The highest piezoelectric constant d₃₁ was nearly twice that of pure PZT.     

Fabrication and characterization of (Pb(Mg1/3Nb2/3)O3, Pb(Yb1/2Nb1/2)O3, PbTiO3) ternary system ceramics

New ternary compositions in the Pb(Mg_1/3Nb_2/3)O₃-Pb(Yb_1/2Nb_1/2)O₃–PbTiO₃ (PMN-PYbN-PT) system were prepared using 0.5Pb(Yb_1/2Nb_1/2)O₃-0.5PbTiO₃ (PYbNT) and (1-x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃ (x = 0.26; PMNT26 or x = 0.325; PMNT32.5) powders synthesized via the columbite method. Dense (≥ 96% of theoretical density) ceramics with PMN/PYbN mole ratios of 25/75 (R-25), 50/50 (R-50) and 75/25 (R-75T and R-75R) were fabricated by reactive sintering at 1000 °C for 4 h. Therefore, incorporation of PYbNT to PMNT successfully decreased sintering temperature of PMNT from 1200 °C-1250 °C to 1000 °C. Samples with higher density and perovskite ratio together with lower weight loss possessed higher dielectric and piezoelectric values in each composition. The R-75 samples had remanent polarization (P_r) values of 34-36 μC/cm² and piezoelectric charge coefficient (d₃₃) of 560 pC/N. The sharp phase transition PMNT as a function of temperature became broader or more diffuse with increasing PYbNT content. However, PYbNT addition to PMNT increased Curie temperature (T_c) from 183 °C (for PMNT32.5) to 220-242 °C (for R-75T and R-75R) to 336 °C (for R-25). Therefore, these ternary compositions can be tailored for various high temperature applications due to the relatively higher T_c with enhanced piezoelectric and dielectric properties as compared to PMNT.     

Piezoelectric properties of Pb(Mn1/3Nb2/3)O3–PbZrO3–PbTiO3 ceramics with sintering aid of 2CaO–Fe2O3 compound

Since the electromechanical devices move towards enhanced power density, high mechanical quality factor (Q_m) and electromechanical coupling factor (k_p) are commonly needed for the high powered piezoelectric transformer with Q_m≥2000 and k_p=0.60. Although Pb(Mn_1/3Nb_2/3)O₃–PbZrO₃–PbTiO₃ (PMnN–PZ–PT) ceramic system has potential for piezoelectric transformer application, further improvements of Q_m and k_p are needed. Addition of 2CaO–Fe₂O₃ has been proved to have many beneficial effects on Pb(Zr,Ti)O₃ ceramics. Therefore, 2CaO–Fe₂O₃ is used as additive in order to improve the piezoelectric properties in this study. The piezoelectric properties, density and microstructures of 0.07Pb(Mn_1/3Nb_2/3)O₃–0.468PbZrO₃–0.462PbTiO₃ (PMnN–PZ–PT) piezoelectric ceramics with 2CaO–Fe₂O₃ additive sintered at 1100 and 1250 °C have been studied. When sintering temperature is 1250 °C, Q_m has the maximum 2150 with 0.3 wt.% 2CaO–Fe₂O₃ addition. The k_p more than 0.6 is observed for samples sintered at 1100 °C. The addition of 2CaO–Fe₂O₃ can significantly enhance the densification of PMnN–PZ–PT ceramics when the sintering temperature is 1250 °C. The grain growth occurred with the amount of 2CaO–Fe₂O₃ at both sintering temperatures.     

Phase diagram and properties of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 polycrystalline ceramics

yPb(In_1/2Nb_1/2)O₃-(1 − x − y)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (yPIN-(1 − x − y)PMN-xPT) polycrystalline ceramics with morphotropic phase boundary (MPB) compositions were synthesized using columbite precursor method. X-ray diffraction results indicated that the MPB of PIN-PMN-PT was located around PT = 0.33-0.36, confirmed by their respective dielectric, piezoelectric and electromechanical properties. The optimum properties were found for the MPB composition 0.36PIN-0.30PMN-0.34PT, with dielectric permittivity ?_r of 2970, piezoelectric coefficient d₃₃ of 450 pC/N, planar electromechanical coupling k_p of 49%, remanent polarization P_r of 31.6 μC/cm² and T_C of 245 °C. According to the results of dielectric and pyroelectric measurements, the Curie temperature T_C and rhombohedral to tetragonal phase transition temperature T_R-T were obtained, and the “flat” MPB for PIN-PMN-PT was achieved, indicating that the strongly curved MPB in PMN-PT system was improved by adding PIN component, offering the possibility to grow single crystals with high electromechanical properties and expanded temperature usage range (limited by T_R-T).     

Processing and properties of Pb(Mg1/3Nb2/3)O3–PbTiO3-based ceramics

Ceramic compositions of a combination between lead magnesium niobate, Pb(Mg_1/3Nb_2/3)O₃, and lead titanate, PbTiO₃, were fabricated using the Mg₄Nb₂O₉ precursor technique. Their electrical properties with respect to temperature and frequency were examined and the effect of sintering conditions on phase formation, densification, microstructure and electrical properties of the ceramics were examined. It has been found that optimisation of sintering conditions can lead to a highly dense and pyrochlore-free PMN–PT ceramics. The gradual decrease of the physical properties of the sintered ceramics was related to the gradual decrease of density and inhomogeneous microstructure. The results also revealed that for the lower concentration of lead titanate, a relaxor behaviour is noticed with a high electrostrictive effect, which was almost hysteretic free. However, higher amount of lead titanate led to a normal ferroelectric behaviour.     

Anisotropic field induced phase transitions and negative electrocaloric effect in rhombohedral Mn doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

The electrocaloric effect (ECE) of Mn doped Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT:Mn) single crystals with particular emphasis on the impact of crystallographic orientations and phase transitions were investigated systematically. Orientation-dependent phase transitions have been demonstrated by the dielectric and strain behaviors. Intriguingly, the negative ECE of –0.02?°C and –0.002?°C were obtained firstly in [001]-oriented PIN-PMN-PT:Mn crystals near the rhombohedral→tetragonal phase transformation and in [011]-oriented crystals near the rhombohedral→orthorhombic phase transformation, respectively. However, only the positive ECE was found in [111]-oriented crystals near the tetragonal→rhombohedral phase transition. Additionally, the maximum ECE temperature changes calculated in [001]-, [011]- and [111]-oriented crystals were 0.33?°C, 0.46?°C and 0.38?°C, respectively. Our results suggest that the negative ECE is attributed to electric field-induced phase transitions, whose critical field decreases with the increase of temperature. The phase transition-mediated coexistence of positive and negative effects in the relaxor-ferroelectric single crystals is beneficial to enhance the efficiency of the solid-state cooling devices.     

Linear response fluorescent temperature-sensing properties based on Stark sublevels of Er3+-doped Pb(Mg1/3Nb2/3)O3-PbTiO3-Pb(Yb1/2Nb1/2)O3 ceramics

The Er³⁺ doped 0.84(PMN-PT)?0.14PYN ceramics were employed as a temperature-sensing material. The obtained compounds exhibit strong visible upconversion (UC) fluorescence under a 980-nm diode laser excitation. On account of the Stark split effect, the ²H_11/2, ⁴S_3/2, and ⁴F_9/2 levels of Er³⁺ split into two Stark sublevels, respectively. The fluorescence intensity ratios (FIR) between these sublevels were calculated in a temperature range of 133–573?K, and a linear FIR vs. temperature relation has been found. FIR of A/B shows a wide temperature sensing range with a relatively low sensitivity of 0.003?K^?1. Meanwhile E/C illustrates the highest sensitivity of 0.0134?K^?1 but in the smallest temperature range 453–573?K. FIR technique provides us a optical thermometric method with constant sensitivity in a wide temperature range.     

Investigation of ternary system Pb(Sn,Ti)O3-Pb(Mg1/3Nb2/3)O3 with morphotropic phase boundary compositions

(1 − x)Pb(Sn_1−yTi_y)O₃-xPb(Mg_1/3Nb_2/3)O₃ (x = 0.1-0.4, y = 0.45-0.65) ternary system was prepared using two-step columbite precursor method. Phase structure of the synthesized ceramics was studied by using X-ray powder diffraction and the morphotropic phase boundary (MPB) curve of the ternary system was confirmed. The isothermal map of Curie temperature (T_C) in the phase diagram was obtained based on the dielectric-temperature measurements. The coercive field E_C and internal bias field E_i were found to increase with increasing PT content, while decrease with increasing PMN content. The optimum properties were achieved in the MPB composition 0.8Pb(Sn_0.45Ti_0.55)O₃-0.2Pb(Mg_1/3Nb_2/3)O₃, with dielectric permittivity ?_r, piezoelectric coefficient d₃₃, planar electromechanical coupling k_p, mechanical quality factor Q_m and T_C of being on the order of 3040, 530pC/N, 55.5%, 320 and 190 °C, respectively, exhibiting potential usage for high power application.     

The hydration of 11CaO · 7Al2O3 · CaF2 AT 20°C

Hydration at 20°C of C₁₁A₇ · CaF₂ which exists in regulated set cement was investigated by means of conduction calorimetry, differential thermal analysis, scanning electromicroscopic observation, X-ray diffraction and chemical analysis. The process of hydration and rate of hydration were determined and influence of the various calcium sulfates, calcium hydroxide and carboxylic acid upon the hydration of C₁₁A₇ · CaF₂ was discussed. Mechanism of the strength development was also deduced in relation to the structure of hardened paste.     

Structural investigation and dielectric studies on Mn substituted Pb(Zr0.65Ti0.35)O3 perovskite ceramics

Polycrystalline samples of manganese substituted lead zirconium titanate (PZMT) with general formula Pb(Zr_0.65−xMn_xTi_0.35)O₃ ceramics have been synthesised by high temperature solid state reaction technique. X-ray diffraction (XRD) patterns were recorded at room temperature to study the crystal structure employing Rietveld technique. All the patterns could be refined to R3c space group with rhombohedral symmetry. Bond lengths and angles have been calculated from refined parameters. Microstructural properties of the materials were analysed by scanning electron microscope (SEM) and compositional analysis were carried out by energy dispersive spectrum (EDS) measurements. All the materials exhibit ferroelectric to paraelectric transition. The Curie temperature (T_c) increases with the Mn concentration. We have observed that dielectric constant decreases and AC conductivity increases with the frequency. The correlation between lattice parameters and T_c for the present samples has been observed.     

The influence of sintering aids for Nd(Mg0.5Ti0.5)O3 microwave dielectric ceramics properties

The influence of various sintering aids on the microwave dielectric properties and the structure of Nd(Mg_0.5Ti_0.5)O₃ ceramics were investigated systematically. B₂O₃, Bi₂O₃, and V₂O₅ were selected as liquid-phase sintering aids to lower the sintering temperature. The sintered Nd(Mg_0.5Ti_0.5)O₃ ceramics are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and microwave dielectric properties. The sintering temperature of Nd(Mg_0.5Ti_0.5)O₃ microwave dielectric ceramics is generally high, about 1500 °C. However, the sintering temperature was significantly lowered about 175 °C from 1500 °C to 1325 °C by incorporating in 10 mol% B₂O₃ and revealed the optimum microwave dielectric properties of dielectric constant (_r) value of 26.2, a quality factor (Q × f) value of 61,307 (at 9.63 GHz), and τ_f value of −45.5 ppm/°C. NdVO₄ secondary phase was observed at 10 mol% V₂O₅ addition in the sintering temperature range of 1300–1325 °C, which led the degradation in microwave dielectric properties. The microwave dielectric properties as well as grain sizes, grain morphology, and bulk density were greatly dependent on sintering temperature and various sintering aids. In this study, it is found that Nd(Mg_0.5Ti_0.5)O₃ incorporated with 10 mol% B₂O₃ with lower sintering temperature and excellent dielectric microwave properties may be suggested for application in microwave communication devices. The use of liquid-phase sintering, the liquid formed during firing normally remains as a grain boundary phase on cooling. This grain boundary phase can cause a deterioration of the microwave properties. Therefore, the selection of a suitable sintering aid is extremely important.     

Effect of Bi2O3 and B2O3 additives on the sintering temperature, microstructure, and microwave dielectric properties for Sm(Mg0.5Ti0.5)O3 ceramics

The microwave dielectric properties of Sm(Mg_0.5Ti_0.5)O₃ incorporated with various amount of Bi₂O₃ and B₂O₃ additives have been investigated systematically. In this study, both Bi₂O₃ and B₂O₃ additives acting as a sintering aid can effectively lower the sintering temperature from 1550 °C to 1300 °C. The ionic radius of Bi³⁺ for a coordination number of 6 is 0.103 nm, whereas the ionic radius of B³⁺ is 0.027 nm. Clearly, the ionic radius of Bi³⁺ is greatly larger than one of B³⁺, which resulted in the specimens incorporated with Bi₂O₃ having larger lattice parameters and cell volume than those incorporated with B₂O₃. The experimental results show that no second phase was observed throughout the entire experiments. Depending on the interfacial tension, the liquid phase may penetrate the grain boundaries completely, in which case the grains will be separated from one another by a thin layer as shown in Sm(Mg_0.5Ti_0.5)O₃ ceramics incorporated with Bi₂O₃. Whereas, in Sm(Mg_0.5Ti_0.5)O₃ ceramics incorporated with B₂O₃, the volume fraction of liquid is high, the grains may dissolve into the liquid phase, and rapidly rearrange, in which case contact points between agglomerates will be dissolved due to their higher solubility in the liquid, leading plate-like shape microstructure.A dielectric constant (?_r) of 29.3, a high Q × f value of 26,335 GHz (at 8.84 GHz), and a τ_f of −32.5 ppm/°C can be obtained for Sm(Mg_0.5Ti_0.5)O₃ ceramics incorporated with 10 mol% Bi₂O₃ sintered at 1300 °C. While Sm(Mg_0.5Ti_0.5)O₃ ceramics incorporated with 5 mol% B₂O₃ can effectively lower temperature coefficient of resonant frequency, which value is −21.6 ppm/°C. The Sm(Mg_0.5Ti_0.5)O₃ ceramic incorporated with heavily Bi₂O₃ and B₂O₃ additives exhibits a substantial reduction in temperature (∼250 °C) and compatible dielectric properties in comparison with that of an un-doped one. This implied that this ceramic is suitable for miniaturization in the application of dielectric resonators and filters by being appropriately incorporated with a sintering aid.     

Effect of Bi2O3 additives on sintering and microwave dielectric behavior of La(Mg0.5Ti0.5)O3 ceramics

Bi₂O₃ was selected as liquid phase sintering aid to lower the sintering temperature of La(Mg_0.5Ti_0.5)O₃ ceramics. The sintering temperature of La(Mg_0.5Ti_0.5)O₃ ceramics is generally high, about 1600 °C. However, the sintering temperature was significantly lowered about 275 °C from 1600 °C to 1325 °C by incorporating in 15 mol% Bi₂O₃ and revealed the optimum microwave dielectric properties of dielectric constant (?_r) value of 40.1, a quality factor (Q × f) value of 60,231 GHz, and the temperature coefficient (τ_f) value of 70.1 ppm/°C. During all addition ranges, the relative dielectric constants (?_r) were different and ranged from 32.0 to 41.9, the quality factors (Q × f) were distributed in the range of 928–60,231 GHz, and the temperature coefficient (τ_f) varies from 0.3 ppm/°C to 70.3 ppm/°C. Noticeably, a nearly zero τ_f can be found for doping 5 mol% Bi₂O₃ sintering at 1325 °C. It implies that nearly zero τ_f can be achieved by appropriately adjusting the amount of Bi₂O₃ additions and sintering temperature for La(Mg_0.5Ti_0.5)O₃ ceramics.     

Piezoelectric properties of low temperature sintering in Pb(Zr,Ti)O3–Pb(Zn,Ni)1/3Nb2/3O3 ceramics for piezoelectric transformer applications

In this study, in order to develop low-temperature sintering ceramics for a multilayer piezoelectric transformer application, we explored CuO and Bi₂O₃ as sintering aids at low temperature (900 °C) sintering condition for Sb, Li and Mn-substituted 0.8Pb(Zr_0.48Ti_0.52)O₃–0.16Pb(Zn_1/3Nb_2/3)O₃–0.04Pb(Ni_1/3Nb_2/3)O₃ ceramics. These substituted ceramics have excellent piezoelectric and dielectric properties such as d₃₃  347 pC/N, k_p  0.57 and Q_m  1469 when sintered at 1200 °C. The addition of CuO decreased the sintering temperature through the formation of a liquid phase. However, the piezoelectric properties of the CuO-added ceramics sintered below 900 °C were lower than the desired values. The additional Bi₂O₃ resulted in a significant improvement in the piezoelectric properties. The composition Sb, Li and Mn-substituted 0.8Pb(Zr_0.48Ti_0.52)O₃–0.16Pb(Zn_1/3Nb_2/3)O₃–0.04Pb(Ni_1/3Nb_2/3)O₃ + 0.5 wt% CuO + 0.5 wt% Bi₂O₃ showed the value of k_p = 0.56, Q_m = 1042 (planar mode), d₃₃ = 350 pC/N, when it was sintered at 900 °C for 2 h. These values indicated that the newly developed composition might be suitable for multilayer piezoelectric transformer application.     

Fabrication and electrical properties of Pb(Co1/3Nb2/3)O3 ceramics

Pb(Co_1/3Nb_2/3)O₃ (PCN) ceramics have been produced by sintering PCN powders synthesized from lead oxide (PbO) and cobalt niobate (CoNb₂O₆) with an effective method developed for minimizing the level of PbO loss during sintering. Attention has been focused on relationships between sintering conditions, phase formation, density, microstructural development, dielectric and ferroelectric properties of the sintered ceramics. From X-ray diffraction analysis, the optimum sintering temperature for the high purity PCN phase was found at approximately 1050 and 1100 °C. The densities of sintered PCN ceramics increased with increasing sintering temperature. However, it is also observed that at very high temperature the density began to decrease. PCN ceramic sintered at 1050 °C has small grain size with variation in grain shape. There is insignificant change of dielectric properties with sintering temperature. The P–E hysteresis loops observed at −70 °C are of slim-loop type with small remanent polarization values, which confirmed relaxor ferroelectric behavior of PCN ceramics.     

High dielectric permittivity and electrostrictive strain in a wide temperature range in relaxor ferroelectric (1-x)[Pb(Mg1/3Nb2/3)O3-PbTiO3]-xBa(Zn1/3Nb2/3)O3 solid solutions

High electric field-induced strain with ultralow hysteresis, which is often generated based on electrostrictive effects in ferroelectric materials, is highly desired due to its potential applications in high-precision displacement actuators. In this paper, (1-x)[Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃]-xBa(Zn_1/3Nb_2/3)O₃ [(1-x)(PMN-PT)-xBZN] ceramics were fabricated by a solid-state reaction method. The effect of Ba(Zn_1/3Nb_2/3)O₃ (BZN) content on dielectric and electrostrictive properties in relaxor ferroelectric PMN-PT solid solutions was investigated in detail by dielectric spectra, polarization-electric field (P-E) hysteresis loops and strain-electric field (S-E) curves. With an increasing BZN content, the temperature stability of the dielectric permittivity of (1-x)(PMN-PT)-xBZN is improved due to the formation of two coexistent phases. A high electrostrictive strain (~0.17% at 60?kV/cm) with an ultralow hysteresis (<10%) characteristic is obtained in a composition where x?=?0.1725. The strain versus polarization (S-P) curves measured from 30?°C to 130?°C can be well fitted based on a quadratic relation, suggesting the dominating role of the electrostrictive effect. The longitudinal electrostrictive coefficient Q₃₃ for this system ranges from 0.0254?m⁴/C² to 0.0318?m⁴/C². Our results suggest that (1-x)(PMN-PT)-xBZN ferroelectric ceramics are potential candidates for applications in capacitors and high-precision displacement actuators.     

Structural and electrical properties of 0.56Pb(Ni1/3Nb2/3)O3-0.10Pb(Zn1/3Nb2/3)O3-0.34PbTiO3 ceramics prepared by different ceramic processings

The ternary system of 0.56Pb(Ni_1/3Nb_2/3)O₃-0.10Pb(Zn_1/3Nb_2/3)O₃-0.34PbTiO₃ (0.56PNN-0.10PZN-0.34PT) ceramics were prepared by conventional solid-state reaction method via straight mixed oxide method, columbite precursor method and B-site oxide mixing route. X-ray diffraction (XRD) measurement demonstrated that both the tetragonal and rhombohedral phases coexist in the B-site oxide mixing route prepared ceramics accompanied by the largest content of perovskite phase of 95.18%. The 0.56PNN-0.10PZN-0.34PT ceramics prepared by the straight mixed oxide method and the B-site oxide mixing route exhibit rather homogeneous microstructure. As a comparison, in the columbite precursor method prepared ceramics nebulous granules and octahedral or other polyhedral morphology grains are observed. All the sintered ceramics exhibit diffused ferroelectric phase transition where the dielectric response peaks are broad, diffused and strongly frequency dependent. However, the temperature of dielectric maximum (T_m) increases greatly from 398.0 K of the 0.56PNN-0.10PZN-0.34PT ceramics prepared by the B-site oxide mixing route to 423.3 K of the ones prepared by the straight mixed oxide method. Saturated and symmetric P-E hysteresis loops are observed in all the sintered ceramics, where the B-site oxide mixing route prepared ceramics exhibit large value of remanent polarization (P_r) of 17.13 μC/cm² and the least value of coercive field (E_c) of 11.99 kV/cm. Piezoelectric constant (d₃₃) exhibits the largest value of 449 pC/N for the ceramics prepared by the B-site oxide mixing route. Such results are related to the phase composition, density and porosity of the ceramics.     

Temperature induced dielectric polarization evolution in polycrystalline Pb(Cd1/3Nb2/3)O3

The results of X-ray diffraction (XRD), scanning electron microscopy (SEM), dilatometric and dielectric measurements performed for the same polycrystalline Pb(Cd_1/3Nb_2/3)O₃ (PCN) sample are presented. These results reveal the complex character of polycrystalline PCN dielectric properties; in particular, no structural phase transition (PT) was observed. The thermal expansion coefficient indicates glass-like behaviour of PCN. The frequency and temperature dependencies of complex dielectric permittivity were measured and analyzed in terms of diffused/relaxor transition of the ferroelectric polarization. Temperature induced evolution of the relative dielectric permittivity was found to involve two processes. Dielectric permittivity changes, originating from thermally induced evolution of thermal equilibrium of interactions between main structural lattice and two sub-lattices present in the sample were interpreted in terms of thermal evolution of polar cluster sizes in the region of relaxor/glass-like transition.     

Microstructural, electrical and magnetic properties of multiferroic CoFe2O4/0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 nanocomposite thin films

Bilayered CoFe₂O₄/0.68Pb(Mg_1/3Nb_2/3)O₃-0.32PbTiO₃ nanocomposite films are successfully prepared on Pt/Ti/SiO₂/Si substrate via simple sol-gel process. X-ray diffraction result reveals that there exists no chemical reaction or phase diffusion between the CoFe₂O₄ and 0.68Pb(Mg_1/3Nb_2/3)O₃-0.32PbTiO₃ phases. The microstructure is characterized by scanning/transmission electron microscopy (STEM). The composite thin films exhibit both strong ferroelectric and ferromagnetic responses at room temperature. The maximal magnetoelectric coupling coefficient of the nanocomposite films reaches up to 25 mV/cm Oe, occurs at a lower bias magnetic field (H_dc) of 550 Oe.