Super High Curie Point Piezoelectric Ceramics
High-temperature piezoelectric sensing technology is of major importance to the chemical and material processing, automotive, aerospace, and power generating industries. Ferroelectrics are desirable for piezoelectric application below their Curie points. Ferroelectric polycrystalline ceramics have the advantages over piezoelectric/ferroelectric single crystals of lower cost and the possibility to control, by compositional modifications and processing, their properties.
The perovskite-like layer structured (PLS) A2B2O7 materials, including Sr2Nb2O7, Ca2Nb2O7, Nd2Ti2O7 and La2Ti2O7 have possibly the highest Curie points of any materials. Their piezoelectric properties have only been characterized using single crystal samples. Despite more than 30 years of extensive effort, there is still no report on the ferroelectric and piezoelectric properties of their polycrystalline ceramics. To pole these ceramics at high electrical field, highly textured, dense ceramics with high dc electrical resistivity are necessary. The ferroelectric and piezoelectric properties of lead-free Nd2Ti2O7 Sr2Nb2O7, and La2Ti2O7 grain-oriented ceramics prepared by Spark Plasma Sintering (SPS) using a two-step method was reported for the first time here. These results now open up the possibility of studying the ferroelectric/piezoelectric properties of the PLS family of ceramics with super-high Curie points.