Vol.:(0123456789) 1 3
Journal of Electronic Materials
https://doi.org/10.1007/s11664-021-09334-4
ORIGINAL RESEARCH ARTICLE
Microwave Dielectric Properties of Ba
5
Li
2
W
3
O
15
Ceramic with Excess
Lithium for Dielectric Resonator Antenna Application
N. D. G. Souza
1
· D. V. M. Paiva
1
· S. E. Mazzetto
2
· M. A. S. Silva
3
· A. S. B. Sombra
3
· P. B. A. Fechine
1
Received: 6 July 2021 / Accepted: 5 November 2021
© The Minerals, Metals & Materials Society 2021
Abstract
Ba
5
Li
2
W
3
O
15
(BLWO) electroceramics with diferent amounts of lithium carbonate (10–15%) were synthesized using the
solid-state route. Powder x-ray difraction (PXRD) and Raman spectroscopy showed the presence of the BaWO
4
(BWO)
phase in the samples. The excess lithium in the BLWO matrices contributed to an increase in the BWO phase and improved
the thermal stability. Images obtained by scanning electron microscopy (SEM) showed grains without a well-defned mor-
phology and with a low porosity. The dielectric properties in the microwave (MW) range for the dielectric resonator based
on BLWO were analysed by the Hakki–Coleman and Silva–Fernandes–Sombra methods. The near-zero temperature coef-
fcient of resonant frequency (6.59 ppm°C
−1
) was obtained for the sample synthesized with 15% Li
2
CO
3
. Numerical studies
based on the coefcient of refection (S
11
) and impedance values of the BLWO-based dielectric resonator antennas (DRA)
were also conducted. They agreed well with the experimental results, which indicates that this material can be applied as
an antenna device in the MW range.
|
Keywords Ceramics · perovskite · dielectric resonator antennas · microwave frequencies
Introduction
The production of new materials used in the development
of wireless communication systems, such as electronic
components, flters, and oscillators, has increased consid-
erably in recent years.
1,2
The need for miniaturization of
these devices, which operate in the microwave (MW) range,
has been highlighted; these devices can be designed for a
wide range of applications, such as satellite communication
systems that use dielectric resonator antennas (DRAs).
3,4
Therefore, dielectric materials that have a moderate dielec-
tric constant (10 < ɛ
r
< 30), low dielectric loss (tan δ <
1 × 10
−3
) or a high-quality factor (Q x f), and an almost
zero temperature coefcient of resonant frequency (τ
f
) have
been reported in the literature to meet the requirements for
MW applications.
1,5
A large class of high-quality materials
used for DRAs belongs to the perovskite family. Materi-
als with a complex perovskite crystalline structure can be
used in electronic devices due to their propensity for ionic
substitution.
6–11
Tungstates have attracted attention due to their good die-
lectric properties and chemical stability.
12
Many tungstates,
such as Ca
3
LnW
2
O
12
(Ln = La, Sm),
12
Ca
(1−x)
Sr
x
WO
4
,
13
BiREWO
6
(RE = Y, Gd and Nd),
14
and Sr
3
WO
6
,
15
demon-
strated attractive MW dielectric properties. Among the tung-
states, Ba
5
Li
2
W
3
O
15
(BLWO), which has a hexagonal per-
ovskite-type structure, has been reported to have good MW
dielectric properties with ɛ
r
of 25.4, a high Q x f value of
approximately 39,000 GHz and τ
f
near zero (10 ppm °C
−1
).
16
Thus, this is a good ceramic candidate for MW applications.
Despite presenting satisfactory results as a dielectric
ceramic, BLWO perovskite materials may form a small
amount of the BaWO
4
(BWO) phase. Thus, syntheses
* P. B. A. Fechine
fechine@ufc.br
1
Grupo de Química de Materiais Avançados (GQMat),
Departamento de Química Analítica e Físico-Química,
Universidade Federal do Ceará – UFC, Campus do Pici, CP
12100, Fortaleza, CE CEP 60451-970, Brazil
2
Departamento de Química Orgânica e Inorgânica,
Universidade Federal do Ceará, Campus do Pici, Bl. 940,
Fortaleza, CE 60440-900, Brazil
3
Laboratório de Telecomunicações e Ciência e Engenharia de
Materiais (LOCEM), Departamento de Física, Universidade
Federal do Ceará, Fortaleza, Brazil