Successful aqueous processing of a lead free 0.5Ba(Zr_0.2Ti_0.8)O₃–0.5(Ba_0.7Ca_0.3)TiO₃ piezoelectric material composition

Abstract

We report on the successful aqueous processing of a lead free piezoelectric 0.5Ba(Zr 0 2 Ti 0 8 )O 3 0.5(Ba 0 7 Ca 0 3 )TiO 3 (BZT BCT) composition with the final functional properties of the materials unaffected by the various processing steps involved. X-ray diffraction results show a single tetragonal perovskite crystalline phase for the as-received sintered BZT BCT powder. The purity of the perovskite phase for BZT BCT powder was found to be controlled even after ageing the material in water for 24 h as a successful surface treatment against hydrolysis. An aqueous suspension of surface treated BZT BCT powder with 50 vol% solid loading was successfully transformed into micro-sized granules via a freeze granulation (FG) method. Various structural, electrical and mechanical properties of sintered BZT BCT-FG and BZT BCT-NG ceramics consolidated from freeze granulated and non-granulated (NG) powders, respectively, were measured. The dielectric constant (3 r ) values of the BZT BCT-FG sample were found to be higher, with lower dielectric loss (tan d) values in comparison with those of a sample prepared from the BZT BCT-NG powder at all temperatures and with all frequency ranges tested.Nanoindentation results revealed that the ability to oppose deformation was nearly 10-fold higher for BZT BCT-FG (6.93 GPa) than for BZT BCT-NG ceramics (543 MPa). The functional properties of BZT BCT-FG samples confirmed the benefits of the aqueous processing approach in comparison with traditional dry pressing. A IntroductionSuccessful aqueous processing of multicomponent electroceramics relies on their various functional properties being unaffected by the chance of there being ionic leaching in water. There have been recent reports in the literature on the sintering behavior of BZT-BCT material showing dielectric properties at various sintering temperatures.8 11 Depending on a material's functional applications, it is necessary to control its structural and compositional evolution to achieve superior properties. Furthermore, the materials need to be consolidated in bulk (polycrystalline ceramics, single crystals) or in lm (thick and thin) form to draw benets from their relevant properties. A reduction in dimension of all passive components without compromising performance, and improved reliability are desirable in electronics technology.To date, non-aqueous processing of electroceramics is preferred because of the common water sensitiveness of the starting powders and the consequent leaching of material components, which affects the nal product functional properties and oen results in exaggerated grain growth and low nal density.12,13 The reason for the detrimental effects of water is believed to be the instability of alkaline-earth titanates in water, which were rst observed experimentally in calcium titanate (CaTiO 3 ).14 However, aqueous processing is attractive from both environmental and economical standpoints. The knowledge acquired with aqueous processing of other water sensitive powders such as magnesium aluminate (M...

Structure and electrical properties of IrO2-doped 0.5Ba0.7Ca0.3TiO3–0.5BaTi0.8Zr0.2O3 ceramics via low-temperature sintering

“…However, the application of BT-based materials is limited by their low Curie temperature (T C ) and single functional performance [4]. To address these issues, many researchers have attempted modification of BT-based materials by doping/substituting elements, broadening their performance capabilities by endowing the materials with optical, electrical, acoustic, or/and magnetic properties [5][6][7][8].…”

Fostering the properties of Zr0.8Sn0.2TiO4 (ZST) ceramics via freeze granulation without sintering additives

“…Such potential gains derived from processing could be a way to exclude sintering additives from Zr 1Àx Sn x TiO 4 compositions. Our recent ndings 15,17,18 stimulated us to achieve the successful aqueous colloidal processing of Zr 1Àx Sn x TiO 4 composition and further prepare high quality spherical granules by freeze granulation (FG), resulting in ceramics with high green dense compact on consolidation. FG can help ceramic manufacturers achieve powder formulations with superior homogeneity, pressing performance and dispersibility.…”

“…An increase in packing efficiency and compact density will enhance the densication ability upon sintering while implying a decrease in total shrinkage. 15,18 This is conrmed by the data plotted in Fig. 6 that compares the dilatometry curves of all types of powder compacts (FG-ZST, NG-ZST and NG-ZST-ZnO) monitored within the temperature range from room temperature (RT) to 1400 C. The FG-ZST curve exhibits a negative inclination along the lower temperature range probably because of the homogeneous distribution of binder among the particles, and its burnout enables the particles to gradually approach each other.…”

Preventing hydrolysis of BaTiO3 powders during aqueous processing and of bulk ceramics after sintering

“…The earlier findings [25][26][27][28][29][30] prepared from dry milled BT and AM BT powders and ultrasonicated for minutes to de-agglomerate the BT particles, followed by particle size distribution measurements.…”

“…Several research works on aqueous processing of BT have reported suspensions with solid loadings up to 40 vol.% with dispersion of powders being achieved via pH variations or by adding dispersing agents. 29,30 Such processing difficulties were successfully overcome through a suitable thermochemical surface treatment given to the powder particles to prevent hydrolysis, improve their dispersion ability in water, increase the solid loadings and enhance colloidal stability, without damaging final properties of the sintered material.…”