Ultrahigh-temperature piezoelectric polycrystalline ceramics: dramatically enhanced ferroelectricity, piezoelectricity and electrical resistivity in Ca<sub>1−3<i>x</i></sub>Bi<sub>2+3<i>x</i></sub>Nb<sub>2−<i>x</i></sub>Mn<i><sub>x</sub></i>O<sub>9</sub>
Materials research letters