Crystal Structure and Terahertz Dielectric Properties of (Ti0.5W0.5)5+ Doped MgNb2O6 Ceramics

doi:10.15541/jim20240512

Abstract

Abstract:

MgNb₂O₆ ceramics offer advantages such as moderate sintering temperature and low dielectric loss, making them widely applicable in the field of wireless communications. However, the correlation mechanism between MgNb₂O₆ structure and terahertz dielectric properties remains inadequately understood. To address this gap, MgNb_2-_x(Ti_0.5W_0.5)_xO₆ (x=0-0.03) ceramics were prepared by solid state reaction method in this study. The crystal structure of MgNb_2-_x(Ti_0.5W_0.5)_xO₆ (x=0-0.03) ceramics and its correlation with terahertz dielectric properties were studied using Rietveld refinement, complex chemical bond theory, and terahertz time domain spectroscopy. The global instability index was introduced to characterize the in-lattice strain in single-phase MgNb₂O₆ system, establishing a correlation among in-lattice strain, lattice energy and terahertz dielectric loss. The results show that (Ti_0.5W_0.5)⁵⁺ ions can modify the crystal structure. With the increase in doping amount, the internal strain reduces, and the stability of crystal structure and lattice energy increases, leading to decrease in dielectric loss. In addition, the atomic packing density increases with higher (Ti_0.5W_0.5)⁵⁺ ion doping, which effectively inhibits the anharmonic vibration of the crystal and further reduces the dielectric loss. At a sintering temperature of 1340 ℃, MgNb_2-_x(Ti_0.5W_0.5)_xO₆ (x=0.03) ceramics have excellent terahertz dielectric properties, with a dielectric constant (ε_r) of 19.32, a dielectric loss of 0.003 (@0.30 THz), and an absorption coefficient of 1.64 cm^-1 (@0.30 THz). The MgNb_2-_x(Ti_0.5W_0.5)_xO₆ (x=0.03) ceramics prepared in this study have a good application prospect in terahertz devices.

Key words: MgNb₂O₆ ceramic, crystal structure, complex chemical bond theory, internal strain, terahertz dielectric property

CLC Number:

O484

HUANG Zipeng, JIA Wenxiao, LI Lingxia. Crystal Structure and Terahertz Dielectric Properties of (Ti_0.5W_0.5)⁵⁺ Doped MgNb₂O₆ Ceramics[J]. Journal of Inorganic Materials, 2025, 40(6): 647-655.

Figures/Tables 10

Fig. 1 XRD analyses of MgNb2-x(Ti0.5W0.5)xO6 (x=0-0.03) ceramics (a) XRD patterns; (b) Cell parameters obtained by XRD refinement

Table 1 Reliability factor of XRD refinement results of MgNb2-x(Ti0.5W0.5)xO6 (x=0-0.03) ceramics

Parameter	x=0	x=0.01	x=0.02	x=0.03
R_wp/%	10.36	13.56	7.95	6.32
R_p/%	6.52	8.56	5.56	4.33

Fig. 2 (a) XRD refinement result and (b) crystal structure of MgNb2O6 ceramic

Fig. 3 Surface morphologies of MgNb2-x(Ti0.5W0.5)xO6 (x=0-0.03) ceramics sintered at 1340 ℃ (a) x=0; (b) x=0.01; (c) x=0.02; (d) x=0.03; Insets: particle size distribution

Table 2 Bond lengths (Å) in MgNb2-x(Ti0.5W0.5)xO6 (x=0-0.03) ceramics obtained from XRD refinement

Bond		x=0.01	x=0.02
Mg–O1$\times $2	2.0012	1.9033	2.0632	2.0821
Mg–O2(1)$\times $2	1.9892	2.0423	2.0032	2.0262
Mg–O2(2)$\times $2	2.0122	2.4343	2.0792	2.0631
Nb–O1(1)$\times $1	2.0223	2.1123	2.0642	2.0322
Nb–O1(2)$\times $1	2.1072	2.1612	2.0092	2.0082
Nb–O2$\times $1	1.9621	1.8313	1.8341	1.8441
Nb–O3(1)$\times $1	2.1461	1.9962	2.1121	2.1431
Nb–O3(2)$\times $1	2.0542	2.1362	2.1362	2.1191
Nb–O3(3)$\times $1	2.0662	2.1723	2.0152	2.0002

Fig. 4 Chemical bond characteristics of Mg-O and Nb-O bonds in MgNb2-x(Ti0.5W0.5)xO6 (x=0-0.03) ceramics (a) Average bond ionicity; (b) Average covalency; (c) Total lattice energy; (d) Total bond energy

Fig. 5 (a) Terahertz dielectric constants and (b) densities of MgNb2-x(Ti0.5W0.5)xO6 (x=0-0.03) ceramics

Fig. 6 (a) Terahertz dielectric loss and (b) absorption coefficient of MgNb2-x(Ti0.5W0.5)xO6 (x=0-0.03) ceramics

Table 3 B position chemical bond valences (Sij(B-O)) and global instability indexes (GII) of MgNb2-x(Ti0.5W0.5)xO6 (x=0-0.03) ceramics

Parameter	x=0	x=0.01	x=0.02	x=0.03
S_ij(B-O)	4.0657	4.1612	4.5383	4.5777
GII	0.7896	0.6069	0.3914	0.3458

Table 4 Atomic packing densities of MgNb2-x(Ti0.5W0.5)xO6 (x=0-0.03) ceramics

Parameter	x=0	x=0.01	x=0.02	x=0.03
Atomic packing density/%	71.25	71.33	71.46	71.50

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Crystal Structure and Terahertz Dielectric Properties of (Ti_0.5W_0.5)⁵⁺ Doped MgNb₂O₆ Ceramics

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