Ba 8 ZnTa 6 O 24 : a high-Q microwave dielectric from a potentially diverse homologous series

Abstract

The ceramic Ba8ZnTa6O24 has been synthesized in isolation and its dielectric and crystallographic properties characterized. The material affords excellent dielectric properties, with a high unloaded quality factor Qu=20 800 at 3.28 GHz, high relative permittivity εr=29 and a temperature coefficient of resonant frequency τf=29.4 ppm/°C. The crystal structure adopted is complex, comprising mixed cubic and hexagonal perovskite subunits, and contains cation vacancies on the octahedral sites. A second phase with a closely related structure is identified, demonstrating the existence of a family of materials. This structural complexity offers diverse opportunities for substitutions calculated to enhance the figures of merit reported.

Ba8CoNb6O24: A d0 Dielectric Oxide Host Containing Ordered d7 Cation Layers 1.88 nm Apart

“…The eight-layer hexagonal perovskite Ba 8 ZnTa 6 O 24 adopts a (chcc) 2 sequence (an AO 3 layer (B) is described as h if its two neighboring layers are the same (ABA) or c if they are different (ABC)) and has interesting dielectric properties with a moderately high Q of 20 800 at 3.28 GHz (Q = (tan d) À1 ). [6] Our initial investigations on the Nb analogue Ba 8 [5] are absent, the new Nb phase adopts a different eight-layer stacking sequence in which two hexagonal ABA AO 3 layer units are adjacent to each other in an ccchhccc motif ( Figure 1). [7] High-resolution electron microscopy images directly demonstrate that this sequence is adopted without stacking faults (Figure 2 a).…”

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.…”

“…Herein high-Q and negative s f materials including ilmenite MgTiO 3 (e r = 17, Q9f = 160,000 GHz, s f = -50 ppm/°C ) [14], columbite MgNb 2 O 6 (e r = 21.4, Q9f = 93,800 GHz, s f = -70 ppm/°C) [15,16] and cubic perovskite Ba 3 NiTa 2 O 9 (e r = 23, Q9f = 49,700 GHz, s f = -18 ppm/°C) [17] were selected as candidates for compensating the s f of Ba 8 [18] and modified by Courtney [19] using a Agilent N5230A network analyzer. The ceramic surface morphology was examined by using a Hitachi S4800 scanning electron microscopy (SEM).…”

The sintering behavior and microwave dielectric properties of Mg4(Nb,Sb)2O9 ceramics

“…Thus, a number of these materials have been investigated and developed [1][2][3][4][5]. Among which, α-A1 2 O 3 ceramics with corundum structure has a very high Q value (Qf∼300,000 GHz) and low dielectric constant (ɛ∼10), widely used as substrate and IC packaging materials.…”