In this paper, we have reported a conformable PbTiO3 ceramics doped with Ni by standard double sintering technique as well as chemical co-precipitation method which were successfully synthesized by means of carefully controlled processing parameters. Single phase formation was confirmed through X-Ray Diffraction (XRD) analysis, IR spectroscopy, SEM micrograph and TEM images. Discussion and comparison between both preparation methods were made on the basis of observed results. The tetragonality c/a decreased from 1.049 to 1.0276 for ceramic samples and decreased from 1.06519 to 1.0365 for co-precipitation samples by increasing Ni content. TEM images show small ferroelectric domains of about 3 to 14 nm for the co-precipitation sample and 26 to 48 nm for the ceramic samples. The SEM of co- precipitation samples shows that the microstructure is very dense. The behavior of ε identifies that our samples are nonrelaxor. Increasing the Ni concentration increases the value of dielectric constant and the Tc is shifted to lower temperature.
Lead titanate, PbTiO3 ceramic, is a powerful piezoelectric material for high tempera- ture and high frequency applications such as infrared sensors and capacitors. It is very difficult to obtain a pure and dense PbTiO3 phase at a maximum c/a ratio. The influences of doping Ni, Nb and Mn on structural electrical and electromechanical properties of lead titanate were investigated. The anisotropy decreases with increasing amount of dopants [
The small amount of Ca changes the electrical conductivity and the transition temperature Tc of ferroelectric phase. The XRD and SEM analysis shows the increase of grain and particle size with the increase of Ca. The dc conductivity of lead titanate doped with Ca is influenced by Ca content at room temperature and near transition temperature. The Tc temperature shifts to lower values by increasing Ca addition [
The electrical and microstructure properties of piezoelectric ceramic system (BiYbO3-PbTiO3)-(PbZnNb)O3 were reported. The system had a perovskite structure with a tetragonal phase by increasing PZN, the tetragonality (c/a) decreased the mechanical coupling factor and piezoelectric properties of the samples were improved, which might be attributed to the improved density structural stability and homogeneity [
A ternary system of PNZT has been prepared by conventional mixed oxide. The formation of the perovskite phase is established by X-ray diffraction analysis; SEM confirms what we found by X-ray analysis. Dielectric properties like dielectric constant and dielectric loss (ε0 and tanδ) indicate poly-dispersive nature of the material. The temperature dependent dielectric constant (ε0) curve indicates relaxor behavior with two dielectric anomalies. The poly-dispersive nature of the material is analyzed by Cole-Cole plots. The activation energy follows the Arrhenius law and is found to decrease with increasing frequency for each composition. The frequency dependence of ac conductivity follows the universal power law. The ac conductivity analysis suggests that hopping of charge carriers among the localized sites is responsible for electrical conduction. The ferroelectric studies reveal that these ternary systems are soft ferroelectric [
The objective of the present work is to improve the physical and piezoelectric properties of PbTiO3 by the addition of Ni ions and to prepare the PbTiO3 by different methods to make a comparison between the ceramics and co-precipitation samples.
First series perovskite Pb1-x NixTiO3, x = (0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) has been prepared using a conventional ceramic process. The oxides were exposed to 800˚C as presintered temperature. The crushed mass was grinded and pressed as disks at 5000 kg /cm2 and sintered at 1200˚C for 2 hours then left to be cooled gradually with the rate 50˚C/hr. The co-precipitation procedure were used to prepare the other series of Pb1-xNixTiO3 (x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5). The chemical reagents were Titanium chloride (TiCl3・15H2O), Nickel (II) chloride (NiCl2・6H2O), Lead chloride (PbCl2) and sodium hydroxide (NaOH). All the chemical reagents were dissolved into 200 ml of distilled water. After mixing and stirring solutions for 6 hours, chemical precipitation was achieved at room temperature vigorous stirring by adding of NaOH solution gradually. The reaction system was kept at 80˚C for 2 hours and PH solution ±12. After the system cooled to room temperature, the precipitates were washed with distilled water until PH-7. Finally the samples dried in oven at 200˚C for several hours and sintered at 1000˚C for 2 hours then left to be cooled gradually with the rate 50˚C/hr.
The samples were examined by x-ray diffraction using a Philips model (PW-1729) diffractometer. IR spectra for the prepared samples were carried out at room temperature using the Perkin-Elmer-1430 recording infrared spectrophotometer in the range from 200 cm−1 to 5000 cm−1. As for the Scanning Electron Microscope of samples, we used SEM Model Quanta 250 FEG (Field Emission Gun) attached with EDX Unit (Energy Dispersive X-ray) Analyses. We used TEM model (Transmission Electron Microscope JEOL-100SX) and HRTEM model (High Resolution Transmission Electron Microscope JEOL EM 2-100). The dielectric measurements were performed using RLC bridge type 815 B. The prepared tablets with silver electrodes were heated with heating rate 4˚C /min; the temperature was controlled by a thermocouple contacting the samples holder near where the sample was situated.
The XRD patterns for ceramic and co-precipitation samples of Pb1-xNixTiO3 which (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) are shown in
The patterns correspond well to PbTiO3 phase with a typical tetragonal symmetry showing splitted (001/100), (101/110), (002/200) and (112/211) peaks. When Ni content increases, no change for the patterns is observed, whereas the other phases of Ni previously mentioned and PbO disappeared with increasing Ni content and the two peaks in each group of the tetragonal phase patterns approached to each other, indicating decrease in tetragonality. This phenomenon is observed from XRD patterns from the decreasing of the ratio c/a. The appearance of pre-mentioned diffraction peaks demonstrates that the perovskite nano crystallites of PbTiO3 can be formed successfully at 600˚C [
The XRD pattern prove that a single which tetragonal phase was obtained for all compositions with different Ni content with a = 4˚A, c = 3.875˚A and c/a = 0.96875, the crystallite size was determined from the line width using Scherer's equation. It is noticed that the samples with low value line width has higher crystallite size as given in
Co-precipitation samples | ||||
---|---|---|---|---|
(112/211) | (002/200) | (101/110) | (001/100) | X |
1.89 | 2.96 | 0.98 | 1.4 | 0.0 |
1.7 | 2.3 | 0.88 | 1.26 | 0.1 |
1.66 | 2.33 | 0.72 | 1.22 | 0.2 |
1.49 | 2.16 | 0.69 | 1.04 | 0.3 |
1.41 | 2.3 | 0.66 | 0.93 | 0.4 |
1.28 | 2.14 | 0.34 | 0.43 | 0.5 |
Ceramic samples | ||||
(112/211) | (002/200) | (101/110) | (001/100) | X |
1.87 | 2.94 | 0.98 | 1.34 | 0.0 |
1.71 | 2.31 | 0.87 | 1.26 | 0.1 |
1.64 | 2.34 | 0.71 | 1.21 | 0.2 |
1.49 | 2.18 | 0.67 | 1.02 | 0.3 |
1.4 | 2.35 | 0.64 | 0.91 | 0.4 |
1.26 | 2.15 | 0.31 | 0.42 | 0.5 |
between the crystallite size and the peak width which widely discussed and reported on PT ceramics [
The influence of Ni content on the lattice constant of the prepared materials is shown in
The variation of lattice parameter (a) and (c) by increasing Ni content has low values for co-precipitation sample than the ceramic sample. Although the ionic radius of Ni2+ is smaller than the Pb2+ ionic radius the lattice parameter (a) increase by increasing Ni concentration which is related to the increase of internal strain which cause the lattice to expand in the (a) direction. The decrease of the lattice parameter (c) by increasing Ni content may be due to the low value of the Ni2+ ionic radius compared with ionic radius of Pb2+.
The PbTiO3 doped with Ni are exposed to annealing process at 600˚C, 800˚C and 1000˚C for 2hours to ensure complete crystallization and remove of any foreign phases.
X | Particle size (nm) | ||
---|---|---|---|
600˚C | 800˚C | 1000˚C | |
0.0 | 25.561 | 21.266 | 28.417 |
0.1 | 15.214 | 20.835 | 27.044 |
0.2 | 19.413 | 16.547 | 20.478 |
0.3 | 23.538 | 19.111 | 20.435 |
0.4 | 25.096 | 17.712 | 18.905 |
0.5 | 20.442 | 17.708 | 18.649 |
Co-precipitation | x-ray | 28.417 | 27.044 | 20.478 | 20.435 | 18.905 | 18.649 |
---|---|---|---|---|---|---|---|
TEM | 14.47 | 13.395 | 11.56 | 7.835 | 4.67 | 3.244 | |
Ceramics | x-ray | 60.356 | 55.337 | 44.274 | 42.170 | 37.959 | 35.920 |
TEM | 48.966 | -------- | -------- | ------- | -------- | 25.629 |
From
co-precipitation method smaller than that of prepared by ceramic method. The crystallite size derived from XRD has higher value than that derived from TEM since. The XRD is a bulk technical and the crystallites lower than 20 nm are too low to be detected carefully by X-ray.
IR spectra carried out in lead titanate doped with Ni prepared by both ceramic and co-precipitation methods are shown in
The wide band appearing at 377, 573 cm−1 corresponds to vibrational frequency of Ni-O bond at tetrahedral and octahedral coordination. We can say that the peak appeared around 1400 - 1600 is attributed to the symmetrical H-O-H and as symmetrical H-O-H bond vibration these results are confirmed with the pervious reported data [
The absorption peak at 500 (υ2) which due to M-O bond shifted to lower frequency from 573 to 553 cm−1 which confirming the formation of more perovskite phase at higher Ni concentration. The band near 573 cm−1 is associated to octahedral bond and indicates the formation of a perovskite phase.
In conclusion the studies of IR spectroscopy confirm the formation of a perovskite structure.
Correlating the micrometer grain size reviled by SEM with the nanometer size of the ferroelectric domain determined by XRD and TEM images one can conclude that ceramic grains have multi domain structure [
The Pb1-xNixTiO3 powder for ceramic and co-precipitation samples treated at 1200˚C and 1000˚C respectively were subjected to TEM microstructure analysis to determine the average particle size.
an average particle size ranged from 14.47 to 3.244 nm for co-precipitation samples. There is some agglomeration appears for ceramic sample at some location. Also TEM images show small ferroelectric domains of about 3 to 14 nm for the co-precipitation sample and 26 to 48 nm for the ceramic samples as given in
Samples | X | 0.0 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 |
---|---|---|---|---|---|---|---|
Co-precipitation at 1000˚C | Gd (nm) | 167.76 | 139 | 82.26 | 76.56 | 74.306 | 66.22 |
Ceramics at 1200˚C | Gd (μm) | 3.3794 | 0.9237 | ------ | 0.7428 | ---- | 0.740057 |
The crystallite size derived from XRD has higher value than that derived from TEM since. The XRD is a bulk technical and the crystallites lower than 20 nm are too low to be detected carefully by X-ray. For the sample x = 0.5 the identification of d spacing d = 0.13nm suggest the tetragonal crystallite as shown in Figure11 corresponding to 212 plane of PbTiO3 phase [
The samples have a first order phase transition from tetragonal to cubic phase at certain curie temperature Tc. The material converted from ferroelectric to Para electric state. The variation of curie temperature Tc and the value of dielectric constant are shown in the
It is clearly depicted that all the dielectric constant show a distinct phase transition point characterized by narrow curie peak, Which may be due to the absence of heterogeneity [
The XRD patterns contain single phase, PbTiO3 phase. Around 2θ = 31.46 splitted peak (001/100) is observed, indicating the presence of tetragonal phase. The studies of IR spectroscopy confirm the formation of a perovskite structure. The PbTiO3 powder derived from ceramic method consists of particles with grain size ranged from 3.3 to 0.7 μm. The SEM of co-precipitation samples shows that the microstructure is very dense. The variation of the grain size of both samples as a function of Ni content showed a decrease in grain size where the grain size for co-precipitation samples ranged from 167.76 to 66.22 nm. The TEM images show small ferroelectric crystallite size about 14 to 3 nm for the co-precipitation samples and from 48 to 26 nm for the ceramic samples. The dielectric constant is increased by increasing temperature, but is nearly independent of frequency. The behavior of ε identifies that our samples are non-relaxor. Increasing the Ni concentration increases the value of dielectric constant and the Tc is shifted to lower temperature.
Tawfik, A., Hemeda, O.M., Hemeda, D.M., Barakat, M. and Shady, R. (2016) Structural Morphological and Dielectric Properties of Pb1-xNixTiO3 Doped with Ni. Open Journal of Applied Sciences, 6, 796-813. http://dx.doi.org/10.4236/ojapps.2016.611070