Low-temperature Sintering of LiBxAl1-xSi2O6 Microwave Dielectric Ceramics with Ultra-low Permittivity

doi:10.15541/jim20240494

Abstract

Abstract:

The lithium-based silicate microwave dielectric ceramics with ultra-low permittivity show great potential as substrate materials in the fifth-generation wireless communication technology. However, the residual stress caused by higher sintering temperatures leads to increased dielectric loss, thereby deteriorating the microwave dielectric performance. In this work, B³⁺ was introduced into LiAlSi₂O₆ ceramics to reduce Al³⁺ content, aiming to improve their sintering temperature and microwave dielectric performance. LiB_xAl_1-_xSi₂O₆ (0≤x≤0.20) microwave dielectric ceramics were prepared using a combination of solid-state reaction and cold isostatic pressing techniques. Effects of B³⁺ doping on the sintering characteristics, phase structure, microstructure, and microwave dielectric properties of the materials were characterized. The results show that with a gradual increase in the doping concentration, sintering temperature of the ceramics decreases significantly from 1400 to 1000 ℃. Meanwhile, the relative permittivity (ε_r) decreases from 3.95 to 3.69, the quality factor (Q×f) increases significantly from 24300 to 30560 GHz, and the temperature coefficient of resonant frequency (τ_f) increases from -45.9×10^-6 to -20.9×10^-6 ℃^-1. Specifically, the change in ε_r is mainly influenced by intrinsic polarization, lattice vibrations, and covalent bond strength of the material; the improvement in Q×f is closely related to the increase in packing fraction (PF) and the decrease in damping coefficient; the increase in τ_f is strongly correlated with the bond valence of oxygen (V_O). Furthermore, the composition with x = 0.20 exhibits the best microwave dielectric performance with ε_r = 3.69, Q×f = 30560 GHz, and τ_f = -20.9×10^-6 ℃^-1. Findings of this study on LiB_xAl_1-_xSi₂O₆ provide important theoretical guidance and practical insights for development and application of high-performance microwave dielectric ceramics in the future.

Key words: ultra-low permittivity, lithium aluminum silicate, microwave dielectric property

CLC Number:

TQ174

XIONG Siyu, MO Chen, ZHU Xiaowei, ZHU Guobin, CHEN Deqin, LIU Laijun, SHI Xiaodong, LI Chunchun. Low-temperature Sintering of LiB_xAl_1-_xSi₂O₆ Microwave Dielectric Ceramics with Ultra-low Permittivity[J]. Journal of Inorganic Materials, 2025, 40(5): 536-544.

Figures/Tables 10

Fig. 1 Crystal structure of LiAlSi2O6

Fig. 2 XRD patterns of LiBxAl1-xSi2O6 ceramics (a) At the optimum sintering temperature; (b-d) Rietveld refinement fitting patterns at (b) x = 0, (c) x = 0.12, and (d) x = 0.20

Table 1 Rietveld refined structural parameters of LiBxAl1-xSi2O6 ceramics

x	Lattice parameter				$R p$ /%	$R wp$ /%	χ²
x	a/nm	b/nm	c/nm	V/nm³	$R p$ /%	$R wp$ /%	χ²
0	0.75380(5)	0.75380(5)	0.91556(4)	0.52024(4)	7.69	10.8	1.84
0.05	0.75346(3)	0.75346(3)	0.91533(1)	0.51963(9)	7.32	10.1	1.83
0.08	0.75320(5)	0.75320(5)	0.91494(0)	0.51906(2)	7.24	10.2	1.89
0.12	0.75286(8)	0.75286(8)	0.91434(9)	0.51826(2)	7.24	10.2	1.87
0.16	0.75246(2)	0.75246(2)	0.91332(8)	0.51712(5)	7.29	10.1	1.86
0.20	0.75206(4)	0.75206(4)	0.91257(9)	0.51615(5)	7.22	9.98	1.87

Table 1 Rietveld refined structural parameters of LiBxAl1-xSi2O6 ceramics

x	Lattice parameter				$R p$ /%	$R wp$ /%	χ²
x	a/nm	b/nm	c/nm	V/nm³	$R p$ /%	$R wp$ /%	χ²
0	0.75380(5)	0.75380(5)	0.91556(4)	0.52024(4)	7.69	10.8	1.84
0.05	0.75346(3)	0.75346(3)	0.91533(1)	0.51963(9)	7.32	10.1	1.83
0.08	0.75320(5)	0.75320(5)	0.91494(0)	0.51906(2)	7.24	10.2	1.89
0.12	0.75286(8)	0.75286(8)	0.91434(9)	0.51826(2)	7.24	10.2	1.87
0.16	0.75246(2)	0.75246(2)	0.91332(8)	0.51712(5)	7.29	10.1	1.86
0.20	0.75206(4)	0.75206(4)	0.91257(9)	0.51615(5)	7.22	9.98	1.87

Fig. 3 Relationship between bulk density and sintering temperature of LiBxAl1-xSi2O6 ceramics (a) LiAlSi2O6 ceramic; (b) LiBxAl1-xSi2O6 ceramic; (c) Bulk density and sintering temperature varied with x

Fig. 4 SEM images and grain size distributions of LiBxAl1-xSi2O6 ceramics (a) x = 0; (b) x = 0.05; (c) x = 0.08; (d) x = 0.12; (e) x = 0.16; (f) x = 0.20

Fig. 5 Raman spectra and corresponding parameters of LiBxAl1-xSi2O6 ceramics (a) Raman spectra at different compositions; (b) Raman shift and FWHM at 493 cm-1 changed with composition

Fig. 6 Microwave dielectric properties of LiBxAl1-xSi2O6 ceramics (a) εr and εcorr; (b) Q×f and PF; (c) τf and VO

Table 2 Vm, α, εtheo, εr, and α/Vm of LiBxAl1-xSi2O6 ceramics

x	V_m / nm³	α / nm³	ε_theo	ε_r	α·V_m^-1
0	0.1300610	0.0157900	4.1042	3.95	0.121405
0.05	0.1299098	0.0157530	4.0968	3.90	0.121261
0.08	0.1297655	0.0157308	4.0949	3.85	0.121225
0.12	0.1295655	0.0157012	4.0928	3.81	0.121184
0.16	0.1292813	0.0156716	4.0947	3.76	0.121221
0.20	0.1290388	0.0156420	4.0946	3.69	0.121219

Table 3 Bond valence, covalence and average covalence of LiBxAl1-xSi2O6 ceramics

x	V_Li	V_Si/Al	V_O	C_Li-O/%	C_Si/Al-O/%	Average/%
0	0.820	3.906	1.912	18.87	53.18	36.03
0.05	0.821	3.935	1.924	18.89	53.44	36.16
0.08	0.823	3.947	1.930	18.92	53.54	36.23
0.12	0.824	3.978	1.943	18.94	53.81	36.37
0.16	0.825	4.036	1.968	18.95	54.31	36.63
0.20	0.829	4.075	1.986	19.02	54.65	36.83

Table 4 Sintering temperatures (ST) and microwave dielectric properties of several silicates compared with LiBxAl1-xSi2O6[17,19,26,28,38,41 -45]

Component	ST/℃	ε_r	Q×f/GHz	τ_f/(×10^-6, ℃^-1)	Ref.
LiAlSiO₄	1350	4.9	36000	-57.3	[17]
Li(Al_0.99Li_0.01)SiO_3.99	1250	3.49	51358	-51.48	[17]
Ca₂SiO₄	1450	8.6	26100	-89	[19]
Sr₂SiO₄	1575	9.5	19100	-205	[19]
Ba₂SiO₄	1525	13.1	17900	-17	[19]
Zn₂SiO₄	1340	5.7	53000	-16	[41]
Ba₂ZnSi₂O₇	1200	8.09	26600	-51.4	[42]
Sr₂MgSi₂O₇	1280	6.85	22530	-32	[43]
Sr₃MgSi₂O₈	1450	11.6	25375	-57.41	[44]
Li₂SiO₃	1025	6.19	30550	-40.95	[38]
Li₂ZnSiO₄	1250	5.8	14700	-96.6	[45]
Li₂MgSiO₄	1100	5.73	13570	-16.7	[26]
LiB_xAl_1-_xSiO₄(0.02≤x≤0.1)	875-1100	3.34-3.73	25770-27540	-22.85--16.5	[28]
LiB_xAl_1-_xSi₂O₆(0≤x≤0.20)	1000-1400	3.69-3.95	24300-30500	-45.9--20.9	This work

References 45

[1]	ZHOU D, PANG L X, WANG D W, et al. High permittivity and low loss microwave dielectrics suitable for 5G resonators and low temperature co-fired ceramic architecture. Journal of Materials Chemistry C, 2017, 5(38): 10094.
[2]	XIONG Y, XIE H Y, RAO Z G, et al. Compositional modulation in ZnGa₂O₄ via Zn²⁺/Ge⁴⁺ co-doping to simultaneously lower sintering temperature and improve microwave dielectric properties. Journal of Advanced Ceramics, 2021, 10(6): 1360.
[3]	LIN Q B, SONG K X, LIU B, et al. Vibrational spectroscopy and microwave dielectric properties of AY₂Si₃O₁₀ (A = Sr, Ba) ceramics for 5G applications. Ceramics International, 2020, 46(1): 1171.
[4]	CHEN D Q, YAN N, CAO X F, et al. Entropy regulation in LaNbO₄-based fergusonite to implement high-temperature phase transition and promising dielectric properties. Journal of Advanced Ceramics, 2023, 12(5): 1067.
[5]	ZHANG P, ZHAO Y G. Influence of Sm³⁺ substitutions for Nd³⁺ on the microwave dielectric properties of (Nd_1-_xSm_x)NbO₄ (x = 0.02-0.15) ceramics. Journal of Alloys and Compounds, 2016, 654: 240.
[6]	JABEEN S, KHAN Q U. An integrated MIMO antenna design for Sub-6 GHz & millimeter-wave applications with high isolation. AEU-International Journal of Electronics and Communications, 2022, 153: 154247.
[7]	LOU W C, MAO M M, SONG K X, et al. Low permittivity cordierite-based microwave dielectric ceramics for 5G/6G telecommunications. Journal of the European Ceramic Society, 2022, 42(6): 2820.
[8]	XIONG S Y, CHEN D Q, ZHU X W, et al. Processing strategy and composite regulation on dielectric performance in Li₂O-Al₂O₃-B₂O₃ dielectric systems using SrTiO₃. Journal of the American Ceramic Society, 2024, 107(9): 6080.
[9]	WU F F, ZHOU D, DU C, et al. Design of a Sub-6 GHz dielectric resonator antenna with novel temperature-stabilized (Sm_1-_xBi_x)NbO₄ (x = 0-0.15) microwave dielectric ceramics. ACS Applied Materials & Interfaces, 2022, 14(5): 7030.
[10]	LIU B, HU C C, HUANG Y H, et al. Crystal structure, infrared reflectivity spectra and microwave dielectric properties of CaAl₂O₄ ceramics with low permittivity. Journal of Alloys and Compounds, 2019, 791: 1033.
[11]	LIU B, LIU X Q, CHEN X M. Sr₂LaAlTiO₇: a new Ruddlesden- Popper compound with excellent microwave dielectric properties. Journal of Materials Chemistry C, 2016, 4(8): 1720.
[12]	JIANG C, WU S P, MA Q, et al. Synthesis and microwave dielectric properties of Nd₂SiO₅ ceramics. Journal of Alloys and Compounds, 2012, 544: 141.
[13]	ZOU Z Y, CHEN Z H, LAN X K, et al. Weak ferroelectricity and low-permittivity microwave dielectric properties of Ba₂Zn₍₁₊_x₎Si₂O₍₇₊_x₎ ceramics. Journal of the European Ceramic Society, 2017, 37(9): 3065.
[14]	KRZMANC M M, VALANT M, JANCAR B, et al. Sub-solidus synthesis and microwave dielectric characterization of plagioclase feldspars. Journal of the American Ceramic Society, 2005, 88(9): 2472.
[15]	SONG X Q, LEI W, ZHOU Y Y, et al. Ultra-low fired fluoride composite microwave dielectric ceramics and their application for BaCuSi₂O₆-based LTCC. Journal of the American Ceramic Society, 2020, 103(2): 1140.
[16]	HUANG L, DING S H, YAN X K, et al. Structure and microwave dielectric properties of BaAl₂Si₂O₈ ceramic with Li₂O-B₂O₃ sintering additive. Journal of Alloys and Compounds, 2020, 820: 153100.
[17]	WANG Y R, DING S H, HOU Z P, et al. Structure and microwave dielectric properties of Li(Al_1-_xLi_x)SiO_4-_x ceramics. Ceramics International, 2023, 49(3): 4290.
[18]	KWEON S H, JOUNG M R, KIM J S, et al. Low temperature sintering and microwave dielectric properties of B₂O₃-added LiAlSiO₄ ceramics. Journal of the American Ceramic Society, 2011, 94(7): 1995.
[19]	JOSEPH T, SEBASTIAN M T. Microwave dielectric properties of alkaline earth orthosilicates M₂SiO₄ (M = Ba, Sr, Ca). Materials Letters, 2011, 65(5): 891.
[20]	PELLETANT A, REVERON H, CHÊVALIER J, et al. Grain size dependence of pure β-eucryptite thermal expansion coefficient. Materials Letters, 2012, 66(1): 68.
[21]	FERRAZ R F, PEREIRA M D C, OLIVEIRA R A P. Synthesis and characterization of β-spodumene by a new Sol-Gel route assisted by whey protein. Journal of Sol-Gel Science and Technology, 2024, 111(3): 718.
[22]	WELSCH A M, MURAWSKI D, PREKAJSKI M, et al. Ionic conductivity in single-crystal LiAlSi₂O₆: influence of structure on lithium mobility. Physics and Chemistry of Minerals, 2015, 42(5): 413.
[23]	WELSCH A M, BEHRENS H, ROSS S, et al. Structural control of ionic conductivity in LiAlSi₂O₆ and LiAlSi₄O₁₀ glasses and single crystals. Zeitschrift für Physikalische Chemie, 2012, 226(5/6): 491.
[24]	SHOU H W, DUAN Y H. Anisotropic elasticity and thermal conductivities of (α, β, γ)-LiAlSi₂O₆ from the first-principles calculation. Journal of Alloys and Compounds, 2018, 756: 40.
[25]	LI C C, XIANG H C, YIN C Z, et al. Ultra-low loss microwave dielectric ceramic Li₂Mg₂TiO₅ and low-temperature firing via B₂O₃ addition. Journal of Electronic Materials, 2018, 47(11): 6383.
[26]	PENG R, LI Y X, SU H, et al. Effect of cobalt-doping on the dielectric properties and densification temperature of Li₂MgSiO₄ ceramic: calculation and experiment. Journal of Alloys and Compounds, 2020, 827: 154162.
[27]	PENG R, LI Y X, TANG X L, et al. Improved sintering and microwave dielectric properties of Li₂CaSiO₄ ceramic with magnesium atom substitution. Ceramics International, 2020, 46(7): 8869.
[28]	XIONG S Y, ZHU G B, ZHU X W, et al. Microstrip dielectric patch antenna fabrication and characterization using ultra low permittivity and low temperature Co-fired LiAlSiO₄ ceramics. Journal of the European Ceramic Society, 2025, 45(2): 116930.
[29]	LI C, DING S H, SONG T X, et al. Structure and microwave dielectric properties of BaAl_2-2_xLi₂_xSi₂O_8-2_x ceramics. Ceramics International, 2021, 47(4): 4895.
[30]	SHANNON R D. Dielectric polarizabilities of ions in oxides and fluorides. Journal of Applied Physics, 1993, 73(1): 348.
[31]	YIN C Z, DU K, ZHANG M, et al. Novel low-ε_r and lightweight LiBO₂ microwave dielectric ceramics with good chemical compatibility with silver. Journal of the European Ceramic Society, 2022, 42(11): 4580.
[32]	XING Z, YIN C Z, YU Z Z, et al. Synthesis of LiBGeO₄ using compositional design and its dielectric behaviors at RF and microwave frequencies. Ceramics International, 2020, 46(14): 22460.
[33]	SHANNON R D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallographica Section A, 1976, 32(5): 751.
[34]	YOON S H, KIM D W, CHO S Y, et al. Investigation of the relations between structure and microwave dielectric properties of divalent metal tungstate compounds. Journal of the European Ceramic Society, 2006, 26(10):2051.
[35]	SU C X, AO L Y, ZHANG Z W, et al. Crystal structure, Raman spectra and microwave dielectric properties of novel temperature- stable LiYbSiO₄ ceramics. Ceramics International, 2020, 46(12): 19996.
[36]	KIM E S, CHUN B S, FREER R, et al. Effects of packing fraction and bond valence on microwave dielectric properties of A²⁺B⁶⁺O₄ (A²⁺: Ca, Pb, Ba; B⁶⁺: Mo, W) ceramics. Journal of the European Ceramic Society, 2010, 30(7): 1731.
[37]	DU Q B, TANG Y, LI J, et al. A low-ε_r and high-Q microwave dielectric ceramic Li₂SrSiO₄ with abnormally low sintering temperature. Journal of the European Ceramic Society, 2021, 41(15): 7678.
[38]	HUANG Y W, YANG X H, ZHANG Y C. Novel single-phase Li₂SiO₃ microwave dielectric ceramic with low permittivity. Journal of the European Ceramic Society, 2025, 45(2): 116940.
[39]	REANEY I M, IDDLES D. Microwave dielectric ceramics for resonators and filters in mobile phone networks. Journal of the American Ceramic Society, 2006, 89(7):2063.
[40]	PARK H S, YOON K H, KIM E S. Effect of bond valence on microwave dielectric properties of complex perovskite ceramics. Materials Chemistry and Physics, 2003, 79(2): 181.
[41]	GUO Y P, OHSATO H, KAKIMOTO K I. Characterization and dielectric behavior of willemite and TiO₂-doped willemite ceramics at millimeter-wave frequency. Journal of the European Ceramic Society, 2006, 26(10): 1827.
[42]	ZOU Z Y, DU K, LAN X K, et al. Anti-reductive characteristics and dielectric loss mechanisms of Ba₂ZnSi₂O₇ microwave dielectric ceramic. Ceramics International, 2019, 45(15): 19415.
[43]	XIAO M, WEI Y S, SUN H R, et al. Crystal structure and microwave dielectric properties of low-permittivity Sr₂MgSi₂O₇ ceramic. Journal of Materials Science: Materials in Electronics, 2018, 29(23): 20339.
[44]	HE Y H, WEI X L, HE G Q, et al. Sintering behavior, phase composition, microstructure, and dielectric properties of low- permittivity alkaline earth silicate Sr₃MgSi₂O₈ ceramics. Journal of Materials Science: Materials in Electronics, 2022, 33(35): 26263.
[45]	DOU G, ZHOU D X, GONG S P, et al. Low temperature sintering and microwave dielectric properties of Li₂ZnSiO₄ ceramics with ZB glass. Journal of Materials Science: Materials in Electronics, 2013, 24(5): 1601.

Low-temperature Sintering of LiB_xAl_1-_xSi₂O₆ Microwave Dielectric Ceramics with Ultra-low Permittivity

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