Stress-induced shifting of the morphotropic phase boundary in sol-gel derived Pb(Zr0.5Ti0.5)O3 thin films

The structure evolution of Pb(Zr_0.5Ti_0.5)O₃ thin films with different thicknesses on the Pt(1 1 1)/Ti/SiO₂/Si substrates has been investigated using X-ray diffraction and Raman scattering. Differing from Pb(Zr_0.5Ti_0.5)O₃ bulk ceramic with a tetragonal phase, our results indicate that for PZT thin films with the same composition monoclinic phase with Cm space group coexisting with tetragonal phase can appear. It is suggested that tensile stress plays a role in shifting the morphotropic phase boundary to titanium-rich region in PZT thin films. The deteriorated ferroelectric properties of PZT thin films can be attributed mainly to the presence of thin non-ferroelectric layer and large tensile stress.     

Electric and magnetic properties of Pb(Zr0.52Ti0.48)O3-CoFe2O4 particle composite thin film on the SrTiO3 substrate

We deposited a thin epitaxial Pb(Zr_0.52Ti_0.48)O₃ (PZT) layer on the (0 0 1) SrTiO₃ (STO) substrate doped with Nb (0.5 wt.%), then grew composite thin film of CoFe₂O₄ (CFO) and PZT phases on it. X-ray diffraction and high resolution transmission electron microscopy showed that the PZT and CFO phases in the film had perfect epitaxial structures. CFO nanoparticles were embedded in PZT matrix randomly, which was useful to enhance the insulativity of the composite film. The composite thin film exhibited good ferromagnetic and ferroelectric properties. The dielectric constants of the composite thin film kept unchangeable in a wide bias electric field, but increased in a magnetic field, namely, magnetodielectric effect. The possible reasons for the magnetodielectric effect were discussed.     

Magnetoelectric effect in Pb(Zr0.95Ti0.05)O3 and CoFe2O4 heteroepitaxial thin film composite

Multiferroic epitaxial films, include SrRuO₃/Pb(Zr_0.95Ti_0.05)O₃/CoFe₂O₄ has been successfully deposited on SrTiO₃ substrate by pulsed-laser deposition technique. The results show that the prepared films exhibit a single phase. The Pb(Zr_0.95Ti_0.05)O₃ (PZT) film was highly textured with (1 0 0) orientation and gives good ferroelectric properties with saturated polarization of 15 μC/cm². The magnetic coercivity of CoFe₂O₄ film on Pb(Zr_0.95Ti_0.05)O₃ has been dampened to 0.9 kOe. The anisotropic magnetically behavior of CoFe₂O₄ film was changed to isotropic by using high Zr concentrated PZT as underneath layer. Heterostructure films show a good ferromagnetic and ferroelectric coupling that lead to the large magnetoelectricity of 287 mV/cm Oe.     

Effect of annealing ambient on structure and ferroelectric properties of Pb(Zr0.4Ti0.6)O3 thin films on LaNiO3 coated Si substrates

Pb(Zr_0.4Ti_0.6)O₃ [PZT(40/60)] thin films were deposited onto LaNiO₃ (LNO) coated Si substrates by sol-gel technique. Three kinds of gases, air, O₂ and N₂, were used as the annealing ambient. The effect of the annealing ambient on their structure and ferroelectric properties was investigated. The results showed that both the films annealed in air and O₂ were the complete perovskite phase with (1 0 0) preferential orientation, while those annealed in N₂ were random orientation including some pyrochlore phases. As compared with the air ambient, either too much O₂ or too much N₂ was detrimental to the ferroelectric properties of PZT films. The difference in structure and ferroelectric properties was mainly associated with the intermediate phases and the concentration of domain pinning centers in the films.     

Hydrothermal temperature effect on magnetoelectric coupling of Ni/Pb(Zr0.52Ti0.48)O3 bilayers

Magnetoelectric (ME) Ni/Pb(Zr_0.52Ti_0.48)O₃ bilayers have been prepared by hydrothermal method. The structure and ferroelectric properties of the Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films prepared at various hydrothermal temperatures are characterized by X-ray diffraction and ferroelectric testing. With the hydrothermal temperature increasing the grain size of the PZT thin films gradually decreases leading to a gradual increase of the coercive field and a decrease of the remnant polarization of the Ni/PZT bilayers. The ME voltage coefficient of the Ni/PZT bilayers gradually decreases as hydrothermal temperature increases. The large ME coefficient makes these Ni/PZT bilayers possible for applications in multifunctional devices such as electromagnetic sensor, transducers and microwave devices.     

Ferroelectric and pyroelectric properties of (Na0.5Bi0.5)TiO3-BaTiO3 based trilayered thin films

Trilayered Bi_3.25La_0.75Ti₃O₁₂ (25 nm)/(Na_0.5Bi_0.5)_0.94Ba_0.06TiO₃ (300 nm)/Bi_3.25La_0.75Ti₃O₁₂ (25 nm) and Pb(Zr_0.4Ti_0.6)O₃ (25 nm)/(Na_0.5Bi_0.5)_0.94Ba_0.06TiO₃ (300 nm)/Pb(Zr_0.4Ti_0.6)O₃ (25 nm) thin films without undesirable phases have been deposited on Pt/Ti/SiO₂/Si substrates. It was found that the Bi_3.25La_0.75Ti₃O₁₂ and Pb(Zr_0.4Ti_0.6)O₃ layers are very effective to inhibit the charge transport in the trilayered films. Much better insulating properties than those of (Na_0.5Bi_0.5)_0.94Ba_0.06TiO₃ films have been achieved in the trilayered films. The trilayered films show good dielectric, ferroelectric and pyroelectric properties. Remnant polarizations 2P_r of 16 µC/cm² and 34 µC/cm², pyroelectric coefficients of 4.8 × 10^− 4 C m^− 2 K^− 1 and 7.0 × 10^− 4 C m^− 2 K^− 1 have been obtained for the Bi_3.25La_0.75Ti₃O₁₂/(Na_0.5Bi_0.5)_0.94Ba_0.06TiO₃/Bi_3.25La_0.75Ti₃O₁₂ and Pb(Zr_0.4Ti_0.6)O₃/(Na_0.5Bi_0.5)_0.94Ba_0.06TiO₃/Pb(Zr_0.4Ti_0.6)O₃ thin films, respectively. The trilayered films are promising candidates for sensor and actuator applications.     

Magnetoelectric and dielectric properties of Ni0.5Cu0.5Fe2O4–Ba0.5Pb0.5Ti0.5Zr0.5O3 ME composites

The (x) Ni_0.5Cu_0.5Fe₂O₄ + (1−x) Ba_0.5Pb_0.5Ti_0.5Zr_0.5O₃ ME composites have been synthesized by a standard ceramic method. The presence of single phase in x = 0 and x = 1 as well as two phases in x = 0.15, 0.30 and 0.45 composites has been confirmed by XRD. The dielectric constant (ε′) and dielectric loss (tan δ) have been studied as a function of temperature and frequency. These composite materials exhibit maximum dielectric constant with a variation of frequency and temperature. The composite 15% Ni_0.5Cu_0.5Fe₂O₄ + 85% Ba_0.5Pb_0.5Ti_0.5Zr_0.5O₃ had the highest magnetoelectric voltage coefficient of 0.248 mV/cm Oe at room temperature among the studied composites.     

Structural and electrical characterizations of Bi(Zn0.5Ti0.5)O3 doped lead zirconate titanate ferroelectric films with enhanced ferroelectric properties

Bi(Zn_0.5,Ti_0.5)O₃ (BZT) doped Pb(Zr_0.4,Ti_0.6)O₃ (PZT) films were fabricated using a chemical solution deposition method and were characterized intensively in the present work. It was discovered that the room temperature remnant polarization and zero-field longitudinal piezoelectric constant of the BZT-doped PZT film were enhanced by 23% and 30%, respectively, as compared with those of the undoped PZT film prepared under the same experiment conditions. In order to explain the improved ferroelectric properties, the phase structures of the BZT-PZT and undoped PZT films were experimentally investigated in a broad temperature range (from 30 to 600 °C) by using the high temperature two-dimensional X-ray diffraction method. It was found that the improvement in ferroelectricity does not correspond to an elevated Curie temperature (T_C) or a substantially larger tetragonality (c/a). The difference on the change of T_C by doping of Bi-based perovskites in PZT solid solutions between this work and some previous investigations was explained on the basis of Zr/Ti ratio, and the necessity of an in-depth theoretical investigation was addressed.     

Effect of LaNiO3 electrodes and lead oxide excess on chemical solution deposition derived Pb(Zrx,Ti1 − x)O3 films

The effects of LaNiO₃ (LNO) and Pt electrodes on the properties of Pb(Zr_x,Ti_1 − x)O₃ (PZT) films were compared. Both LNO and PZT were prepared by chemical solution deposition (CSD) methods. Specifically, the microstructure of LNO and its influence on the PZT properties were studied as a function of PbO excess. Conditions to minimize the Pyrochlore phase and porosity were found. Remnant polarization, coercive field and fatigue limit were improved in the PZT/LNO films relative to the PZT/Pt films. Additionally, the PZT crystallization temperature over LNO was 500 °C, about ~ 50 °C lower than over Pt. The crystallization temperature reported here is amongst the lowest values for CSD-based PZT films.     

Enhanced ferroelectric properties of Pb(Zr0.80Ti0.20)O3/PbO thin films prepared by radio frequency magnetron sputtering

The Pb(Zr_0.80Ti_0.20)O₃ (PZT) thin films with and without a PbO buffer layer were deposited on the Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrates by radio frequency (rf) magnetron sputtering method. The PbO buffer layer improves the microstructure and electrical properties of the PZT thin films. High phase purity and good microstructure of the PZT thin films with a PbO buffer layer were obtained. The effect of the PbO buffer layer on the ferroelectric properties of the PZT thin films was also investigated. The PZT thin films with a PbO buffer layer possess better ferroelectric properties with higher remnant polarization (P_r = 25.6 μC/cm²), and lower coercive field (E_c = 60.5 kV/cm) than that of the films without a PbO buffer layer (P_r = 9.4 μC/cm², E_c = 101.3 kV/cm). Enhanced ferroelectric properties of the PZT thin films with a PbO buffer layer is attributed to high phase purity and good microstructure.     

Distribution of pyrochlore phase in Pb(Mg1/3Nb2/3)O3-PbTiO3 films and suppression with a Pb(Zr0.52Ti0.48)O3 interfacial layer

Thin films of the relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) on Pt/Ti/SiO₂/Si (Pt/Si) substrates both with and without a Pb(Zr_0.52Ti_0.48)O₃ (PZT) interfacial layer were investigated. Perovskite and pyrochlore coexistence was observed for PMN-PT thin films without a PZT interfacial layer. Interestingly, most of the pyrochlore phase was observed in single-coated films and in the first layer of multi-coated films. The pyrochlore phase exhibited grains with an average size of about 25 nm, which is smaller than those of the perovskite phase (about 90 nm). In contrast, for PMN-PT thin films grown on a PZT interfacial layer, the formation of a pyrochlore phase at the interface between PMN-PT layers and the substrate is completely suppressed. Moreover, small grains are not observed in the films with a PZT interfacial layer. The measured polarization-electric field (P-E) hysteresis loops of PMN-PT films with and without PZT layers indicate that enhanced electrical properties can be obtained when a PZT interfacial layer is used. These enhanced properties include an increase in the value of remanent polarization P_r from 2.7 to 5.8 μC/cm² and a decrease in the coercive field E_c from 60.5 to 28.0 kV/cm.     

Pb(Zr0.52Ti0.48)O3/TiNi multilayered heterostructures on Si substrates for smart systems

Ferroelectric/shape memory alloy thin film multilayered heterostructures possess both sensing and actuating functions and are considered to be smart. In this article, Pb(Zr_0.52Ti_0.48)O₃ (PZT) ferroelectric thin films and Ti-riched TiNi shape memory alloy thin films have been deposited on Si and SiO₂/Si substrates in the 400-600 °C temperature range by pulsed laser deposition technique. Deposition processing, microstructure and surface morphology of these films are described. The TiNi films deposited at 500 °C had an austenitic B2 structure with preferred (110) orientation. The surfaces of the films were very smooth with the root-mean-square roughness on a unit cell level. The structure of the TiNi films had a significant influence on that of the subsequently deposited PZT films. The single B2 austenite phase of the TiNi favored the growth of perovskite PZT films. The PZT/TiNi heterostructures with the PZT and TiNi films respectively deposited at 600 and 500 °C exhibited a polarization-electric field hysteresis behavior with a leakage current of about 2 × 10^− 6 A/cm².     

Large electrocaloric effect of highly (100)-oriented 0.68PbMg1/3Nb2/3O3-0.32PbTiO3 thin films with a Pb(Zr0.3Ti0.7)O3/PbOx buffer layer

0.68PbMg_1/3Nb_2/3O₃-0.32PbTiO₃ (PMN-PT) thin films with a lead zirconate titanate Pb(Zr_0.3Ti_0.7)O₃ (PZT)/PbO_x buffer layer were deposited on Pt/TiO₂/SiO₂/Si substrates by radio frequency magnetron sputtering technique, and pure perovskite crystalline phase with highly (100)-preferred orientation was formed in the ferroelectric films. We found that the highly (100)-oriented thin films possess not only excellent dielectric and ferroelectric properties but also a large electrocaloric effect (13.4 K at 15 V, i.e., 0.89 K/V) which is attributed to the large electric field-induced polarization and entropy change during the ferroelectric-paraelectric phase transition. The experimental results indicate that the use of PZT/PbO_x buffer layer can induce the crystal orientation and phase purity of the PMN-PT thin films, and consequently enhance their electrical properties.     

Fine-grained multiferroic BaTiO3/(Ni0.5Zn0.5)Fe2O4 composite ceramics synthesized by novel powder-in-sol precursor hybrid processing route

Dense, homogeneous, and fine-grained multiferroic BaTiO₃/(Ni_0.5Zn_0.5)Fe₂O₄ composite ceramics are synthesized by a novel powder-in-sol precursor hybrid processing route. This route includes the dispersion of nanosized BaTiO₃ ferroelectric powders prepared via conventional sold-state ceramic process into (Ni_0.5Zn_0.5)Fe₂O₄ ferromagnetic sol-gel precursor prepared via sol-gel wet chemistry process. Uniformly distributed slurry is obtained after ball milling and used in the fabrication of the ceramics with low sintering temperatures. The ceramics show coexistence of ferromagnetic and ferroelectric phases with obvious ferromagnetic and ferroelectric hysteresis loops at room temperature, besides exhibiting excellent magnetic and dielectric properties in a wide range of frequency. The combination of high permeability and permittivity with low losses in the ceramics enables significant miniaturization of electronic devices based on the ceramics.     

Orientation controlling of Pb(Zr<Subscript>0.53</Subscript>Ti<Subscript>0.47</Subscript>)O<Subscript>3</Subscript> thin films prepared on silicon substrates with the thickness of La<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>CoO<Subscript>3</Subscript> electrodes

Pb(Zr_0.53Ti_0.47)O₃ (PZT) thin films were prepared on La_0.5Sr_0.5CoO₃ (LSCO) coated Si substrates by a sol–gel route. The thickness of LSCO electrode was found to modify the preferential orientation of PZT thin films, which consequently affected the dielectric and ferroelectric properties. (100) textured PZT films with dense columnar structure could be obtained on the top of (110) textured LSCO with thickness of 230 nm. PZT thin films prepared on the optimized LSCO films exhibit the enhanced dielectric constant and remnant polarization of 980 and 20 μC/cm², respectively.     

Polarization fatigue and photoinduced current in (Pb0.72La0.28)Ti0.93O3 buffered Pb(Zr0.52Ti0.48)O3 films on platinized silicon

We report a study on the fatigue behavior of Pb(Zr_0.52Ti_0.48)TiO₃ (PZT) films deposited on Pt/Ti/SiO₂/Si substrates by a sol-gel method with single- and double-sided (Pb_0.72La_0.28)Ti_0.93O₃ (PLT) buffer layers, with an attempt to clarify the role of the top and bottom PLT buffer layers on the fatigue endurance (FE) of the PZT films. It is revealed that the existence of the PLT buffer layer and the level of driving alternating-current electric switching field strongly influence the fatigue properties. In terms of the existence of an asymmetric built-in electric field near the top and bottom interfaces between the film and metal electrode, we explain the observed fatigue properties.     

Microstructures, ferromagnetic, and ferroelectric properties in polyvinylpyrrolidone-assisted CoFe2O4/Pb(Zr0.53Ti0.47)O3 multiferroic composite thick films

CoFe₂O₄/Pb(Zr_0.53Ti_0.47)O₃ (CFO/PZT) multiferroic composite thick films with different CFO mass fractions have been prepared onto Pt/Ti/SiO₂/Si substrate by a hybrid sol–gel process and spin coating technique. Polyvinylpyrrolidone (PVP) was employed to be an assistance to the sol–gel solution for enhancing the film thickness and promising a crack-free film surface. After annealing at 650 °C in air for 1 h, phase structure, microstructure, magnetic and ferroelectric properties as well as leakage current of multiferroic thick films were investigated. X-ray diffraction indicated a deeply buried distribution of CFO particles in the PZT matrix. Scanning electronic microscopes showed crack-free surfaces and a decreasing film thickness from 7.2 μm to 6.2 μm with increasing CFO content. Furthermore, the saturated magnetization and remanent magnetization were also hence increased. In addition, mass fraction of CFO in PZT matrix was also estimated from 0.36% to 4.58% according to the relationship between M _s and magnetic content. Ferroelectric hysteresis loops revealed saturated polarization (P _s) and remanent polarization (P _r) were diluted by CFO till its mass fraction rising to 1.8%. After that, polarization was increased with further increasing CFO content. Enhanced leakage was demonstrated to be partially contributed to them. A critical content of 1.8% was hence confirmed, where ferroelectric and magnetic properties can be balanced, indicating a possible stress-transferred magnetoelectric coupling effect in this composite.     

Composition dependent phase connectivity, dielectric and magnetoelectric properties of magnetoelectric composites with Pb(Mg1/3Nb2/3)0.67Ti0.33O3 as piezoelectric phase

Ferrite (Ni_0.6Co_0.4Fe₂O₄) phase, ferroelectric (Pb(Mg_1/3Nb_2/3)_0.67Ti_0.33O₃) phase and magnetoelectric composites of (x)Ni_0.6Co_0.4Fe₂O₄ + (1 − x)Pb(Mg_1/3Nb_2/3)_0.67Ti_0.33O₃ with x = 0.15, 0.30 and 0.45 were prepared using solid-state reaction technique. Presence of Ni_0.6Co_0.4Fe₂O₄ and Pb(Mg_1/3Nb_2/3)_0.67Ti_0.33O₃ was confirmed using X-ray diffraction technique. The scanning electron microscopic images were used to study the microstructure of the composites. Connectivity scheme present in the magnetoelectric (ME) composites are discussed from the microscopic images. Variation of dielectric constant and dielectric loss with temperature for all the composites was studied. Here we report the effect of Ni_0.6Co_0.4Fe₂O₄ mole fraction on connectivity schemes between Ni_0.6Co_0.4Fe₂O₄ and Pb(Mg_1/3Nb_2/3)_0.67Ti_0.33O₃ composite. The variation of magnetoelectric voltage coefficient with dc magnetic field shows peak behaviour. The maximum value of magnetoelectric voltage coefficient of 9.47 mV/cm Oe was obtained for 0.15Ni_0.6Co_0.4Fe₂O₄ + 0.85Pb(Mg_1/3Nb_2/3)_0.67Ti_0.33O₃ composites. Finally we have co-related the effect of Ni_0.6Co_0.4Fe₂O₄ content and dielectric properties on magnetoelectric voltage coefficient.     

Microstructure, domain structures and ferroelectric properties in (Pb0.8,La0.1,Ca0.1)TiO3/Pb(Zr0.2,Ti0.8)O3 bilayered thin film

Ferroelectric (Pb_0.8,La_0.1,Ca_0.1)TiO₃/Pb(Zr_0.2,Ti_0.8)O₃ (PLCT/PZT) bilayered thin film was prepared on Pt(111)/Ti/SiO₂/Si(100) substrate by RF magnetron sputtering technique. Pure perovskite crystalline phase, determined by X-ray diffraction, was formed in the PLCT/PZT bilayer. The bilayered film exhibited a very dense and smooth surface morphology with a uniform grain size distribution. The ferroelectric domain structures were investigated by a combination of vertical and lateral piezoresponse force microscopy (VPFM and LPFM, respectively). It is demonstrated by both VPFM and LPFM observations that out-of-plane and in-plane lamellar ferroelectric domains coexist in the bilayered thin film. The PLCT/PZT bilayered film possesses good ferroelectric properties with relatively high spontaneous polarization (2P_s = 82 µC/cm²) and remnant polarization (2P_r = 26.2 µC/cm²).     

Effect of the level of the addition of Pb(Y0.5Nb0.5)O3 on the structure, microstructure and ferroelectric properties of PZT(53/47)

In this work an attempt is made to study [Pb(Zr_0.53Ti_0.47O₃)O₃]_1-X-[Pb(Y_0.5Nb_0.5)O₃]_X system with x = 0.0125, 0.025, 0.05, 0.075 and 0.1. It was shown that there is limited solid solubility (2.5 mol%) of Pb(Y_0.5Nb_0.5)O₃ (PYN) in PZT (53/47). The substitution of PYN gave rise to the reduction of the volume of PZT’s unit cell. For the samples doped above this level of PYN, an extra phase comprising of Y³⁺, Zr⁴⁺ and Ti⁴⁺ cations were detected based on EDS-SEM and XRD analysis and also a structural shift towards a rhombohedral phase was noticed for the main PZT phase. Further, the addition of PYN up to 2.5 mol% was seen to increase the room temperature relative permittivity and d₃₃ parameter. However, these parameters declined for the samples substituted with more than 2.5 mol% PYN due to the formation of non ferroelectric extra phase.