The possibilities of the application of the microstructure analysis, X-ray powder diffraction, and Raman scattering methods for the fast and reliable control of the quality of piezoelectric ceramic sensors at every stage of preparation are shown

Dudek, Julian

Kozielski, Lucjan

Kuprijanov, M. F.

Surowiak, Zygmunt

Archives of Acoustics

English

Repozytorium Uniwersytetu Śląskiego RE-BUŚ

             Title: The influence of preparation conditions on the electro-acoustic properties of the PZT-type piezoceramic sensors  Author: Julian Dudek, Lucjan Kozielski, Zygmunt Surowiak, M. F. Kuprijanov  Citation style: Dudek Julian, Kozielski Lucjan, Surowiak Zygmunt, Kuprijanov M. F. (2000). The influence of preparation conditions on the electro-acoustic properties of the PZT-type piezoceramic sensors. "Archives of Acoustics" (Vol. 25, nr 1 (2000) s. 35-42).  ARCHIVES OF ACOUSTICS25, 1, 35–42 (2000)THE INFLUENCE OF PREPARATION CONDITIONSON THE ELECTRO-ACOUSTIC PROPERTIES OFTHE PZT-TYPE PIEZOCERAMIC SENSORSJ. DUDEK, L. KOZIELSKI, Z. SUROWIAKSilesian University of Technology,Department of Materials Science(41-200 Sosnowiec, 2 Śnieżna Str., Poland)e-mail:surowiak@us.edu.plM.F. KUPRIYANOVRostov on Don State University, Faculty of Physics(344-104 Rostov on Don, 5 Zorge Str., Russia)The possibilities of the application of the microstructure analysis, X-ray powder diffrac-tion, and Raman scattering methods for the fast and reliable control of the quality ofpiezoelectric ceramic sensors at every stage of preparation are shown.1. IntroductionFor the past several years an intensive research effort have been made in many labora-tories around the world to prepare electrically active ceramic materials intended for elec-tromechanical transducers and other applications. Ferroelectric ceramic materials suchas Pb(TixZr1−x)O3 (PZT) solid solutions have been used extensively as both sensorsand actuators due to their excellent transduction capability in elastoelectric conversion[1 – 4]. Such piezoceramics have the strongest piezoelectric charge coefficients, the largestelectromechanical coupling coefficients and relative permittivities as well as the lowestdielectric losses. The large permittivities of PZT ceramic materials facilitate electricaltuning and also reduce significantly the piezoelectric voltage coefficients. The PZT ce-ramic materials have large mechanical quality factors (Qm) and require the addition ofa damping backing in order to reduce ringing to an acceptable level.The composition of PZT-type with conductive parameters of widespread applicationbelongs, as a rule, to the morphotropic phase boundary (MPB) — a region of concen-trations x for which a coexistence of both the rhombohedral (R) and tetragonal (T)ferroelectric phases is observed [5 – 7]. The interval of the composition parameter x atwhich both these phases appear is relatively wide, it may reach 15 mol%. One of the char-acteristic properties of MPB is a small deviation from the temperature axis on the phase36 J. DUDEK et al.diagram which corresponds to the large change of structural states with temperature forfixed concentration x. These peculiarities of MPB and of its vicinity are characterizedby the most interesting properties of the corresponding materials: extreme values of thepiezoelectric and dielectric parameters (Fig. 1). However, there are many problems inthe processing of high quality ceramic materials on the basis of compounds from MPB.Fig. 1. The dependencies of physical parameters of the PZT-type system in the vicinity of the mor-photropic phase boundary on the PbTiO3 content.THE INFLUENCE OF PREPARATION CONDITIONS 37It was shown (e.g [8 – 10]) that the properties of such ferroelectric ceramic materialsdepend strongly on the conditions of their preparation, i.e. on the synthesis, sintering,mechanical treatments, annealing and polarization processes. This is connected with thehigh sensitivity of these materials to the changes of the structural states of the MPBwith small variations in composition, grain size, domain structure etc.It is evident that at all stages of the production of the ceramics (synthesis, sintering,mechanical treatments, annealing and polarization) it is necessary to apply effective (fast,reliable, precise, nondestructive) control methods.The aim of this paper is to analyse the possibilities of characterization of the PZT-type ferroelectric materials at every stage of the ceramic sample preparation by effectivecontrol methods. The best methods for this purpose are, in our opinion, X-ray diffraction(XRD), microstructure analysis and Raman spectroscopy.2. ExperimentalOn the basis of the PZT-type solid solutions, the materials from MPB were preparedby the solid-phase synthesis methods. Ceramic samples were obtained under differentconditions of preparation (varying times and temperatures) both by the usual sinteringand by the hot-pressing method. The samples were investigated by the X-ray powderdiffraction method at the stage of the preparation of the components for the synthesis,after synthesis, after sintering and after polarization. The investigations of the microstruc-ture of the ceramic samples were performed led by the electron microscope method. TheRaman spectra were excited by argon laser light (λ = 0.488 m).3. ResultsAt the first stage, the dependencies of the piezoelectric and dielectric parameters onthe conditions of the sample preparation of the PZT compositions from the MPB regionwere investigated. The results for one sample are presented in Fig. 2.From the data given in Fig. 2, it results that the small differences in the conditionsof preparation of the ceramic material can lead to significant differences in the physicalproperties. If the methods of control of the ceramic materials had not been applied duringthe preparation, the results of measurements of the physical properties of the fabricatedceramic samples would be rather irrational because spoilt ceramic materials hardly meetthe requirements for a given application.Control of the microstructure is done, as a rule, for the characterization of the ferro-electric ceramics at various stages of its sintering [11 – 13].As an example in Fig. 3 the correlations between some electrophysical parameters,dimensions of the crystallites and total density (for samples obtained by hot-pressingmethod) are shown. It was expected that the influence of the hot pressing on the mi-crostructure would be larger that in the case of conventional sintering.It was found that the influence of the time and temperature of the sintering on thedimensions of grains is noticeable (Fig. 3a).38 J. DUDEK et al.Fig. 2. The dependencies of the dielectric permittivities (εmax), electromechanical coupling coefficients(kp), Curie temperature (Tc) and phase transition diffuseness parameters (∆d) on the sintering temper-ature (Tsint) (sintering time, tsint = 2hours); a) the dependencies of εmax, ε0, kp, Tc on the sinteringtemperature and time (tsint: 1-0.25; 2-2; 3-3; 4-5 hours) (b, c, d).The decrease in the dielectric permittivities (ε/ε0) with increasing grain sizes (Fig. 3b)is due to a decrease in the internal strains of the specimen brought about by an increaseddomain twinning in the larger grains.The electromechanical coupling coefficient (kp) was practically independent of thedimensions of the grains but its value is related to the bulk density (Fig. 3c).It is possible to explain the decrease of coercive field Ec and the monotonic decreaseof the Qm values by the grain size increase (Fig. 3d). This effects could be explained alsoas a result of the increased twinning during the grain size increase. The latter causes anincrease in the number of the domain walls which lead to higher mechanical losses andthereby to a lower Qm.At the same time the analysis of the microstructure may be in general effectively usedonly at the stage of sintering. Its possibilities are limited to the control of other stagesof preparation of the ferroelectric elements (synthesis, polarization etc).The most suitable method of the production process control is the X-ray powderdiffraction methods by that one can determine: i – the crystal phases and their con-centrations in specimens; ii – the crystal phase symmetries and the cell parameters;iii – the values of spontaneous deformations; iv – mechanical and electrical (domain) tex-ture parameters; v – microinhomogeneities (microdeformations); vi – values of coherentscattering regions (CSR).THE INFLUENCE OF PREPARATION CONDITIONS 39Fig. 3. The dependencies of the grain size on the sintering temperature and time (a), the dependenciesof ε/ε0, the electromechanical coupling (kp), coercive fields (Ec), and mechanical quality factors (Qm)on the grain sizes of the ceramics (b, c, d).For the determination of the structural parameters of powder (ceramic) specimensthe mathematical treatment of the diffraction profiles (Fig. 4a) has been used. Differentmethods of such a treatment are described in [14, 15]. Figure 4b demonstrates two exam-ples of separation of the three diffraction peaks related to the R — (200R), T — (200T ,002T ) phases which coexist in MPB of the PZT-type materials.A comparison of the diffraction profiles obtained for ceramics sintered at differentτsint and Tsint indicates that high degree of homogeneity is possible at lower Tsint if thesintering time is increased. Figure 4 shows a decrease of the amount of the R-phase andnarrowing of the diffraction peak of the T-phase.A separation of the overlapped peaks allows both the determination of the cell pa-rameters and the evaluation of the microinhomogeneities η = ∆d/d and the coherentscattering region (CSR) dimensions by the analysis of full width of the half maxima(FWHM) of the diffraction peaks. These parameters are very sensitive to the real stateof the ferroelectric materials.The estimation performed is due to the fact that the microinhomogeneity value in theparaelectric cubic phase does not exceed 10−4 and the CSR dimensions, as a rule, arefound to be larger than 100 nm (for ceramics produced under the optimal conditions).Changes of the CSR values are observed at the MPB transitions to the ferroelectricT- and R-phases.The conditions of sintering of the ceramic materials from MPB have an influence onboth the percentage of the ratio of the R to the T phases and of the FWHM as shown40 J. DUDEK et al.Fig. 4. The X-ray powder diffraction profile (a) and the separation method of overlapped peaks (b):1 – sample hot pressing, 2 – classic sample technology; the change of the diffraction profile as a result ofdifferent sintering times (1 – tsint = 0.25h; 2 – tsint = 5h; Tsint = 1223K) (c).in Fig. 4. With an increase in the sintering temperature up to 1398 K the concentrationof the T phase at room temperature increases and the FWHM of the difraction peaksdecreases.The influence of the electric fields of polarization on the structure and the physicalproperties of the PZT-type ceramics was discussed elsewhere [16 – 18].THE INFLUENCE OF PREPARATION CONDITIONS 41The spectra of the Raman scattering are sensitive to the dynamical state of the crys-tals [19 – 20]. In particular, by means of the IR methods, the Raman- and Brillouin-spectroscopy it is possible to investigate the softening of the transverse optical (ferro-electric) mode above the phase transition.In this paper the preliminary results of the Raman investigations of the PZT-systemsamples are presented. It is worthy of noting that all samples were obtained under thesame conditions of the synthesis and sintering (Fig. 5).Fig. 5. The dependencies of the mode frequencies of the PZT systems on the PbTiO3 concentrationobtained by the Raman spectroscopy (argon laser).It seems reasonable to assume that the A-mode is the ferroelectric E(TO) one. Itbecomes softer while approaching to the MPB (concentration phase transition at roomtemperature). The B mode may be treated as the TA-transverse acoustic one. The C-mode appears in the rhombohedral phase of the solid solutions only and may be relatedto RLT(R3c) phase. It may be caused by the M3- or R25-type phase transitions.In our opinion the further investigations of the specific vibration spectra of the PZT-type ferroelectric materials obtained under various conditions allow to separate the de-pendencies of the corresponding parameters on the quality of the crystallites. As a resultit should give the possibility to apply the combinational light scattering method to theoperative control of the quality of the material at all stages of the production.4. ConclusionThe results of the studies of the PZT-type ceramics with compositions from MPB pre-sented above demonstrate that the variation of preparation conditions strongly determinethe physical properties of the piezoelectric ceramic sensors.An effective control of the ceramics fabrication at the different stages of the productioncan be performed by the X-ray powder diffraction methods.42 J. DUDEK et al.AcknowledgementsThe authors would like to thank the Committee for Scientific Research (KBN),Poland, for financial support under grant No. 7T08D 005 17.Keywords: PZT, piezoceramics, electro-acoustic sensors, Raman spectroscopy, XRD.References[1] B. Jaffe, W.R. Cook, H. Jaffe, Piezoelectric ceramics, Acad. Press, New York 1971.[2] K. Okazaki, Bull. Am. Ceram. Soc, 63, 9, 1150 (1984).[3] C.A. Rogers, J. Intell. Mater. Syst. Struct, 4, 4 (1993).[4] L.E. Cross, J. Intell. Mater. Syst. Struct., 6, 55 (1995).[5] G. Shirane, K. Suzuki and A. Takeda, Phys. Soc. Japan, 7, 12 (1952).[6] V.A. Isupov, Solid St.Commun., 17, 1331 (1975).[7] M. Kupriyanov, G. Konstantinov and A. Panich, Ferroelectric morphotropic transitions, RGU,Rostov-on-Don 1992.[8] J. Dudek and M. Kupriyanov, Inżynieria Materiałowa, 6, 71, 129 (1992).[9] A. Panich and M. Kupriyanov, Physics and technology of ferroelectric ceramics, RGU, Rostov-on-Don 1989.[10] Z. Surowiak, J. Dudek and M. Łoposzko, Inżynieria Materiałowa, 6, 71, 123 (1992).[11] K. Okazaki, Ceramic engineering for dielectrics, Tokyo 1969.[12] Z. Surowiak and V.P. Dudkevich, Cienkie warstwy ferroelektryczne, Uniw. Śl., Katowice 1996.[13] R.C. Buchanan, T.R. Armstrong and R.D. Roseman, Ferroelectrics, 135, 343 (1992).[14] V. Kogan and M. Kupriyanov, J. Appl. Cryst., 25, 16 (1992).[15] J. Dudek J., Ya. Bogosova, D. Czekaj, G. Konstantinov, M. Kupriyanov and A. Panich,Proc. of 15th Conf. Appl. Cryst., Cieszyn, Poland, p. 278 (1992).[16] J. Kwapulinski, Z. Surowiak, M. Kupriyanov et al., ZTF, 49, 1049 (1979).[17] J. Dudek, M.F. Kupriyanov, M. Loposzko and E.G. Fesenko, Acta Physica Polonica, A63, 115(1983).[18] G. Konstantinov, M. Kupriyanov, V. Servuli et al., ZTF, 59, 80 (1989).[19] M.E. Lines and A.M. Glass, Principles and application of ferroelectrics and related materials,Clarendon Press, Oxford 1977.[20] T. Błachowicz and Z. Kleszczewski, Akustyka Mol. i Kwantowa, 16, 23 (1995).

The influence of preparation conditions on the electro-acoustic properties of the PZT-type piezoceramic sensors

https://rebus.us.edu.pl/bitstream/20.500.12128/13129/1/Dudek_The%20influence_of_preparation.pdf

The influence of preparation conditions on the electro-acoustic properties of the PZT-type piezoceramic sensors

Abstract

Similar works

Full text

Available Versions

Repozytorium Uniwersytetu Śląskiego RE-BUŚ