Effect of V5+ Substitution on Microstructure and Microwave Dielectric Properties of LaTaO4 Ceramics

doi:10.15541/jim20240482

Abstract

Abstract:

Microwave dielectric ceramics are essential materials for 5G/6G communication technology and are primarily employed in fabrication of electronic components such as resonators, filters and dielectric substrates. With the increasing frequency of wireless mobile communication, it is necessary to develop microwave dielectric ceramics with higher quality factor (Q) and near-zero temperature coefficient of resonance frequency (τ_f), thus effectively compensating for rapid attenuation of high-frequency signals in transmission process and enhancing stability of their operation. Consequently, La(Ta_1-_xV_x)O₄ (LTV-x, 0≤x≤0.4) ceramics were prepared by solid-phase sintering. The structure and dielectric properties of ceramics were investigated using crystal structure refinement, transmission electron microscopy and microwave dielectric property measurements. Two specific compositions of La(Ta_1-_xV_x)O₄ ceramics with excellent microwave dielectric properties were synthesized in this system, namely LTV-0.3 (relative dielectric constant ε_r=22.15, Q×f=90100 GHz, τ_f=-9.52×10^-6 ℃^-1) and LTV-0.4 (ε_r=21.75, Q×f=84100 GHz, τ_f=-4.50×10^-6 ℃^-1) ceramics. Results indicate that V⁵⁺ substitution induces the phase transition of LaTaO₄from monoclinic (P21/c) to orthorhombic (Cmc21) phases, while the phase transition temperature is effectively reduced. Their ε_r and τ_f values decrease with increasing x due to phase transition. The Q×f values are influenced not only by relative density but also by packing fraction of the unit cell. Considering their low loss and good temperature stability, these ceramic materials demonstrate promising potential for applications in mobile communication base stations, satellite navigation and radar communication technologies.

Key words: LaTaO₄, microwave dielectric property, temperature coefficient of resonance frequency, ionic substitution, packing fraction

CLC Number:

TQ174

LI Wenyuan, XU Jianan, DENG Han'ao, CHANG Aimin, ZHANG Bo. Effect of V⁵⁺ Substitution on Microstructure and Microwave Dielectric Properties of LaTaO₄ Ceramics[J]. Journal of Inorganic Materials, 2025, 40(6): 697-703.

Figures/Tables 6

Fig. 1 XRD patterns (a) and Rietveld refinement XRD patterns (b-f) of LTV-x ceramics sintered at 1400 ℃ for 4 h

Fig. 2 SEM images of LTV-x ceramics and EDS mappings of area A (a-e) SEM images of LTV-x ceramics (x=(a) 0, (b) 0.1, (c) 0.2, (d) 0.3, (e) 0.4); (f) Variation of grain size as a function of composition; (g-j) EDS mappings of area A in (d)

Fig. 3 TEM and HRTEM characterizations of LTV-0.3 ceramics (a, b) TEM images; (a1, b1) SAED patterns corresponding to area 1 and 2; (a2, b2) HRTEM images of orthorhombic-phase LaTaO4 and monoclinic-phase LaVO4 corresponding to area Ⅰ and Ⅱ

Fig. 4 Apparent densities of LTV-x ceramics sintered at different temperatures and relative densities of ceramics sintered at 1400 ℃

Fig. 5 Microwave dielectric properties of LTV-x ceramics sintered at 1400 ℃ (a) Permittivity (εr: measured; εtheo: calculated by Shannon’s additive rule and Clausius-Mossotti relation; εcor: modified by Bosman and Havinga correction); (b) Q×f, relative density, and packing fraction; (c) Evolution of τf as a functions of x for LTV-x ceramics

Table S1 Lattice parameters and reliable factors of LTV-x ceramics obtained by the Rietveld profile refinement method

x	Atom	Atom position			Mult	Occupancy	Refining reliability factor		Volume/Å³
x	Atom	x	y	z	Mult	Occupancy	R_wp/%	R_p/%	Volume/Å³
0	La1	0.0000	0.6292	0.2500	4	1.0000	8.45	6.18	326.04
	Ta1	0.0000	0.1036	0.2500	4	1.0000
	O1	0.1460	0.2042	0.1572	8	1.0000
	O2	0.2624	0.4663	0.3170	8	1.0000
0.1	La1	0.0000	0.6292	0.2500	4	1.0000	7.54	5.71	325.41
	Ta1	0.0000	0.1036	0.2500	4	0.9000
	V1	0.0000	0.1036	0.2500	4	0.1000
	O1	0.1460	0.2042	0.1572	8	1.0000
	O2	0.2624	0.4663	0.3170	8	1.0000
0.2	La1	0.0000	0.6292	0.2500	4	1.0000	8.62	6.42	324.98
	Ta1	0.0000	0.1036	0.2500	4	0.8000
	V1	0.0000	0.1036	0.2500	4	0.2000
	O1	0.1460	0.2042	0.1572	8	1.0000
	O2	0.2624	0.4663	0.3170	8	1.0000
0.3	La1	0.0000	0.6292	0.2500	4	1.0000	7.39	5.97	323.85
	Ta1	0.0000	0.1036	0.2500	4	0.7000
	V1	0.0000	0.1036	0.2500	4	0.3000
	O1	0.1460	0.2042	0.1572	8	1.0000
	O2	0.2624	0.4663	0.3170	8	1.0000
0.4	La1	0.0000	0.6292	0.2500	4	1.0000	9.27	7.24	323.61
	Ta1	0.0000	0.1036	0.2500	4	0.6000
	V1	0.0000	0.1036	0.2500	4	0.4000
	O1	0.1460	0.2042	0.1572	8	1.0000
	O2	0.2624	0.4663	0.3170	8	1.0000

References 26

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Effect of V⁵⁺ Substitution on Microstructure and Microwave Dielectric Properties of LaTaO₄ Ceramics

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