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|Processing of 0.65 Pb(Mg(1/3)Nb(2/3))O(3) - 0.35 PbTiO(3) Thick-Films on LTCC Ceramic Substrates|
|Keywords: PMN-PT, LTCC, screen printing|
|Pb(Mg1/3Nb2/3)O3 - PbTiO3 (PMN-PT) based materials exhibit high dielectric constant, high electrostrictive and piezoelectric properties and are suitable for applications in multilayer capacitors, actuators, sensors and electro-optic devices. To downsize the final device, the active material needs to be miniaturised and integrated with the substrate. 0.65 Pb(Mg1/3Nb2/3)O3 - 0.35 PbTiO3 nano-sized powder was prepared from the constituent oxide mixture with a 2 mol. % PbO excess by mechanochemical synthesis. The paste for screen-printing was prepared from the obtained powder and an organic vehicle, and printed on two types of ceramic substrates, i.e. platinised alumina and gold-coated low temperature co-fired ceramics (LTCC). Thick film structures on LTCC were sintered at 850 oC, while that ones on alumina substrates were sintered up to 950 oC. Dense, homogeneous, single phase PMN-PT thick films on alumina without any pyrochlore phase were obtained after the sintering. The obtained thick-film structures exhibit dielectric and ferroelectric properties comparable to bulk PMN-PT ceramics. Screen printed PMN-PT on gold-coated LTCC substrates intensively reacts with the components from LTCC substrate. As a result the complete formation of lead-niobium-based pyrochlore phase in active layer is observed. In order to hinder intensive chemical interactions between LTCC components and PMN-PT active layer, lead-zirconate-titanate (PZT) barrier layer was deposited between LTCC substrate and the gold electrode. The results show that after sintering at 850 oC the thick film-layer consists of single phase perovskite PMN-PT ceramic. The deposited barrier layer successfully suppresses the diffusion of PbO into LTCC and SiO2 into active layer. With using PZT barrier layer the dielectric and ferroelectric properties of PMN-PT are significantly improved compared to those of PMN-PT without barrier layer even though they are lower to that on alumina substrate. The procedure for the processing of PMN-PT on barrier-LTCC substrate needs to be optimised to improve the functional response.|
Jozef Stefan Institute