Fabrication and properties of low temperature sintered PZT-PMN films
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Fabrication and properties of low temperature sintered PZT-PMN films Eugene Stytsenko and Marc Daglish Ceramics, Industrial Research Limited, 69 Gracefield Road, Gracefield Wellington, New Zealand ABSTRACT A film of PZT-PMN composition was fabricated by the deposition of fine powder entrained in airflow on to a substrate at the temperature of 20 0C. The particle flow generated by a jet mill desintegrator circulated inside the cylindrical substrate tube producing a build up on the internal surface of the cylinder. The resulting film, 70 – 150 µm thick was mechanically removed (delaminated) from the substrate and sintered at 800 0C. Microscopic examination of the green and sintered films revealed a very dense microstructure with a grain size for the sintered film of 0.2 – 0.8 µm. The relative permittivity at 1 kHz was about 100 before sintering and 2000 after sintering (unpoled). The permittivity of the sintered film had the same value as for bulk ceramic samples fabricated from the same powder using conventional isostatic pressing technique and sintered at 1250 0C to 97 % of the theoretical density. The study showed that the properties of the green body produced by the powder deposition process were superior to the properties of bulk samples prepared by the conventional pressing procedure. The method provides a route for the formation of a fine grain microstructure, and a sintering temperature 450 0C lower than the accepted sintering temperature for this PZT-PMN composition.
INTRODUCTION Lead-based ferroelectric and relaxor dielectric ceramics have been extensively exploited in commercial applications for more than 50 years. Shaped piezoelectric ceramics account for the largest usage to-date, finding application in a range of sensing, positioning and sonic devices including sonar. More recently there has been an increased demand for multilayer actuating devices with the prospect of substantial growth in the market if the cost of production can be reduced. Using conventional techniques temperatures in excess of 1000 0C are needed to sinter acceptably dense ceramics and layer structures. Reducing the fabrication temperature would allow: • compatibility with less expensive co-fired metallisations, • lower energy costs, • direct deposition of piezoelectric materials on less refractory substrates, and • lower lead emissions. It is perhaps surprising that the accepted sintering temperatures of lead-based electroceramics are only about 100 0C lower than their respective melting points. In comparison with other oxide ceramic systems these temperatures appear to be rather high, which suggests significant reductions in sintering temperature should be possible. In this paper a method is described which demonstrates that by controlling the powder preparation and compaction dense lead-based ceramic bodies can be prepared at 800 0C. F10.5.1
SAMPLE FABRICATION PROCEDURE A PZT – PMN composition used for sample preparation was similar to one described in (1). Raw materials were hatched according to the following formula: [Pb0.95Ba
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