71 Original scientific paper  MIDEM Society Journal of Microelectronics, Electronic Components and Materials Vol. 47, No. 2(2017), 71 – 78 Pb(Mg,Nb)O 3 –PbTiO 3 thick films on metalized low-temperature co-fired ceramic substrates H. Uršič1, A. Benčan1,2, E. Khomyakova1, S. Drnovšek1, I. F. Mercioniu3, K. Makarovič1,2,4, D. Belavič5, C. Schreiner6, R. Ciobanu6, P. Fanjul Bolado7, B. Malič1 1Jožef Stefan Institute, Ljubljana, Slovenia 2Centre of Excellence NAMASTE, Ljubljana, Slovenia 3Institutul National Cercetare-Dezvoltare pentru Fizica Materialelor, Bucharest, Romaina 4Keko Equipment Ltd., Žužemberk, Slovenia 5HIPOT-RR d.o.o., Otočec, Slovenia 6Technical University of Iasi, Iasi, Romania 7DROPSENS, Parque Tecnológico de Asturias - Llanera, Spain Abstract: Compatibility of screen-printed piezoelectric 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 thick films with metalized low-temperature co-fired (LTCC) ceramic substrates is examined. Such substrates are interesting for micro-electro mechanical systems, for example for piezoelectric sensors and actuators, where functional layers are usually Pb-based piezoelectrics. In this study the special attention is given to the influence of the Au, Ag and Ag/Pd electrode materials coated over the LTCC on the functional properties of the films. The best phase purity, dielectric and piezoelectric properties were obtained in the films on gilded substrates. No secondary phases were observed at the film/Au interface by scanning electron microscope. The piezoelectric coefficient d33 of the films on gilded substrates is equal to 120 pC/N. Keywords: PMN-PT; piezoelectric; thick film; domain structure; low-temperature co-fired ceramic; LTCC Debele plasti Pb(Mg,Nb)O 3 –PbTiO 3 na podlagah iz keramike z nizko temperature žganja Izvleček: V članku poročamo o pripravi piezoelektričnih 0,65Pb(Mg1/3Nb2/3)O3–0,35PbTiO3 debelih plasti na podlagah iz keramike z nizko temperature žganja. Omenjene podlage so uporabne v mikro elektro mehanskih sistemih, kot so piezoelektrični senzorji in aktuatorji, zato je njihova kompatibilnost s funkcijskimi plastmi velikega pomena. Preučevali smo vpliv spodnje elektrode na lastnosti funkcijskih plasti. Pripravili smo vzorce s tremi različnimi elektrodami, z Ag, Ag/Pd in Au. Ugotovili smo, da plasti na različnih elektrodah izkazujejo različno fazno sestavo, dielektrične in piezoelektrične lastnosti. Plasti na Au elektrodah izkazujejo veliko boljše dielektrične in piezoelektrične lastnosti ter vsebujejo manj sekundarnih faz kot plasti na Ag in Ag/Pd elektrodah. Piezoelektrični koeficient d33 plasti na podlagah iz keramike z nizko temperaturo žganja z zlatimi elektrodami je 120 pC/N. Ključne besede: PMN-PT; piezoelektrik; debela plast; domenska struktura; keramika z nizko temperaturo žganja, LTCC * Corresponding Author’s e-mail: hana.ursic@ijs.si 1 Introduction The thick-film technology is attractive for the produc- tion of simple functional structures and also quite com- plex systems. Screen-printing is one of the most widely used thick-film deposition techniques for producing up to a hundred micrometres thick piezoelectric films. Commercially available piezoelectric thick films are mostly based on Pb(Zr,Ti)O3 solid solution [1]. The most commonly used substrate materials for piezoelectric ceramic thick films are silicon and alumina. However, low-temperature co-fired ceramics (LTCC) are promis- ing for the fabrication of three-dimensional ceramic 72 H. Uršič et al; Informacije Midem, Vol. 47, No. 2(2017), 71 – 78 structures or ceramic micro-electro-mechanical sys- tems (c-MEMS) and for this reason considered as desir- able substrates for functional layers. The LTCC are based on glass-ceramic composites or crystallizing glass and densify at relatively low temperature (around 850 °C), which enables the use of low cost conductive materi- als and fast firing profiles [2, 3]. Therefore the LTCC and thick-film technologies enable fast and easy fabrication of electronic devices and systems, which could reduce the cost of devices and shorten the time of fabrication [2, 4]. The LTCC materials are especially interesting for actuator and sensor applications due to lower Young’s modulus (90–110 GPa) than alumina (210–410 GPa), which enables high actuation sensitivity [1]. An alternative to Pb(Zr,Ti)O3-based piezoelectric ma- terial is (1-x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–100xPT) solid solution with the morphotropic phase boundary at x = 0.35 [5, 6]. The PMN–35PT thick films prepared on silicon and alumina substrates possesses high dielec- tric permittivity (more than 3000 at 1 kHz and room temperature [7-9]) and high piezoelectric coefficients (d33 of 150 to 200 pC/N [9, 10]), and are therefore prom- ising for sensor and actuator applications [11]. The aim of this work was to examine the compatibility of PMN–35PT piezoelectric thick films with metalized LTCC substrates. Until recently, only the Pb(Zr,Ti)O3- based piezoelectric thick films were processed on LTCC substrates [12-15]. But, the glass phase from LTCC may interact with PbZr0.53Ti0.47O3 (PZT) thick film and PbO from the thick film may diffuse into the LTCC during annealing [12, 13], which leads to changes in the thick film’s phase composition and consequently functional properties. Hence the processing of piezoceramic films on LTCC materials is still challenging. In order to pre- vent the film-substrate interactions different solutions were reported, such as interposing of the barrier layer [12] or use of a very dense Au bottom electrode [15]. In this work the PMN–35PT thick films were prepared on metalized LTCC substrates with the interposed 15 mm thick PZT barrier layer to minimize the film-substrate interactions. 2 Experimental methods For the synthesis of the PMN–35PT powder, PbO (99.9 %, Aldrich), MgO (98 %, Aldrich), TiO2 (99.8 %, Alfa Ae- sar) and Nb2O5 (99.9 %, Aldrich) were used. A mixture of these oxides in the molar ratio corresponding to the PMN–35PT stoichiometry with an excess of 2 mol% PbO was high-energy milled for 72 h at 300 rpm in a Retsch Model PM 400 planetary mill, and additionally in an attritor mill for 4 h at 800 rpm in isopropanol. The powder was then heated at 700 °C for 1 h. The size of the particles after heating was determined by a light- scattering technique using a Microtrac S3500 Series Particle Size Analyzer instrument. The results were de- rived from the area particle size distribution. The most common parameter used is the median particle size d50, where the area of all particles smaller than d50 ac- counts for 50 % of the area of all the particles. The pow- der morphology was analysed using the field-emission scanning electron microscopy (FE-SEM) JSM 7600F (Jeol, Tokyo, Japan). The powders were dispersed in ac- etone under ultrasound, and a few drops were spread on highly oriented pyrolytic graphite substrates. The PMN–35PT thick-film paste was prepared from a mix- ture of the PMN–35PT powder and an organic vehicle consisting of alpha-terpineol, [2-(2-butoxy-ethoxy)- ethyl]-acetate and ethyl cellulose in the ratio 60/25/15. For more details on PMN–35PT powder and thick-film paste processing and characterization see [7, 16]. The LTCC substrates were prepared by laminating three layers of the LTCC tape (DuPont 951) at 50 °C and 20 MPa. The laminated tapes were than heated at 450 °C for 1 h to burn-out the organic binder and densified at 875 °C for 15 min. In order to minimize the chemi- cal interactions between the PMN–35PT thick film and the LTCC substrate, a PZT barrier layer was interposed between substrate and bottom electrode as suggest- ed in [7, 17]. The PZT thick-film paste was printed on substrate and sintered 870 °C for 1 h. For more details regarding PZT powder and thick-film paste processing see [7]. The PZT/LTCC structure is further-on referred as the substrate. Thick-film silver (Ag ESL 9912MM), silver/ palladium (80Ag/20Pd FERRO EL44-001) and gold (Au ESL 8884G) conductors were printed on the barrier lay- er/substrate structures and fired at 850 °C for 1 h. The thicknesses of the sintered electrodes were 50, 25 and 25 mm, respectively. The PMN–35PT paste was printed five times on the electrode substrate with intermediate drying at 150 °C after each printing step. The samples were pressed at 50 MPa, heated at 500 °C for 1 h to decompose the or- ganic vehicle [16], sintered at 850 °C for 2 h in covered alumina crucibles in the presence of PbZrO3 packing powder with an excess of 2 mol% PbO and then cooled to room temperature with a rate of 2 °C/min. The X-ray diffraction (XRD) patterns of the films were recorded using a PANalytical X’Pert PRO MPD (X’Pert PRO MPD, PANalytical, Almeo, The Netherlands) diffrac- tometer with Cu–Kα1 radiation. The XRD patterns were recorded in the 2q region from 10° to 70° using a detec- tor with a capture angle of 2.122°. The exposure time for each step was 100 s and the interval between the obtained data points was 0.034°. 73 For microstructural analysis the samples were mounted in epoxy, ground and polished using standard metal- lographic techniques. The microstructures of the sam- ples were investigated with a FE-SEM JSM 7600F (Jeol, Tokyo, Japan) equipped with an Inca Energy Detector. The energy-dispersive X-ray spectroscopy (EDXS) anal- yses were performed at 15 keV. The average grain size (GS) was estimated from the SEM images obtained by backscattered electrons (BE) of the film’s surface. For the stereological analysis more than 400 grains per sample were measured with the Image Tool Software. The GS is expressed as the Feret’s diameter. The topography and piezoresponse images were re- corded with an atomic force microscope (AFM; Asylum Research, Molecular Force Probe 3D, Santa Barbara, CA, USA) equipped with a piezoresponse force mode (PFM). A tetrahedral Si tip coated with Ti/Ir (Asyelec-01, Atomic- Force F&E GmbH, Mannheim, Germany) with the curva- ture diameter of 30 nm ± 10 nm was applied for scanning the sample surface. The out-of-plane amplitude PFM im- ages were measured in the Single mode at ac amplitude signal of 20 V and frequency of ~300 kHz. The local am- plitude and phase hysteresis responses were measured in the Dual AC Resonance Tracking Switching Spectros- copy (DART-SS) mode with the waveform parameters: increasing step signal with maximum amplitude of 60 V and frequency 0.1 Hz; overlapping sinusoidal signal of amplitude 5 V and frequency 20 Hz, off-loop mode. For dielectric and piezoelectric measurements, Cr/Au electrodes with a 1.5-mm diameter were deposited on the top surface of the films using RF-magnetron sputtering (5 Pascal). The dielectric permittivity (ε`) and dielectric losses (tan δ) versus temperature were measured with a HP 4284 A Precision LCR Meter by ac amplitude of 1 V and frequencies of 1, 10, and 100 kHz during cooling from 300 °C to 25 °C. The films were poled at 160 °C with a dc electric field from 2.5 to 7.5 kV/mm for 5 min and field-cooled to 25 °C. After pol- ing the samples were aged for 24 h. The piezoelectric constants d33 were measured by Berlincourt piezome- ter (Take Control PM10, Birmingham, UK) at alternating stress frequency of 100 Hz. 3 Results and discussion 3.1 Characterisation of PMN–35PT powder The particle size distribution of the PMN–35PT powder used for preparation of the thick-film paste is shown in Figure 1(a). The d50 was 0.32 mm. Around 10 % of the particles are larger than 1 mm, while the majority of them has a sub-micrometre size. Such distribution was confirmed by the FE-SEM analysis, where both fine sub- micrometre and coarse particles were observed (Figure 1(b)). The XRD pattern of PMN–35PT mechanochemi- cally synthesized powder after calcination at 700 °C is shown in Figure 1(c). All reflections correspond to the perovskite phase. Figure 1: (a) The area particle size distribution, (b) FE- SEM micrograph and (c) XRD pattern of the PMN–35PT powder after heating at 700 °C for 1 h. A coarse par- ticle and smaller, submicron sized particles are marked by an arrow and a circle in panel (b), respectively. The indexed peaks of the pseudo-cubic perovskite phase (JCPDS 81-0861) are shown in brackets in panel (c). H. Uršič et al; Informacije Midem, Vol. 47, No. 2(2017), 71 – 78 74 3.2 The influence of the bottom electrode material on the phase composition and functional properties of PMN–35PT films In order to study the influence of the bottom electrode layer on the properties of functional thick-film struc- tures three different electrode materials were used; Ag, Ag/Pd and Au. Corresponding XRD patterns of ~60 mm thick PMN–35PT films on the metalized substrates are shown in Figure 2. Figure 2: (a) XRD patterns of PMN–35PT thick films on Ag-, Ag/Pd- and Au-metalized substrates. The indexed peaks of the pseudo-cubic perovskite phase are shown in brackets (JCPDS 81-0861). (b) An enlarged 2θ-region from 23 to 65°. The peaks corresponding to PbO (JCPDS 78-1664) and pyrochlore Pb1.83Nb1.71Mg0.29O6.39 (JCPDS 33-0769) are marked by o and x, respectively. The re- flection, which cannot be clearly identified by crystallo- graphic cards, is marked by a question mark in Fig. (b). In addition to the perovskite reflections, also low-in- tensity PbO and pyrochlore reflections are observed in XRD patterns of the films on Ag- and Ag/Pd-metal- ized substrates. In the latter, also one reflection exists, which cannot be clearly identified by crystallographic cards in JCPDS base (marked by a question mark in Fig- ure 2(b)). Note that the penetration depth of X-rays in PMN−35PT thick films is around 10 μm [10] and there- fore the results show only the composition of the up- per part of the thick films. On the other hand in the XRD pattern of PMN–35PT thick film on Au-metalized substrate the perovskite reflections and only a trace of two reflections corresponding to PbO phase can be observed. These low-intensity diffraction peaks are most probably related to the initial excess of PbO in the starting powder mixture (see Experimental methods). The secondary phases determined from the XRD pat- terns together with the dielectric properties of PMN– 35PT thick films on metalized substrates are collected in Table 1. Table 1: The secondary phases (SP) determined from the XRD patterns, the room-temperature dielectric and piezoelectric properties of PMN–35PT thick films on metalized substrates. electrode SP ε` at 10 kHz tan δ at 10 kHz d33 at 5.5 kV/mm Ag PbO, Py 250 /* / Ag/Pd PbO, Py, UP 300 0.04 / Au traces of PbO 1050 0.04 120 /not possible to pole /*not possible to measure at 10 kHz, tan δ is 0.06 at 100 kHz UP-unidentified phase, Py-pyrochlore The dielectric permittivity of the films on Au-metal- ized substrates is 1050 at 10 kHz, which is more than three times higher than in the films on Ag- and Ag/ Pd-metalized substrates. The tan δ of films on Au- and Ag/Pd-metalized substrates are in the same range. For films on Ag-metalized substrates the tan δ at 10 kHz was not possible to measure. Low values of ε` (i.e. 235) were previously reported also for PZT films on Ag/ Pd-metalized LTCC (with no barrier layer between the LTCC and the electrode layer), which was attributed to intense interactions between the functional film and the substrate [14]. Furthermore, we were able to pole only the films on Au-metalized substrates (Table 1). The measured d33 coefficient of such films is 120 pC/N. Due to the superior phase purity, dielectric properties and ability of poling, we further analysed only the PMN– 35PT films on Au-metalized (gilded) substrate. The mi- crostructural, dielectric properties as a function of tem- perature and piezoelectric properties of these films are further discussed below. 3.3 The PMN–35PT thick films on gilded substrates The photo of a PMN–35PT thick film on the gilded sub- strate is shown in Figure 3(a). The thick film surface is crack-free on cm scale. The BE-SEM images of the sur- face and polished cross-section of the film are shown H. Uršič et al; Informacije Midem, Vol. 47, No. 2(2017), 71 – 78 75 in Figure 3(b) and (c), respectively. Fig. 3(b) reveals a porous, but uniform microstructure. The estimated av- erage grain size is ~0.8 μm. Some PbO, seen as a white inclusion in Figure 3(b), is also present in the film. The results are in accordance with the XRD analysis, where in addition to the perovskite phase, a trace amount of PbO phase was also detected (see Fig. 2(b)). As seen in Figure 3(c) the thicknesses of the PZT barrier layer, Au and PMN–35PT film are ~15, ~25 and ~60 mm, respec- tively. The thickness of the PMN–35PT film is quite ho- mogeneous across the substrate. No secondary phases are observed at the PMN–35PT/Au interface (inset in Figure 3(c)). Below the PZT layer into the LTCC sub- strate, a ~50 mm thick, brighter layer is formed (marked with an arrow). According to the EDXS analysis, this layer is PbO-rich and can be attributed to diffusion of PbO from PZT into the LTCC. Such layer was previ- ously reported also in PZT/Au/LTCC structures, where the PbO diffused from the PZT functional layer into the substrate [13]. In Figure 4 the ε` and tan δ as a function of tempera- ture are shown for the PMN–35PT thick film on gilded substrate. At 30 °C and 1 kHz the ε` and tan δ are 1150 and 0.06, respectively. The temperature of ε`max (∼4800) at 1 kHz is 166 °C ± 1 °C, which is in agreement with the previously published temperature for PMN–35PT bulk ceramics [18, 19]. The ε` at room temperature is approxi- mately three times lower than the one of the films on platinized alumina [7, 8] and approximately four times lower than PMN–35PT bulk ceramics [20], which could be attributed to the higher porosity and smaller average grain size of studied films on gilded LTCC substrates. On the other hand, the prepared films exhibit at least two times higher ε` at room temperature than previously published PZT films on LTCC substrates [12-14]. Figure 4: (a) ε’ and (b) tan δ of the PMN–35PT film on gilded substrate as a function of temperature at 1, 10 and 100 kHz. Figure 3: (a) The photo and BE-SEM images of (b) thick film surface and (c) polished cross-section of PMN– 35PT thick film on gilded substrate. The thick arrow in panel (b) marks the PbO phase. In panel (c) the exten- sion of a Pb rich layer in the LTCC is marked by an ar- row and the inset shows an enlarged view of the PMN– 35PT/Au interface. H. Uršič et al; Informacije Midem, Vol. 47, No. 2(2017), 71 – 78 76 Further the local piezoelectric response and ferro- electric domain configuration were investigated. The topography and out-of-plane PFM amplitude images are shown in Figure 5 (a) and (b), respectively. In the topographical image, the grain boundaries can be clearly identified, while in the amplitude image the grain boundaries are visible as dark non-active bound- aries. The enhanced local piezoelectric activity is evi- dent as brighter areas within the grains. An example of such region is marked by no. 1 in Figure 5 (b). The most frequently observed domains in the film are ir- regularly shaped domains found also in Pb(Sc0.5Nb0.5)O3 [21]. The size of the domains varies from a few hundred nanometres to a micrometre. Examples of such irreg- ularly shaped domains are marked by thick arrows in Figure 5 (b). In addition rear lamellar-like domains can be found (marked by a thin arrow). Irregularly shaped and lamellar domains were previously observed also in PMN–35PT films on alumina substrates [22]. The local PFM amplitude and phase hysteresis loops are shown in Figure 5 (c) confirming a typical hysteretic response of the ferroelectric material and indicating the local do- main switching. The PMN–35PT thick films were poled with a dc elec- tric field of 2.5–7.5 kV/mm as described in Experimen- tal section. The d33 values are collected in Table 2. For the films poled at 2.5 kV/mm, the d33 was 65 pC/N, but it increased with the increasing poling field until 5.5 kV/mm. The highest d33 of 120 pC/N was measured for the samples poled at electric field amplitudes be- tween 5.5 and 7.5 kV/mm. The d33 coefficient is only 20 % lower than the one reported for PMN–35PT films on platinized alumina, i.e., ~150 pC/N for similar film thick- ness [10]. We note that the reduction of d33 in PZT thick films deposited on LTCC or on alumina was much more pronounced than in our PMN-PT films; i.e., 75 pC/N ver- sus 125 pC/N, which is about 40 %. Such strong dete- rioration of the piezoelectric response was attributed to the interaction between the PZT film and the LTCC substrate [13]. It is also important to mentioned that the piezoelectric coefficient of PMN–35PT bulk ceram- ics prepared from the mechanochemically synthesized powder, but sintered at 1200 °C is ~640 pC/N (at similar poling conditions; electric field of 4.5 kV/mm) [20]. Table 2: The piezoelectric coefficient d33 measured for the PMN–35PT films poled at different electric field am- plitudes. Epoling (kV/mm) d33 (pC/N) 2.5 65 3.5 85 4.5 100 5.5 120 6.5 120 7.5 120 Figure 5: (a) Topography and (b) out-of-plane PFM amplitude image of the PMN–35PT thick film on gild- ed substrate. (c) PFM amplitude and phase hysteresis loops obtained from the areas marked by no. 1, 2 in the panel (b). H. Uršič et al; Informacije Midem, Vol. 47, No. 2(2017), 71 – 78 77 The degradation of dielectric and piezoelectric prop- erties of the PMN–35PT films on metalized LTCC sub- strates in comparison to the properties of the films on metalized alumina substrates could be related to the higher porosity of the films deposited on the former substrates. Further work is thus needed to improve the densification of the films on LTCC substrates. 4 Summary and conclusions The compatibility of piezoelectric PMN–35PT thick-films with metalized LTCC substrates (DuPont 951) was stud- ied. Three different bottom electrodes were used; Ag, Ag/Pd and Au. The XRD analysis revealed the presence of a large amount of secondary phases in the films pre- pared on Ag- and Ag/Pd-metalized substrates, while in the film deposited on the Au-metalized substrate only a trace of PbO phase was detected. Furthermore, about three times higher room temperature dielectric permit- tivity (1050 at 10 kHz) was measured in the films on Au- in comparison to the ones on Ag- and Ag/Pd-metalized substrates. The films on Ag- and Ag/Pd-metalized sub- strates could not be poled, but the ones on gilded sub- strates exhibit the piezoelectric coefficient d33 as high as 120 pC/N. Irregularly-shaped and lamellar-like domains with the size from a few hundred nanometres to micro- metres were observed and the domain switching was confirmed by piezo-response force microscopy. In conclusion, we succeeded to prepare ~60 mm thick PMN–35PT films on gilded substrates, where no film- substrate interactions were observed by SEM. The films exhibit high piezoelectric properties, much higher than the ones previously published for lead-based thick films on LTCCs. However, further work is needed to improve the densification of these films aiming to further enhance their functional properties. 5 Acknowledgements This work was funded by M-ERA.NET project “Integrated sensors with microfluidic features using LTCC Technology” INTCERSEN (PR-06211) and the Slovenian Research Agency (research core funding No. P2-0105). Techni- cal support by Mitja Jerlah, Jena Cilenšek, Brigita Kmet, Aneja Tuljak and Mateo Markov (Erasmus+ program) is gratefully acknowledged. 6 References 1. Zarnik M S, Ursic H, Kosec M. Recent progress in thick-film piezoelectric actuators prepared by screen-printing, in: Piezoelectric Actuators (open access), J. E. Segel, Ed., Nova Science Publishers Inc., 2011. https://www.novapublishers.com/cat- alog/product_info.php?products_id=30015 2. Imanaka Y. Multilayered low temperature co- fired ceramics (LTCC) technology. New York, USA, Springer, 2005. http://link.springer.com/ book/10.1007%2Fb101196 3. Makarovic K, Meden A, Hrovat M, Holc J, Bencan A, Dakskobler A, Kosec M. The effect of process- ing conditions on the properties of LTCC mate- rial, J. Am. Ceram. Soc., 2012; 95: 760–767. http:// onlinelibrary.wiley.com/doi/10.1111/j.1551- 2916.2011.05027.x/abstract 4. Belavic D, Hrovat M, Zarnik MS, Holc J, Kosec M. An investigation of thick PZT films for sensor ap- plications: A case study with different electrode materials, J. Electroceram., 2009; 23: 1–5. http:// link.springer.com/article/10.1007/s10832-008- 9495-1 5. Singh A K, Pandey D. Evidence for MB and MC phases in the morphotropic phase boundary region of (1-x)[Pb(Mg1/3Nb2/3)O3]–xPbTiO3: A riet- veld study, Phys. Rev. B, 2003; 67, 064102 1–12. https://journals.aps.org/prb/pdf/10.1103/Phys- RevB.67.064102 6. Handbook of Advanced Dielectric, Piezoelectric and Ferroelectric Materials, Z.-G. Ye, Ed. Cam- bridge, England, Woodhead Publishing Ltd, 1st ed., 2008. http://www.sciencedirect.com/sci- ence/book/9781845691868 7. Ursic H, Hrovat M, Holc J, Tellier J, Drnovsek S, Guib- lin N, Dkhil B, Kosec M. Influence of the substrate on the phase composition and electrical proper- ties of 0.65PMN–0.35PT thick films, J. Eur. Ceram. Soc., 2010; 30: 2081–2092. http://www.sciencedi- rect.com/science/article/pii/S0955221910001615 8. Gentil S, Damjanovic D, Setter N. Development of relaxor ferroelectric materials for screen-printing on alumina and silicon substrates. J. Eur. Ceram. Soc., 2005; 25: 2125–2128. http://www.sciencedi- rect.com/science/article/pii/S095522190500169X 9. Gentil S, Damjanovic D, Setter N. Pb(Mg1/3Nb2/3)O3 and (1-x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 relaxor fer- roelectric thick films: processing and electrical characterization. J. Electroceram., 2004; 12: 151– 161. http://link.springer.com/article/10.1023/B:- JECR.0000037720.39443.e3 10. Ursic H, Zarnik, MS, Tellier J, Hrovat M, Holc J, Kosec M. The influence of thermal stresses on the phase com- position of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 thick films, J. Appl. Phys., 2011; 109: 014101 1–5. http:// aip.scitation.org/doi/full/10.1063/1.3526971 11. Ursic H, Zarnik MS, Kosec M. Pb(Mg1/3Nb2/3)O3– PbTiO3 (PMN–PT) material for actuator applica- tions, Smart Materials Research (open access), H. Uršič et al; Informacije Midem, Vol. 47, No. 2(2017), 71 – 78 78 2011; 2011: 452901 1–6. https://www.hindawi. com/journals/smr/2011/452901/ 12. Hrovat M, Holc J, Drnovsek S, Belavic D, Cilensek J, Kosec M. PZT thick films on LTCC substrates with an interposed alumina barrier layer, J. Eur. Ceram. Soc., 2006; 26: 897–900. http://www.sciencedi- rect.com/science/article/pii/S0955221905000634 13. Ursic H, Hrovat M, Belavic D, Cilensek J, Drnovsek S, Holc J, Zarnik MS, Kosec M. Microstructural and electrical characterisation of PZT thick films on LTCC substrates, J. Eur. Ceram. Soc., 2008; 28: 1839–1844. http://www.sciencedirect.com/sci- ence/article/pii/S0955221908000253 14. Golonka L J, Buczek M, Hrovat M, Belavic D, Dziedzic A, Roguszczak H, Zawada T, Properties of PZT thick films made on LTCC, Microelectronics Int., 2005; 22: 13–16. http://www.emeraldinsight. com/doi/abs/10.1108/13565360510592171 15. Gebhardt S, Seffner L, Schlenkrich F, Schonecker A. PZT thick films for sensor and actuator appli- cations, J. Eur. Ceram. Soc., 2007; 27: 4177–4180. http://www.sciencedirect.com/science/article/ pii/S095522190700163X 16. Ursic H, Tchernychova E, Bencan A, Jouin J, Holc J, Drnovsek S, Hrovat M, Malic B. The influence of the platinum substrate roughness on the fer- roelectric properties of 0.65Pb(Mg1/3Nb2/3)O3– 0.35PbTiO3 thick films, Informacije MIDEM, Jour- nal of Microelectronics, Electronic Components and Materials (open access), 2014; 44: 12–18, http:// www.midem-drustvo.si/Journal%20papers/ MIDEM_44(2014)1p12.pdf 17. Holc J, Hrovat M, Kosec M. Interactions between alumina and PLZT thick films. Mater. Res. Bull., 1999; 34: 2271–8. http://www.sciencedirect.com/ science/article/pii/S0025540899002275 18. Alguero M, Ricote J, Jimenez R., Ramos P, Carreaud J, Dkhil B, Kiat J M, Holc J, Kosec M. Size effect in morphotropic phase boundary Pb (Mg1/3Nb2/3)O3–PbTiO3, Appl. Phys. Lett., 2007; 91: 112905 1–3. http://aip.scitation.org/doi/ abs/10.1063/1.2778471 19. Leite E R, Scotch A M, Khan A, Li T, Chan H M, Harmer M P, Liu S F and Park S E. Chemical he- terogeneity in PMN–35PT ceramics and effects on dielectric and piezoelectric properties, J. Am. Ceram. Soc., 2002; 85: 3018–3024. http://online- library.wiley.com/doi/10.1111/j.1151-2916.2002. tb00572.x/abstract 20. Ursic H, Tellier J, Hrovat M, Holc J, Drnovsek S, Bobnar V, Alguero M, Kosec M. The Effect of Po- ling on the Properties of 0.65Pb(Mg1/3Nb2/3)O3– –0.35PbTiO3 Ceramics, Jpn. J. Appl. Phys., 2011; 50: 035801-6. 21. Ursic H, Drnovsek S, Malic B. Complex doma- in structure in polycrystalline Pb(Sc0.5Nb0.5)O3, J. Phys .D: Appl. Phys., 2016; 49: 115304 1–4. http://iopscience.iop.org/article/10.1088/0022 -3727/49/11/115304 22. Ursic H, Ricote J, Amorin H, Holc J, Algue- ro M. Ferroelectric domain configurations in 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 thick films determined by piezoresponse force mi- croscopy, J. Phys. D: Appl. Phys., 2012; 45: 265402 1–11. http://iopscience.iop.org/arti- cle/10.1088/0022-3727/45/26/265402 Arrived: 17. 04. 2017 Accepted: 13. 07. 2017 H. Uršič et al; Informacije Midem, Vol. 47, No. 2(2017), 71 – 78