Structural Transitions and Microwave Dielectric Properties of <scp> <scp>Ba</scp> </scp> _{2−2 <i>x</i>} <scp> <scp>Sr</scp> </scp> _{2 <i>x</i>} <scp> <scp>SmSbO</scp> </scp> ₆ Double Perovskites

Abstract

Structures and microwave dielectric properties of Ba 2−2 x Sr 2 x SmSbO 6 ( x = 0–1) ceramics were studied in this article. The phase transitions were analyzed using X‐ray powder diffraction, transmission electron microscopy, and Raman spectroscopy. All structures are proved to be ordered double perovskites, and a series of composition‐induced phase transitions are confirmed in the Ba 2−2 x Sr 2 x SmSbO 6 system via the sequence: Fm‐3m → I2/m → P2 1 /n. Dielectric properties of the ceramics were measured at microwave frequencies (9–11 GHz). With the increase of x , the dielectric constant (ε r ) varies gradually from 20.7 to 16.0, the quality factor ( Q × f ) decreases first from 86 500 GHz to a minimum value at x = 0.4 and then increases slightly to 93 000 GHz, and the temperature coefficient of resonant frequency (τ f ) decreases from +25 to −50 ppm/°C. The relationships between composition, structure, and microwave dielectric properties in Ba 2−2 x Sr 2x SmSbO 6 were discussed from the phase transition consideration.