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Servo Displacement Transducer Applications
Published in Kenji Uchino, Micro Mechatronics, 2019
The electrostrictive composition (0.45)PMN-(0.36)PT-(0.19)BZN (PMN: lead magnesium niobate, PT: lead titanate, BZN: barium zinc niobate) is used because of its large displacement and small hysteresis. The flapper has a multimorph structure, in which two PMN thin plates are bonded on both sides of a phosphor bronze shim, as shown in Figure 8.24a. The multimorph structure is used for its enhanced tip displacement, generative force, and response speed. The structure is addressed such that the top and bottom electrodes and the metal shim have a common ground potential, as shown in the figure, and a high voltage (designated by V1 and V2 in the figure) is applied on the electrodes between the two PMN plates on each side of the shim. The tip deflection exhibits a quadratic dependence on the applied voltage, as would be expected for an electrostrictive response. Thus, in order to obtain a linear relation, a push-pull driving method is adopted, in which the applied voltages are controlled such that V1=Vo+vappV2=Vo−vapp[Vo=600V]where vapp is the applied signal voltage. A plot of vapp as a function of displacement x, as shown in Figure 8.24b, is seen to be nearly linear. Notice that the displacement hysteresis for the PMN-based ceramic is much smaller than what would occur for a PZT piezoelectric. The resonance frequency of this flapper in oil is about 2 kHz.
The Influence of Pb(Mg1/3Nb2/3)O3-doping on the thermoelectric properties of BaTiO3 ceramics
Published in Phase Transitions, 2018
J. Suchanicz, P. Czaja, K. Kluczewska, H. Czternastek, M. Sokolowski, A. Węgrzyn
Thermoelectric materials have attracted attention due to their applications in waste heat recovery and refrigeration. The efficiency of a thermoelectric material can be expressed in terms of a dimensionless quantity called ‘figure of merit’ [1] as given by ZT = σS2T/κ, where σ, S, κ and T indicate electrical conductivity, the Seebeck coefficient, thermal conductivity and absolute temperature, respectively. To obtain a high value figure of merit, one should have a high-power factor (σS2) at low thermal conductivity (κ). Good thermoelectric materials require a rather defective crystal structure in order to reduce phonon scattering and, thereby, to increase the thermoelectric performance. Barium titanate BaTiO3 is one of the widely applied lead-free ferroelectric materials due to a relatively high permittivity and low costs. Lead magnesium-niobate Pb(Mg1/3Nb2/3)O3 belongs to a class of disordered and inhomogeneous materials, i.e. is a classical relaxor. Pure BaTiO3 has rather small thermoelectric efficiency. It is expected that PMN incorporation to BT can improve thermoelectric efficiency due to an increase in the degree of A and B-site disorder owing to the presence of Pb2+ and (Mg, Nb)4+ ions.