Dielectric Properties of Ba₄Sm₂Fe₂M₈O₃₀ (M=Nb, Ta) with Tetragonal Bronze Structure

Abstract

The tetragonal tungsten bronze (TTB)‐structured Ba4Sm2Fe2M8O30 (M=Nb, Ta) dielectrics were prepared and investigated. Dielectric and ferroelectric behaviors revealed that the niobate and the tantalate display ferroelectric and paraelectric nature at room temperature (RT), respectively. The dielectric spectrum showed that Ba4Sm2Fe2Ta8O30 ceramic has a high dielectric constant (∼97), a comparatively low temperature coefficient of dielectric constant (∼−105 ppm/°C), and a low dielectric loss (∼10−3) (at 1 MHz). These results indicated that the present tantalate might be a new temperature‐compensating ceramic.

Microwave dielectric properties and low temperature sintering behavior of Li2CoTi3O8 ceramic

“…It is clear that the optimized sintering temperature of the Li 2 CoTi 3 O 8 ceramic (at 1025 • C) is 50 • C lower than those of Li 2 ATi 3 O 8 (A = Zn, Mg) ceramics [18]. The ε r of Li 2 CoTi 3 O 8 ceramic is slightly higher than those of Li 2 ATi 3 O 8 (A = Zn, Mg) ceramics, which may attribute to higher relative density since their average ionic polarizability (˛T D /V m , wherę T D is the sum of ionic polarizability of individual ions, and V m is the molar volume) are near the same(∼0.19) calculated from modified Clausius-Mossotti equation [1,25]. The Q × f and f values are between those of the Li 2 MgTi 3 O 8 and Li 2 ZnTi 3 O 8 ceramics.…”

“…Since the Shannon's effective ionic radii of Co 2+ (0.745Á) are very similar to those of Mg 2+ (0.72Á) and Zn 2+ (0.74Á) [19], and [23][24][25]. Then, the low temperature sintering behavior of Li 2 CoTi 3 O 8 ceramic with the addition of BCB is also reported.…”

Tuning the temperature coefficient of resonant frequency for 8-layer twinned hexagonal perovskite Ba8ZnTa6O24 ceramics

“…Recently, the closely related 8-layer twinned hexagonal perovskite tantalates [7][8][9][10][11][12] were reported to demonstrate good microwave dielectric properties, e.g. Ba 8 Li 2 Ta 6 O 24 [7] and Ba 8 MTa 6 O 24 (M = Zn, Ni, Co, Mg) [8][9][10][11] exhibit modest e r * 27-30, high Q9f * 70,000-100,000 GHz, comparable to the 2:1-ordered complex perovskite resonators. Dense pellets of these hexagonal perovskite dielectrics can be obtained at temperatures significantly lower than the complex perovskites and do not require prolonged annealing to achieve cationic ordering for the high Q.…”

“…For example, 2:1-ordered Ba 3 ZnTa 2 O 9 and Ba 3 MgTa 2 O 9 ceramics have superior Q9f * 100,000-150,000 GHz, being able to offer efficient utilization of the allocated electromagnetic frequency window [3,4]. Recently, the closely related 8-layer twinned hexagonal perovskite tantalates [7][8][9][10][11][12] were reported to demonstrate good microwave dielectric properties, e.g. Ba 8 Li 2 Ta 6 O 24 [7] and Ba 8 MTa 6 O 24 (M = Zn, Ni, Co, Mg) [8][9][10][11] exhibit modest e r * 27-30, high Q9f * 70,000-100,000 GHz, comparable to the 2:1-ordered complex perovskite resonators.…”

Sintering behavior and microwave dielectric properties of LiMVO4 (M = Mg, Zn)

“…It is well accepted that the factors affecting the microwave dielectric properties can be classified into two categories: one is the intrinsic factors such as the lattice vibration and ionic polarization, the other the extrinsic ones including density, pore, secondary phase, and impurities [1,27]. In the present system, the effects from secondary phase and impurities could be eliminated based on the XRD and SEM results that confirmed the formation of single phase ceramics with high relative density ([90 %).…”