By controlling the granulometric distribution of the powders, a density of >96% of the theoretical density has been attained for Ba(Zn 1/3 Ta 2/3 )O 3 that has been sintered at a low temperature (1450°C) for a short soaking time (2 h). Attrition milling produces a very fine and monomodal powder that allows for good densification. The attrition conditions result from a compromise between granulometric distribution and the risk of pollution. We have found a great influence of the origin of the raw materials on the temperature coefficient of frequency, allowing a modulation in the range of 0-15 ppm/°C. Finally, we have studied the influence of each step of the process on the dielectric properties and identified the secondary phases that form with the evaporation of zinc: an eight-layered hexagonal perovskite and a tetragonal tungsten-bronze-type phase.

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The top-seeding melt texture growth (TSMTG) process is investigated in a small-vertical-thermal-gradient furnace in order to better understand the conditions for growing large single-grain pellets. An crystal was used as seed in a Y123 - Y211 composite with additions. It was shown that the role of the seed is to initiate the sympathetic nucleation growth mechanism. Indeed, the additional driving force induced by the seed is clearly demonstrated by a decrease in the undercooling of the system. The seeding crystal introduces a heterogeneous nucleation centre, leading to a very well controlled nucleation rate. Furthermore, we discuss the relation between intrinsic anisotropic growth rate and the processing rate, showing the importance of the thermal conditions of the texturing process to stabilize a sympathetic growth. By careful control of the texturing parameters, we succeeded in producing single-grain pellets as confirmed by a pole figure experiment and neutron diffraction measurements. The levitation force for pellets of 2 cm in diameter reaches 16 N when an NdFeB magnet of the same diameter is used.