Bright Upconversion Emission, Increased <i>T</i> _c , Enhanced Ferroelectric and Piezoelectric Properties in <scp> <scp>E</scp> </scp> r‐Doped <scp> <scp>Ca</scp> <scp>Bi</scp> </scp> ₄ <scp> <scp>Ti</scp> </scp> ₄ <scp> <scp>O</scp> </scp> ₁₅ Multifunctional Ferroelectric Oxides

Abstract

Er 3+ ‐doped Ca Bi 4 Ti 4 O 15 ( CBT ) bismuth layer structured ferroelectric ceramics were synthesized by the solid state method. Photoluminescence (UC), dielectric, ferroelectric, and piezoelectric properties were systematically studied for the first time. The Er 3+ ‐doped CBT sample showed a bright up‐conversion UC while simultaneously obtaining an increased Curie temperature ( T c ), enhanced ferroelectric and piezoelectric properties. The UC properties of Er 3+ ‐doped CBT were investigated as a function of Er 3+ concentration and incident pump power. A bright green (556 nm) and a weak red (674 nm) emission bands were obtained under excitation (980 nm) at room temperature, which correspond to the transitions from 4 S 3/2, and 4 F 9/2 to 4 I 15/2 , respectively. The dependence of UC emission intensity on pumping power indicated that three‐photon and two‐photon processes are involved in the green and red UC emission, respectively. Studies on dielectric properties indicated that the introduction of Er increased the T c with relatively smaller values of dielectric loss of CBT , thus making this ceramic suitable for sensor applications at higher temperatures. Ferroelectric and piezoelectric measurements showed that the Er 3+ ‐doped ceramics showed an increase in remnant polarization and piezoelectric constant. As a multifunctional material, Er ‐doped CBT ferroelectric oxide showed great potential in sensor, optical‐electro integration, and coupling device applications.