Structural and mechanical properties characterization of barium strontium titanate (BST) ceramics

Ba_(1-x)Sr_(x)TiO₃ ceramics, where x?=?0.05, 0.10, 0.15, and 0.20, were prepared by solid state reaction technique. X-ray diffraction analysis confirmed the formation of single phase perovskite structures. Mechanical properties such as ultrasonic attenuation, longitudinal wave velocity, and longitudinal elastic modulus were studied by an ultrasonic pulse echo technique at 2 MHz. Investigations of ceramic microstructures and mechanical properties showed its dependence on composition and sintering time. Increasing of Sr content, x, resulted in a decrease in bulk density and ultrasonic attenuation and an increase in velocity and modulus. Also, size of crystallites and c/a ratio were found to decrease with increasing of x, and increased with increasing of sintering time. High temperature ultrasonic studies showed, in addition to Curie phase transition, two relaxation peaks and its origin was investigated. The acquired structural and mechanical results were correlated and discussed.     

Peculiarities of Variation of the Dielectric Permittivity and the Pyroelectric Coefficient with Temperature in PZT-Based Ferrosoft Ceramics Modified with Different Additives of PbGeO3

ABSTRACT

The temperature dependencies of the dielectric permittivity ?( T) the dynamic pyroelectric coefficient γ_d( T) and the quasi-static pyroelectric coefficient γ_st( T) of prepoled samples of the low-coercive materials belonging to the PZT-based multicomponent system modified with 0.5%; 1% and 2% PbGeO₃ and having the Curie temperatures T _c = 207, 215 and 206°C, respectively, were studied. Polarization of the samples was performed under three different conditions. It was been established that in the ?( T) curve one can observe a step-like variation of ?( T) or a slope variation at temperatures below the temperature maximum by 40–50°C. The additional low- and high-temperature maxima are observed in the γ_d( T) and γ_st( T) curves.     

Mechanical and electric fatigue of PZT(53/47) films on metallic substrates

Abstract

We have investigated the fatigue of electromechanical and dielectric properties of sol-gel derived PZT(53/47) thin films deposited on metallic substrates by means of electric and mechanical cycling. For the mechanical cycling a two point bending method was used to apply transversal stress to the samples. During mechanical cycling the piezoelectric coefficient d₃₁ remained constant up to about 10⁵ cycles, for a higher number of cycles a strong decrease was observed. During electric cycling no significant changes in the ferroelectric and electromechanical hysteresis loops could be found up to about 3×10⁵ cycles. Above this number the coercive field increases, the maximum strain and the remanent polarization decrease.

Obviously each electric cycling of the investigated films is accompanied by a mechanical cycling. It is assumed, that microcracks induced by mechanical stress are the main reason for the deterioration of the physical properties films during electric and mechanical cycling both.     

Study on properties of Al2O3 whisker reinforced PZT95/5 type ferroelectric transitional ceramics

Abstract

9 Al₂O₃·2B₂O₃ whisker was used to reinforce PZT95/5 type ferroelectric transitional ceramics. The relation between properties (including electric and mechanical properties) and whisker content was studied. Experiment results indicate: Composites with proper whisker content can keep electric properties almost as good as that of base material, while improve mechanical properties effectively. Whisker pulling and bridging play important roles in the process of reinforcing.     

STOICHIOMETRIC STUDY OF ARCMELTED Tb(x)Dy(1 − x)Fe2 FOR PASSIVE DAMPING

ABSTRACT

Energy absorption properties of offstoichiometric Terfenol-D (Tb_(x)Dy_{(1 ? x)}Fe₂) arcmelted rods were experimentally measured. Samples with Tb compositions for x = 0.35, 0.40, 0.45, 0.50, 0.75 and 1.0 were tested in compression using an MTS load frame under various constant magnetic field conditions. The peak energy absorption occurs at a stress amplitude of 20 MPa for 0.30 ≤ x ≤ 0.50 and shifts to 40 MPa for the Tb compositions of x = 0.75 and 1.0. Combined magnetomechanical loading revealed the influence of magnetic field associated with energy absorption properties. The energy absorption is shown to increase with increasing Tb composition up to x = 0.5.     

Chemical processing and properties of Sr2(Ta,Nb)2O7 thin films

Abstract

The crystallographic orientation, microstructure and electrical properties of Sr₂(Ta, Nb)₂O₇ thin films strongly depended on the composition (Ta:Nb). Post-annealing at 850°C was effective for the improvement of some properties. The thin films with relatively Nb-rich compositions, such as Sr₂(Ta_0.6Nb_0.4)₂O₇ and Sr₂(Ta_0.5Nb_0.5)₂O₇, showed the (0k0) preferred orientation. The Sr₂(Ta_0.5Nb_0.5)₂O₇ thin film had a lamination layer structure after the post-annealing at 850°C for 6 min in oxygen. The characteristic microstructure originated in the crystallographic orientation of (0k0), which is the cleavage plane, and influenced electrical properties. The dielectric constant little change with the composition, however, the P-E hysteresis properties improved with the Nb content.     

Structure property relations of BST thin films

Abstract

We report on the properties of thin BST films which were grown in a planetary multi-wafer MOCVD reactor which handles 5 six inch wafers simultaneously. The reactor is combined with a liquid delivery system which mixes the liquid precursors from three different sources: 0.35 molar solutions of Ba(thd)₂ and Sr(thd)₂ and a 0.4 molar solution of Ti(O-i-Pr)₂(thd)₂. Film growth on strongly (111)-textured Pt substrates is investigated within a wide parameter field. We focus on the properties of films with the composition Ba_0.7Sr_0.3TiO₃ and thickness between 10 and 130 nm. Topics to be discussed include: the change of the texture of the BST films, which is (100) for deposition temperatures above 600°C and changes to a random orientation at lower temperature, and a comparison of planar films with films on structured substrates. The electrical properties, e.g., permittivity and leakage current, are discussed in relation to the microstructure.     

Low temperature synthesis and structural,dielectric and optical studies of Bi1−xGdxFeO3 (x = 0, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15) nanoceramics

Abstract

Gd-substituted BiFeO₃ (BFO) multiferroic nanoceramics with the compositional formula Bi_1-xGd_xFeO₃ (x?=?0, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15) were prepared by low temperature sol gel method. Phase identification of all the samples were carried out using XRD analysis. FTIR analyses showed the presence of stretching and bending vibrations of various bonds present in all the samples. Dielectric properties such as dielectric constant and dielectric loss were measured as a function of frequency and Gd concentration, wherein the enhanced dielectric properties were observed with the addition of Gd dopant. The optical absorbance spectra of all the samples were measured and the energy band gaps (E_g) were obtained from Tauc plot. Explanation of the observed results was discussed and various possible applications in real multiferroic systems were highlighted.     

Effects of temperature on the ferroelectric properties of PbZr0.53Ti0.53O3-based capacitors prepared by pulsed laser-ablation deposition

Abstract

The effects of elevated temperature on the long and short term ferroelectric properties of La_0.5Sr_0.5Co₃(LSCO)/PbZr_0.53 Ti_0.47O₃(PZT)/La_0.5Co₃(LSCO) heterostructure capacitors are presented in this paper. Capacitors are evaluated in the temperature range of 25°C to 100°C. Polarization values (switched and non-switched), coercive voltages, and PZT resistivity are measured as a function of temperature. Rate of fatigue, tendency to imprint, and retention loss are also investigated in the 25–100°C temperature range. An activation energy for the process responsible for loss of remanent polarization is determined from the fatigue data.     

Characterization of BaTiO3—BaZrO3 Solid Solution Thin Films Prepared by MOCVD

Thin films of the solid solution system Ba(Ti_{1 ? y} Zr _y )O₃ (y = 0, 0.37, 1) have been grown on ?111? Pt-coated silicon substrates by means of metal-organic chemical vapor deposition (MOCVD). Commercially available liquid precursors typical for the fabrication of perovskite thin films were used: Ba(thd)₂(diethylene-triamine), Ti(OⁱPr)₂(thd)₂, and Zr(OⁱPr)₂(thd)₂ (thd = C₁₁H₁₉O₂) dissolved in diglyme (C₆H₁₄O₃). Growth took place in a horizontal type reactor (AIX-200). The vaporizer technology based on a TriJet? liquid delivery system provided by AIXTRON. It allows to feed in four metal-organic species in a pulsed injection mode. We combined process-related studies (growth rate, rate-limiting factors) with material-related properties (crystallinity and morphology) using various analytical techniques (X-ray analysis, scanning electron microscopy). Furthermore we characterized the samples electrically with respect to the voltage dependence of permittivity and dielectric losses.     

Effects of Oxide Additives Coating on Microstructure and Dielectric Properties of BaTiO3

Effects of mixing methods (mechanical mixing, chemical coating) on microstructure and dielectric properties of Ho, Mg and Mn doped BaTiO₃ have been studied. BaTiO₃ particles coated with Ho, Mn and Mg were prepared by a homogeneous precipitation method using urea, and then silica was coated by the sol-gel technique. The adsorption of additives on the BaTiO₃ surface was confirmed. Temperature characteristics of capacitance were satisfied by mechanical mixing and chemical coating techniques, both of which yield different sintering and microstructure behaviors. Pyrochlore phase (Ho₂Ti₂O₇) was observed on the mechanically mixed sample, whereas none of pyrochlore phase was observed at the coated sample after thermal etching. Those different behaviors caused by the degree of homogeneous distribution of the additives in BaTiO₃ matrix were confirmed by EDS analysis.     

Excimer laser ablation processed ferroelectric and antiferroelectric thin films

Abstract

The dielectric and electrical properties of excimer laser ablated processed paraelectric (Ba_0.5, Sr_0.5)TiO₃, ferroelectric Bi-layered SrBi₂(Ta_0.5Nb_0.5)₂O₉, and antiferroelectric (PbZrO₃) thin films have been investigated. The effect of processing parameters on the microstructure of the films and the functional properties has been presented in detail. Some of the recent studies of stress induced effects, dielectric, hysteresis and ac and dc electrical properties have been highlighted in conjunction with microstructures of the films.     

Dispersion and Optical Activities of Copper (II) Metal Oxide Nanoparticles with Polyethylene Glycol in Aqueous Medium Studied with Physicochemical Properties and UV-Vis Spectrophotometry

Abstract

Copper (II) oxide nanoparticles are considered to be transition metal oxide having unique properties and could be useful in biochemical and biomedical applications. The hydrophilic biocompatible polyethylene glycols (PEG) were used for dispersion of CuO in aqueous medium. The physicochemical properties (PCPs) and absorbance were determined for CuO dispersed. The PCPs and optical data showed a maximum CuO dispersion with water and PEG which revealed that the impact of the hydrophobic chain and hydrophilic [sbond]OH groups in PEG on dispersion activities The results can provide new insights in the development of dispersion activities of CuO with PEG _{(400 and 6000).}     

Studies about Microstructures and Mechanical Properties of Ti(C,N) Ceramic Material Using Different Solvents

Abstract

Ti(C,N) ceramic materail plays an important role in the field of material processing due to their good mechanical properties and thermal stability. In this experiment, Ti(C,N) powders were successfully prepared by solvothermal and high-temperature calcining method, using TiOSO₄ and C₃H₆N₆ as raw material, and n-propanol and ethylene glycol as solvents. The microstructure of Ti(C,N) powders were characterized by X-ray diffraction and field emission scanning electron microscope, and their hardness were tested by vickers microhardness tester. The microstructure and mechanical properties of Ti(C,N) powders using two different solvents were investigated comparatively. Ti(C,N) powders prepared using n-propanol with a size of about 20–30?μm can reach the maximum hardness of 660 HV after sintering. Ti(C,N) powders prepared using ethylene glycol with size range of 3?μm to 5?μm come up to the maximum hardness of 889 HV. The different mechanism of solvents in preparation of Ti(C,N) ceramic material was discussed.     

Effects of Ultrasonic Treatment and Nanoparticles Addition on Microstructure and Mechanical Properties of AS41A Magnesium Alloy

Abstract

TiB₂ nanoparticles reinforced AS41A alloys were fabricated by ultrasonic assisted stir casting. The influence of ultrasonic treatment and TiB₂ nanoparticles on the microstructure and mechanical properties of AS41A magnesium alloy was investigated. The results showed that the ultrasonic treatment obviously refined microstructure, thereby improving the mechanical properties of the magnesium alloys. The addition of TiB₂ further increased the tensile strength slightly while maintaining the improved elongation as the ultrasound-treated matrix alloys.The ultimate tensile strength, yield strength and elongation of the obtained nanocomposites were improved by 27.4%, 43.5% and 84.6% compared with those of the as-cast matrix alloys, respectively.     

Effect of the firing temperatures on the phase formation,microstructure and electrical properties of BaTi0.91 Sn0.09O3 ceramics synthesized via the solid state combustion method

Abstract

BaTi_0.91Sn_0.09O₃ (BTS) ceramics were synthesized by the solid state combustion method with glycine as the reducting agent and metal nitrates as the oxidants. The calcination and sintering temperatures were in the range of 1200?°C–1300?°C and 1300?°C–1450?°C, respectively, for 2?h. Pure perovskite powders were obtained from the samples calcined at ≥1275?°C for 2?h. The crystal size calculated by Scherrer equation was in the range of 22–30?nm. XRD results of the sintered ceramics showed the coexistence of the tetragonal (T) and orthorhombic (O) phases in all samples, and were confirmed by Rietveld refinement. The grain sizes increased from 9.04 to 29.83 µm when the sintering temperatures increased from 1300?°C–1450?°C for 2?h. The highest density (5.95?g?cm^?3), large piezoelectric strain (d₃₃* = 830?pm/V) and best dielectric constant (ε_r = 14841) were obtained from the sample sintered at 1350?°C for 2?h. This study clearly demonstrates the potential of the solid state combustion method for producing high density and good dielectric properties in BTS ceramics.     

Study of the structure and electrical properties of PMN-PNN-PT ceramics near the morphotropic phase boundary

A series of Pb(Mg_1/3Nb_2/3)O₃-Pb(Ni_1/3Nb_2/3)-O₃-PbTiO₃ (PMN-PNN-PT) ceramics with compositions of (1–x)(0.67PMN-0.33PT)-x(0.64PNN-0.36PT) (x = 0.1–0.9) were synthesized using the columbite precursor method. The phase structures, as well as the dielectric and piezoelectric properties of the ceramics were investigated in detail. X-ray diffraction results demonstrate that all the samples possess a pure perovskite structure. It is found that the morphotropic phase boundary (MPB) region of the PMN-PNN-PT ternary system is located near the line connecting the MPBs of the PMN-PT and PNN-PT binary systems. A high value of the maximum dielectric constant (ɛ_m = 45540, at 1 kHz), together with a high value of the piezoelectric coefficient (d₃₃ = 780 pC/N), were obtained for the composition x = 0.2. The results show that a partial substitution of PNN-PT for PMN-PT can lead to improved electrical properties in this ternary system.     

White-Light-Emitting Single Component Metal-Organic Frameworks Based on 2,3-Pyridinedicarboxylic Acid

Abstract

Two white-light-emitting MOFs, [Dy(pydc)·(H₂O)₂]·DMF_0.66 (1) and [Gd_1.9Dy_0.1(pydc)_1.5(H₂O)₃]·DMF_1.5?C460 (2), were synthesized by the reaction of a rigid ligands H₂pydc (H₂pydc = 2,3-pyridinedicarboxylic acid) and Dy(III) ions under solvothermal conditions. The emission color of compound 1 is tunable by variation of excitation light to get yellow-to-white photoluminescence. When proportion of Dy³⁺ and H₂pydc is 1:3 could obtain the single component compound 1 with CIE coordinates of (0.2935, 0.3335), which is close to (0.3333, 0.3333) of the pure white light. To investigate the matrixes effect and luminescent dye C460@MOF, Gd(III) ions and C460 were introduced to form MOFs 2 with the mixed metal centers. When concentration of C460 is 10^?3 mol/L, MOFs 2 shows CIE coordinates of (0.3255, 0.3452). This work provides a practical strategy for the development of white-light emitting phosphor based on single component MOFs, which opens a new region for WLEDs.     

DRIVING CHARACTERISTICS OF ULTRASONIC NOZZLE USING PSN-PMN-PZT CERAMICS

ABSTRACT

In this paper, ultrasonic nozzle and driving circuit were manufactured and their electrical properties were investigated. Ultrasonic nozzle was fabricated using Pb[(Sb_1/2Nb_1/2)_0.035(Mn_1/3Nb_2/3)_0.065(Zr_0.49Ti_0.51)_0.90]O₃+ 0.5wt%PbO (abbreviated as PSN-PMN-PZT) ceramics showing excellent piezoelectric characteristics. In order to drive ultrasonic nozzle, Pulse Width Modulation controller (abbreviated as PWM) of KA3525A was used. With increasing the input voltage of nozzle, average diameter of fuel oil droplet was increased up to 16 V and then decreased. At the input voltage of 12 V, volume average diameter of fuel oil droplet showed the minimum value of 37.3 μm and also at the input voltage of 16 V, volume average diameter of fuel oil droplet showed the maximum value of 51.3 μm.     

Investigation on structural and electrical properties of BZT ceramics synthesized at low temperature

Abstract

Due to environmental concerns, lead free ceramics such as KNN- NBT and BT have growing interest in applications such as actuators and sensors. Among them Barium Zirconate Titanate (BZT) has become most attractive because it is derived from two perovskite lattice i.e. Barium Titanate (BaTiO₃) and Barium Zirconate (BaZrO₃). It has been reported that Zirconium substitution in titanium lattice enhances the material properties. In the present paper BZT was prepared using solid state route. By adding a mixture of Li₂CO₃ as a sintering aid, the sample could be sintered at 1150?°C having around 94% of the theoretical density. Prepared samples were then subjected to XRD analysis. X-ray diffraction revealed the formation of single phase material. It is observed that the electrical properties of such low-temperature sintered samples are comparable with BZT samples prepared via conventional sintering at a high temperature. It is also observed that the curie temperature shift towards room temperature for a samples sintered at low temperature.