Abstract
Because of their characteristics, including a d33 of 10–15 pC/N and high stability up to temperatures over 1000 °C, polar glass–ceramics containing fresnoite crystals can be regarded as highly effective materials for applications requiring piezoelectricity at high temperatures. In the present paper we investigate barium substitutions in an Sr-fresnoite (STS) glass–ceramic. Two aspects are studied: first, the effect of the substitution on the preferential orientation of the crystallization, and second, the ability of the glass–ceramics to generate and propagate surface acoustic waves (SAW) at high temperatures. XRD analyses show that a 10 at.% substitution of Ba allows us to keep a strong preferential orientation of the (00l) planes of the fresnoite crystals down to more than 1 mm below the surfaces. Higher substitution levels (25 and 50 at.%), induce a non-oriented volume crystallization mechanism that competes with the surface mechanism. SAW devices were fabricated from glass–ceramic substrates with 0, 10 and 25 at.% Ba substitutions. Temperature testing reveals the high stability of the frequency and delay for all of these devices. The glass–ceramic with a 10 at.% Ba substitution gives the strongest amplitude of the SAW signal. This is attributed to the high (00l) preferential orientation and the absence of disoriented volume crystallization.
Highlights
In a few decades, piezoelectric materials have conquered many industrial sectors, whether in the military, the automobile, the IT, the medical or the commercial sector [1].Several families of materials show piezoelectricity, but the most commonly encountered is that of the ferroelectric perovskite–type ceramics, such as lead titanate PbTiO3, barium titanate BaTiO3 and lead zirconate titanate Pb(Zrx Ti1−x )O3, known as PZT [2,3].In ferroelectrics, the crystals are divided in polar domains in which all the dipole moments show the same orientation
In a previous paper [31], we demonstrated the ability of an substitutions in an Sr-fresnoite (STS) glass–ceramic to generate and propagate
Characteristics of of Glass–Ceramics noted in in the the introduction, introduction, the the literature literature highlights highlights that that suitable suitable Sr-fresnoite
Summary
Piezoelectric materials have conquered many industrial sectors, whether in the military (hydrophone, depth sensors, security systems, etc.), the automobile (airbag sensors, injectors, etc.), the IT (hard-drive microactuators), the medical (ultrasonic therapy, insulin pumps, image acquisition, fetus heartbeat detection, etc.) or the commercial (resonators for radios/TV, lighters, alarm systems, music instruments, etc.) sector [1]. Many parameters, as1980s, the glass composition, surface state and thermalglass–ceramics based on non-ferroelectric pyroelectric compounds [15,16,17,18] Among these glass–ceramics, some show fresnoite crystals. A preferential orientation of the (002) plans at the surface was observed with all compositions after a single isothermal heat treatment at 900 ◦ C, but only glasses with a low content of K2 O kept this preferential orientation in the bulk down to 2 mm deep On basis of this latter work, Renoirt et al [40] investigated the crystallization of STS from parent glasses belonging to the SrO–TiO2 –SiO2 –Al2 O3 –K2O system. We compare the ability of non-substituted and Ba-substituted glass–ceramics to operate a SAW device at high temperature
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