1
Elaboration and characterization of a piezoelectric ceramic resonator
A.Khiat*1-2, M.Kadri2, S.Hamzaoui2
1Research Center in Industrial Technologies CRTI Cheraga 1P.O. Box 64 Cheraga 1604 Algeries, Algeria
*m.khiat@csc.dz
2Laboratory of Electron Microscopy and Materials Science (LMESM) BP 1505 El Mnaouer, UST-MB, Oran, Algeria.
Abstract— In this work. We Synthesized PbTiO3
from PbO and TiO2oxides from Solid state reaction and we studied the development and manufacture of solid piezoelctrique resonator of PT .We played on parameter as sintering time. We used XRD and SEM for morphological characterization and Analyzer for impedance piezoelectric characterization.
.
Keywords—PT; ferroelectric; resonator; impedance; XRD;
SEM.
I. INTRODUCTION
Lead titanate (PbTiO3) is a classical ferroelectric material, which possesses excellent dielectric, piezoelectric and pyroelectric properts and belongs to the ABO3 perovskite group, having tetragonal structure at room temperature, Among all the members of the perovskite family lead titanate has the highest tetragonal distortion (c/a ∼ 1.064) which makes it remarkable over others. This tetragonal distortion corresponds to the highest spontaneous polarization (Ps) among all the ferroelectric perovskites.
The spontaneous polarization (Ps) and pyroelectric coefficient of thin films of PbTiO3have been reported to be as high as 86μC/cm2 and 250μC cm−2 K−1, respectively, with low room temperature dielectric constant εr∼ 150 as compared to those of other thin-film ferroelectric materials under investigation[1].it has a high Curie temperature (490
◦C)[2].The primary hurdle in PT fabrication is the synthesis of a single phase with the required perovskite structure. The difficulty is due to the volatility of PbO at elevated temperatures. The PbTiO3structure can only tolerate minor amounts of Pb-loss, higher levels of which effectively promote second phase formation and the degradation of piezoelectric properties. An example is the formation of a PT phase with the pyrochlore structure observed during a co-precipitation synthesis experiment. A more common occurrence is the formation of a two-phase mixture with TiO2 .The volatilization of PbO is known to increase markedly at temperatures above 8000C, though the critical temperature is debated. Kim et al. have stated that a PbO rich PT will form a liquid phase above 8380C, Alguero et al [3].The operational frequency range varies greatly depending on the applications. For example, common
frequencies of 2–10 MHz are used in nondestructive testing and evaluation to locate flaws in materials, but lower frequencies can also be used to inspect low density materials. Medical diagnostic transducers generally operate in the frequency range of 2–18 MHz, though frequencies up to 50–100 MHz have been used for intravascular, ophthalmic, skin imaging and small animal imaging. The useful spectrum of underwater acoustic extends from sub- audible and audible frequencies allowing for great distances (one to several kilometers) to ultrasonic frequencies (up to
>1 MHz) where echo distances are shorter and increased accuracy of distance measurements is desirable . Applications over this wide frequency range require numerous transducer designs. A number of geometries have been demonstrated, resulting in effective underwater acoustic transducers[4].
II. EXPERIMENTAL
The reactant powders were commercially available PbO (99% purity), and TiO2 (anatase form, 99% purity).
Stoichiometric quantities were weighed to form PT, and these were placed in a agate mortar hand after 1h of milling.
Milled powders for the sintering experiments were loaded into a die and uniaxially pressing at approximately 100MPa.
Samples were placed in an alumina crucible, sintered for 12 h in air at 700?C,
Powder was uniaxially pressed in a 10mm die at 55MPa and sintered in an oven at 11000C with several time 1h,8h and 24 h.samples were heated at 5?C/min to the selected maximum temperature. The surfaces of the pellets were removed prior to XRD pattern collection by gently grinding with 400-grit SiC emery paper so that excess surface PbO was removed.
Characterization
Morphology, size of PT nanoparticls were characterized by scanning electron microscope (SEM) JEOL (JSM 6610LA).The structures PT were examined using XRD, powder X-ray diffraction. The used of impedance Analyzer Agilent thecnologis E5071C (9KHz – 8.5GHz) for
resonance frequencies
2 III. RESULTS ANDDISCUSSIONS
Structural Study of PT
The physical condition of the sintered ceramics varied as a function of time. Samples sintered at 1h, 8h, and 24h were monolithic and relatively robust.
Sample X-ray diffraction patterns were same, unless there is a crystallization of PbO in the c pattern. The peak at 2θ = 31.33 ° was used to estimate the Ф particle size (nm), the Scherrer relationship from the mid-height width of the X- ray diffraction peak relationship
Ф(nm)= β .
( θ) θ
Where β (2θ) is the width at half height of the peak, expressed in radians, λ is the wavelength of X-rays used (λ(KαCu)= 1.54056 Å) and θ the angle of diffraction.
20 40 60
0 1000 2000 3000
: PbTiO3
PbO tetragonal
Intensity(UA)
2degrees)
(c) 24h
(b) 8h
(a) 1h
Fig 1. (a,b,c) XRD patterns of PT compact at 55MPa, sintered at 11000C with several time 1h,8h and 24 h.
Results of the Rietveld analyses of XRD patterns from the samples sintered at various time are presented in Table 1 . Some interesting trends were revealed:
-The unit cell dimensions are not significantly influenced by the sintering time. The c/a ratio increases from 1.051 to 1.054.
-Crystallite size increases from 32.3 Å to 34.2 nm.
-Density increases from 6.61 gcm-3to 6.22 gcm-3. Table 1 Crystallite, density and size lattice parameters c/a ratio.
Sintering
time
Ф
(nm) Ρ( gcm3 -) a (Å) c(Å) c/a
Ratio
1h 32.3 5.61 3.9229 3.9271 1.051
8h 32.7 6.22 3.9243 3.9392 1.054
24h 34.2 6.00 3.9218 3.9257 1.051
morphological properties
SEM micrographs of the fracture surfaces of compacts sintered at 11000C time 1h,8h and 24h are shown in Figs 2 a,b and c, respectively. Fig. 2a shows that the sample has developed a relatively uniform microstructure with a grain size of 0.7–2.8 μm. Some residual porosity is visible and the fracture appears to have been intergranular. Sintering at 1h leads to a superficially similar microstructure except that some abnormal grain growth occurs. For example, a large grain is visible in Fig. 2c (around 3.5–5μm in diameter) surrounded by smaller particles.
.
Fig. 2. SEM micrographs of fracture surfaces of PbTiO3 samples sintered (a) at 1h ,(b)8h and (c) at 24h.
3 Reflection coefficient (S11) of the resonator
The resonance frequencies of the resonator a b and c range from 9 MHz to 19 MHz. The bandwidth calculated at -10 dB is equal to 0.95 MHz.fig 3.
0,00E+000 2,00E+007 4,00E+007 6,00E+007 8,00E+007 1,00E+008 -30
-25 -20 -15 -10 -5 0
Reflection coefficient (S11) (dB)
Frequency (Hz)
a b c
Fig 3 reflection coefficient (S11) of the a,b and c resonators.
IV. CONCUSION
- Pellets PT manufacture have great tetragonality factor (c
T/ a
T= 1.054) compared to published values around 1.060.
- The resonators manufacture Au / Pt / Au having resonant frequencies between 9 and 19 MHz. It is therefore possible to use them in applications in the fields of mobile telephony and ultrasound waves such as ultrasound.
.
REFERENCES
[1] Bhatti, H. S., Hussain, S. T., Khan, F. A. & Hussain, S.
Synthesis and induced multiferroicity of perovskite PbTiO3; A review. Appl. Surf. Sci. 367, 291–306 (2016).
[2] Iljinas, A., Marcinauskas, L. & Stankus, V. In situ deposition of PbTiO3 thin films by direct current reactive magnetron sputtering. Appl. Surf. Sci.381, 6–
11 (2016).
[3] Forrester, J. S., Zobec, J. S., Phelan, D. & Kisi, E. H.
Synthesis of PbTiO 3 ceramics using mechanical alloying and solid state sintering. 177, 3553–3559 (2004).
[4] Zhang, S., Li, F., Jiang, X., Kim, J. & Luo, J.
Advantages and challenges of relaxor-PbTiO3 ferroelectric crystals for electroacoustic transducers.
Prog. Mater. Sci.68,1–66 (2015).
