Structural Transitions and Microwave Dielectric Properties of Ba_2−2xSr_2xSmSbO₆ Double Perovskites

Abstract

Structures and microwave dielectric properties of Ba2−2xSr2xSmSbO6 (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 Ba2−2xSr2xSmSbO6 system via the sequence: Fm‐3m → I2/m → P21/n. Dielectric properties of the ceramics were measured at microwave frequencies (9–11 GHz). With the increase of x, the dielectric constant (εr) 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 (τf) decreases from +25 to −50 ppm/°C. The relationships between composition, structure, and microwave dielectric properties in Ba2−2xSr2xSmSbO6 were discussed from the phase transition consideration.

The latest process and challenges of microwave dielectric ceramics based on pseudo phase diagrams

“…The structural studies of A 2 B′B″O 6 (A = Ba, Sr, Ca; B′ = lanthanide, Mg, Cr, Bi; B″ = Nb, Ta, Sb, W) indicated that phase transitions were ascribed to the tilting of B′O 6 /B″O 6 . In the Ba 2-2x Sr 2x SmSbO 6 system, phase transitions of Fm3m, I 2 /m, and P2 1 /n were observed and the τ f value shifted from +25 to -50 ppm/ [473]. Effect of non ℃ stoichiometry Ba 1+x (MgW) 1/2 O 3 , Ba(Mg 1+y W) 1/2 O 3 , and Ba(MgW 1+z ) 1/2 O 3 and the sintering temperature on microwave dielectric properties was systematically investigated by Wu and Bian [474] and Chen et al [475], respectively.…”

Lattice dynamics and phonon characteristics of complex perovskite microwave ceramics

“…The angle θ is the phase change on reflection, and by knowing R ω c and θ ω c , n and R can be calculated from (15) and (16) [107]. The value of θ at any frequency ω c is not isolated, while it is directly interrelated with the reflection spectra by the integral transform.…”

“…1, pp. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] This is an open access article published by the IET under the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/) the complex nature of the atoms in the B-site promotes the splitting of the vibrational modes, leading to a more complicated IR spectrum.…”

“…By now, a series of MWDCs with a range of permittivities have been developed as follows: (i) (Mg,Zn)TiO 3 , for ɛ r ∼ 20, (ii) ‐type ( A = Ba, Sr; B ′ = Mg, Zn,…; B ″ = Nb, Ta), for ɛ r ∼ 30–40, (iii) (Sr,Ca)TiO 3 –(La,Nd)AlO 3 , BaTi 4 O 9 , and Ba 2 Ti 9 O 20 , for ɛ r ∼ 40–45, (v) BaO–Ln 2 O 3 –TiO 2 (Ln = La, Nb, Sm) for ɛ r > 70, etc . [12–27]. Among these MWDCs, the ‐type complex perovskite ceramics has two different oxidation state elements on the B‐sites, i.e.…”

Crystal structure and X-ray photoemission spectroscopic study of A2LaMO6 [A=Ba, Ca; M=Nb, Ta]

“…In this regard DPOs having rare-earth and d 0 transition metal as B-site and alkaline earth element as A-site cation are widely studied for microwave resonators, filters etc. [5][6][7][8][9][10]. Among them much attention has been paid to Ba 2 LnMO 6 and Sr 2 LnMO 6 [Ln: lanthanides, M: Nb, Ta] families [5,6].…”