Effects of barium substitution on the sintering behavior, dielectric properties of Ca₂Nb₂O₇ferroelectric ceramics

Abstract

Barium-doped Ca 2 Nb 2 O 7 ceramics were prepared in the form of Ca 2Àx Ba x Nb 2 O 7 (0 x 0.6) by solid-state reaction. The solubility limit of barium in Ca 2 Nb 2 O 7 was found to be x ¼ 0:4 based on X-ray diffraction and Raman spectroscopy analysis. When x 0.4, Ca 2Àx Ba x Nb 2 O 7 solid solutions with a monoclinic perovskites-like layered structure (PLS) were formed, whereas beyond x ¼ 0:4, a secondary phase CaNb 2 O 6 was detected. The dielectric properties obviously depended on the barium substitution. With increasing barium amount, the dielectric constant increased from 33.5 for pure Ca 2 Nb 2 O 7 to 38.6 for x ¼ 0:4 ( f ¼ 1 MHz). The Curie temperature (T c Þ of the x ¼ 0:1 sample was 1280 AE 5 C. The phase transition was confirmed to be the second order.

The Isothermal and Non‐Isothermal Growth Behaviors of Ca2Nb2O7 in Molten Slag

“…[1] The Ca 2 Nb 2 O 7 , with ultra-high Curie temperatures (Tc), possesses good stability performance when the temperature is over 1673 K. [2,3] Ca 2 Nb 2 O 7 also presents an excellent piezoelectric coefficient and electromechanical coupling coefficient. [1,[4][5][6] Besides, Ca 2 Nb 2 O 7 has been applied in the catalysts field, immobilization of nuclear waste field. [1,2,[6][7][8][9][10] In recent years, although Ca 2 Nb 2 O 7 as leadfree piezoelectric material have been studied for different fields, but the investigation of isothermal and non-isothermal growth behaviors of Ca 2 Nb 2 O 7 in the molten slag is infrequent.…”

Ferroelectric domains and luminescent properties of Pr3+‐doped Ca2Nb2O7 ceramics

“…Recently, the perovskite‐like layer structured (PLS) ferroelectric materials with a formula of A n B n O 3n+2 have attracted much attention due to their potential applications for high‐temperature piezoelectric sensors such as in aerospace, petrochemical engineering, and nuclear industry . As a member of the PLS family, Ca 2 Nb 2 O 7 (CNO) is known for its ultrahigh Curie temperature ( T C ~ 1500°C) and its ferroelectricity has been confirmed by the measurement of P ‐ E hysteresis loop, pyroelectric current switching and dielectric properties in past research . CNO belongs to the monoclinic system with space group Pna 2 1 , and it has a large coercive electric field .…”