Abstract
Crystallization of strontium fresnoite Sr2TiSi2O8 piezoelectric crystals in Sr–Ti–Si–K–Al–O parent glasses is investigated with the aim of showing the influence of composition and crystallization conditions on the microstructure and piezoelectric properties of the resulting glass-ceramic. All the investigated conditions lead to a surface crystallization mechanism that induces a preferential orientation of crystal growth in the glasses. Near the surface, all the glass-ceramics obtained exhibit (002) planes preferentially oriented parallel to their faces. Deeper in the specimens, this preferential orientation is either kept or tilted to (201) after a depth of about 300 µm. The measurement of the charge coefficient d33 of the glass-ceramic highlights that surface crystallization induces mirror symmetry in the polarization. It reaches 11 to 12 pC/N and is not significantly influenced by the preferential orientation (002) or (201). High temperature XRD shows the stability of the fresnoite phase in the glass-ceramics up to 1000 °C. Mechanical characterization of the glass-ceramics by impulse excitation technique (IET) highlights that the softening of the residual glass leads to a progressive decrease of Young’s modulus in the temperature range 600–800 °C. Damping associated to the viscoplastic transition become severe only over 800 °C.
Highlights
Most piezoelectric sensors and actuators used today are based on ferroelectric polycrystalline ceramics
Due to initially randomly distributed polar domains within the ceramic grains, polarization under a high-strength electric field is required to confer macroscopic piezoelectric properties. These ceramics exhibit high piezoelectric performances, but their main drawback is the depolarization occurring over time and with increasing temperature
Results is followed by Impulse Excitation Technique (IET) using an IMCE equipment [19]
Summary
Most piezoelectric sensors and actuators used today are based on ferroelectric polycrystalline ceramics. Due to initially randomly distributed polar domains within the ceramic grains, polarization under a high-strength electric field is required to confer macroscopic piezoelectric properties. These ceramics exhibit high piezoelectric performances, but their main drawback is the depolarization occurring over time and with increasing temperature. The non-ferroelectric behavior is the result of the single domain configuration of the crystals. In the case of polycrystalline ceramics, a preferential orientation of the crystallite’s polar direction needs to be induced during the elaboration process to obtain a macroscopic piezoelectric material. Preferentially oriented microstructures are not achievable through conventional ceramic powder processing, so these phases are usually obtained in single crystals
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