Phase transition regulation and piezoelectric performance optimization of fresnoite crystal for high temperature acceleration sensing

Fresnoite crystal, Ba2TiSi2O8 (BTS), is a potential candidate for high temperature piezoelectric sensing applications, due to high electrical resistivity and strong piezoelectric response at elevated temperatures. However, anomalies of electro-elastic properties due to phase transition limit its application over a broad temperature range. In this study, a series of strontium substitution crystals, Ba2-xSrxTi2Si2O8 (x=0, 0.2, 0.4 and 0.6), were designed and grown by using the Czochralski pulling method. The phase transition was investigated using Brillouin scattering spectroscopy and single crystal X-ray diffraction, where the observed acoustic anomalies showed softening behavior of the longitudinal acoustic phonon mode accounting for the phase transition of BTS crystal. The bond valance sum was analyzed and demonstrated that Sr substitution can significantly improve the “underbonding” of interlayer Ba cations. The phase transition regulation and piezoelectric activity optimization were realized by Sr substitution. Results confirm that Sr substitution can significantly increase the phase transition temperature and weaken the effect of phase transition on the macroscopic electrical properties. Finally, a shear-mode prototype acceleration sensor with stable sensing performance up to 600oC was achieved.