Crystal structure,bond energy,Raman spectra,and microwave dielectric properties of Ti-doped Li3Mg2NbO6 ceramics

Crystal structure exerts dominant influence on the microwave dielectric performance enabling satisfying the demands for 5G communication system. In this study, the Ti-doped Li₃Mg₂Nb_1-xTi_xO_6-x/2 (x = 0.0-0.1) ceramics were prepared by the solid-state reaction procedure. Crystal structure refinement and microstructure analysis indicate pure phase with orthorhombic structure and homogeneous microstructure with grain size (~14 μm). The relative permittivity was affected by the relative density, cell volume, and polarizability. The Q × f value was dominated by the Nb-O bond energy and grain size. The τ_f value was correlated with the NbO₆ octahedral distortion and Nb-O bond valence. Particularly, the composition (x = 0.04) exhibited remarkable microwave dielectric performance: ε_r = 15.88, Q × f = 131 000 GHz and τ_f = −26.8 ppm/°C, providing a promising candidate for millimeter-wave applications.     

Mg3B2O6 microwave dielectric ceramics fabricated by combining cold sintering with post-annealing process

It is difficult to get pure-phase Mg₃B₂O₆ (abbreviated as MBO) ceramics by the traditional high-temperature solid-state reaction method. In this paper, pure-phase MBO ceramics were successfully densified and obtained by combining the cold sintering and post-annealing process. The relative density of MBO ceramics was ∼80% cold sintered at 150°C/90 min/800 MPa, which was further improved to ∼91% by post-annealing at 900°C, 400°C lower than that of the traditional high-temperature sintering process (∼1300°C). X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Raman results demonstrated that the secondary phase of MgO was effectively eliminated, and dense microstructure was observed by the cold-sintering process plus post-annealing treatment. Finally, the microwave dielectric properties of MBO were evaluated with ε_r: 5.15–6.37, Q×f: 5942–16 686 GHz, τ_f: −48.45–69.72 ppm/°C.     

Correlation between crystal structure and modified microwave dielectric characteristics of Cu2+ substituted Li3Mg2NbO6 ceramics

Structural characteristics exert significant influences on microwave dielectric properties, and ion substitution is widely adopted to modify material performances by adjusting the crystal structure. In this work, low loss Li₃Mg_2-xCu_xNbO₆ (x?=?0–0.04) ceramics were prepared by Cu²⁺ substitution. The impacts of Cu²⁺ substitution for Mg²⁺ sites on the microwave dielectric characteristics and crystal structure were discussed in detail. Rietveld refinement results implied that a single Li₃Mg₂NbO₆ phase was formed. Additionally, a dense and homogeneous microstructure with grain sizes of 7–9?μm could be achieved, and moderate Cu²⁺ substitution could significantly promote the grain growth. The correlation between microwave dielectric characteristics and crystal structure was discussed by calculating some structural parameters. The ε_r was determined by the polarizability. The Q?×?f was influenced by the packing fraction. The τ_f value was dependent on the NbO₆ octahedron distortion, and the τ_f value could be adjusted to near zero for x?=?0.02. Typically, the Li₃Mg_2-xCu_xNbO₆ (x?=?0.02) composition exhibited remarkable microwave dielectric performances: ε_r?=?15.75, Q?×?f?=?92,134?GHz (9.86?GHz) and τ_f?=??2?ppm/°C, making it a promising candidate for temperature-stable millimeter-wave applications.     

Low‐temperature sintering and thermal stability of Li2GeO3‐based microwave dielectric ceramics with low permittivity

A low‐permittivity dielectric ceramic Li₂GeO₃ was prepared by the solid‐state reaction route. Single‐phase Li₂GeO₃ crystallized in an orthorhombic structure. Dense ceramics with high relative density and homogeneous microstructure were obtained as sintered at 1000‐1100°C. The optimum microwave dielectric properties were achieved in the sample sintered at 1080°C with a high relative density ~ 96%, a relative permittivity ε_r ~ 6.36, a quality factor Q × f ~ 29 000 GHz (at 14.5 GHz), and a temperature coefficient of resonance frequency τ_f ~ ?72 ppm/^°C. The sintering temperature of Li₂GeO₃ was successfully lowered via the appropriate addition of B₂O₃. Only 2 wt.% B₂O₃ addition contributed to a 21.2% decrease in sintering temperature to 850°C without deteriorating the dielectric properties. The temperature dependence of the resonance frequency was successfully suppressed by the addition of TiO₂ to form Li₂TiO₃ with a positive τ_f value. These results demonstrate potential applications of Li₂GeO₃ in low‐temperature cofiring ceramics technology.     

Effects of W6+ substitution on crystal structure and microwave dielectric properties of Li3Mg2NbO6 ceramics

Li₃Mg₂(Nb_1-xW_x)O_6+x/2 (0 ≤ x ≤ 0.08) ceramics were synthesized by the solid-state reaction route. The effects of W⁶⁺ substitution on the phase composition, microstructure and microwave dielectric properties of Li₃Mg₂NbO₆ ceramics were investigated systematically. The XRD results showed that all the samples formed a pure solid solution in the whole doping range. The SEM iamges and relative density revealed the dense structure of Li₃Mg₂(Nb_1-xW_x)O_6+x/2 ceramics. The relationship between the crystal structure and dielectric properties of Li₃Mg₂(Nb_1-xW_x)O_6+x/2 ceramics was researched through polarizability, average bond valence, and bond energy. The substitution of W⁶⁺ for Nb⁵⁺ in Li₃Mg₂(Nb_1-xW_x)O_6+x/2 ceramics significantly promoted the Q × f values. In addition, the increase of W⁶⁺ content improved the thermal stability of the Li₃Mg₂(Nb_1-xW_x)O_6+x/2 ceramics. The Li₃Mg₂(Nb_0.94W_0.06)O_6.03 ceramics sintered at 1175 °C for 6h possessed excellent properties: ε_r ~ 15.82, Q × f ~ 124,187 GHz, τ_f ~ −18.28 ppm/°C.     

Ba缺位和烧结工艺对Ba1-xZn1/3Nb2/3O3陶瓷离子有序度和微波介电性能的影响

利用常规固相法制备了Ba1-xZn1/3Nb2/303(x=O～0.02)陶瓷,研究了Ba缺位对Ba1-xZn1/3Nb2/3O3陶瓷的相成分、B位离子长程有序度(LRO)和微波介电性能的影响规律.X射线衍射(XRD)结果显示,适量的Ba缺位可以提高材料的阳离子有序度,x=0.01时陶瓷具有最大的阳离子有序度;Ba缺位...     

Structure,chemical bond and microwave dielectric characteristics of novel Li3Mg4NbO8 ceramics

A novel Li₃Mg₄NbO₈ compound was fabricated through the process of solid-state reaction. The crystal structure, sinterability and microwave dielectric properties of the Li₃Mg₄NbO₈ ceramics were investigated. XRD refinement and Raman spectra results ascertained that the Li₃Mg₄NbO₈ compound crystallized into an orthorhombic Li₃Mg₂NbO₆-like structure with space group Fddd. The ε_r value was strongly impacted by the relative density and average ionic polarization. The Q × f value was mainly affected by the relative density and average grain size. The Li₃Mg₄NbO₈ ceramics sintered at 1150 ℃ showed outstanding microwave dielectric performance: ε_r = 13.8 ± 0.14, Q × f = 103 400 ± 3500 GHz (at 9.6 GHz), τ_f = −36.0 ± 1 ppm/℃. Additionally, the bond characteristics were calculated for a better understanding of the structure-property correlation for Li₃Mg₄NbO₈ ceramics.     

Investigation of phase composition and microwave dielectric properties of MgO‐Ta2O5 ceramics with ultrahigh Qf value

Four MgO‐Ta₂O₅ ceramics with the MgO/Ta₂O₅ mole ratio x = 1, 2, 3, and 4 were prepared by traditional solid‐state reaction method, and the influence of x on the phase composition, microstructure, and dielectric properties (the dielectric constant ε_r, the temperature coefficient of resonant frequency τ_f and the quality factor Qf) of the materials was investigated using XRD, SEM, etc. The results indicated that the ceramics were composed of two crystalline phases MgTa₂O₆ and Mg₄Ta₂O₉ in the composition range studied, and that the dielectric properties ln ε, 1/Qf, and τ_f changed proportionally to the fraction of main crystal phases, which meet perfectly with the mixing model proposed in this study. It is obvious that the proportion of the two crystal phases could be precisely controlled by x, and thereby, the dielectric properties can be conveniently and precisely tailored. Our research provided a new microwave dielectric ceramic with the composition of 2MgO‐Ta₂O₅, which has an ultrahigh Qf value (211 000 GHz), low dielectric constant ε_r (19.9), and near zero temperature coefficient of resonant frequency τ_f (8 ppm/°C).     

Cold sintering and microwave dielectric properties of dense HBO2-II ceramics

HBO₂-II ceramics were prepared by cold sintering with 10wt% dehydrated ethanol as the transient liquid phase. When the processing temperature is 30°C, the relative density of the mechanically robust HBO₂-II ceramics increases from 77.5% to 84.5% with increasing the uniaxial pressure from 200 to 500 MPa. It changes less than 0.2% for higher pressure up to 700 MPa. Under a constant uniaxial pressure of 500 MPa, the relative density further increases to 94.7% for the processing temperature of 120°C. HBO₂-I is observed as the secondary phase when the processing temperature is 150°C. In comparison, the compacts prepared in the absence of ethanol are fragile, and the relative densities are 78.5%-84.5% for the processing temperatures of 30-120°C and uniaxial pressure of 500 MPa. It is indicated that ethanol promotes the densification significantly through the dissolution-precipitation mechanism. The permittivity increases with increasing the processing temperature, while the Qf value decreases. The optimal properties with the relative density of 94.7%, ε_r = 4.21, Qf = 47 500 GHz, and τ_f = −70.0 ppm/°C were obtained in the single-phase HBO₂-II ceramics cold sintered at 120°C under 500 MPa for 10 minutes. The relative density and Qf value are significantly higher than those of the HBO₂-II ceramic prepared by sintering the H₃BO₃ compact at 180°C for 2 hours (70.3% and 32 700 GHz, respectively). The results indicate that the nonaqueous solvent can also be used as the transient liquid phase for cold sintering, so that more materials that are unstable or insoluble in water can be densified by this method.     

Synthesis,crystal structure and low loss of Li3Mg2NbO6 ceramics by reaction sintering process

An investigation into an effective and simple process for the production of a low-cost material with high production efficiency has resulted in a significant impact on commercial production. In the present work, we synthesized the low loss Li₃Mg₂NbO₆ ceramic using an effective and simple reaction sintering process. A single orthorhombic phase was corroborated by XRD and Rietveld refinement. The packing fraction and Nb-O bond valence were determined according to the Rietveld refinement results to explore the relationship between the structure and microwave dielectric performance. The Raman analysis indicated that the shift of the band near 772 cm^-1 assigned to the Mg-O bond vibration was consistent with the diversification of the cell volume. Furthermore, dense and homogeneous microstructures with large grain sizes (∼130 μm) were obtained when sintered at 1350 °C. The relative density exerted an influence on the dielectric constant, while the packing fraction and grain size influenced the Q × f value of the Li₃Mg₂NbO₆ ceramics. Moreover, the Nb-O bond valence dominated the τ_f value of the Li₃Mg₂NbO₆ ceramics. Excellent microwave dielectric characteristics for the samples sintered at 1350 °C: ε_r = 14.5, Q × f = 116,000 (9.76 GHz) GHz and τ_f = −24.5 ppm/°C were achieved by the reaction sintering process, exhibiting a potential for industrial production.     

Influence of Cr3+ substitution for Mg2+ on the crystal structure and microwave dielectric properties of CaMg1-xCr2x/3Si2O6 ceramics

The CaMg_1-xCr_2x/3Si₂O₆ (0?≤?x?≤?0.1) microwave dielectric ceramics were synthesized via conventional solid state reaction. In this study, the effects of Cr³⁺ substituting for Mg²⁺ on morphology, crystal structure and microwave dielectric properties of CaMg_1-xCr_2x/3Si₂O₆ ceramics were explored. XRD diffraction patterns exhibited that the CaMg_1-xCr_2x/3Si₂O₆ ceramics possessed the pure phase of CaMgSi₂O₆ when x?≤?0.06 and a small amount of secondary phase Ca₃Cr₂(SiO₄)₃ for 0.08?≤?x?≤?0.1. SEM micrographs revealed that the substitution of Mg²⁺ with Cr³⁺ could decrease the grain size. The apparent density was affected by the concentration of Mg vacancies. The correlation between crystal structure and microwave dielectric properties was investigated through the Rietveld refinement and Raman analysis. The microwave dielectric properties were mainly dependent on relative density, ionic polarizabilities, internal strain ?, disordered structure and MgO₆ octahedron distortions. Finally, CaMg_1-xCr_2x/3Si₂O₆ (x?=?0.02) ceramics sintered at 1270?°C for 3?h exhibited excellent microwave dielectric properties of ε_r?=?8.06, Q?×?f?=?89054?GHz, τ_f?=??44.92182?ppm/ºC.     

Parallel preparation and properties investigation on Li2O-Nb2O5-TiO2 microwave dielectric ceramics

A parallel preparation method was developed using dry powders as starting materials to synthesize multi-compositional microwave dielectric ceramics. The Li₂O-Nb₂O₅-TiO₂ ternary system was investigated as a model material. The validity of the parallel ceramic preparation process was confirmed by synthesizing a group of LiNb_0.6Ti_0.5O₃ ceramics in parallel, which showed the same crystalline structure and close dielectric properties. The ceramic libraries with M-phase-rich samples and Li₂TiO₃-rich samples were prepared using the parallel process, and the microwave dielectric properties and crystal phases were investigated systematically. An excellent microwave ceramic with a composition of 0.55Li₂O-0.05Nb₂O₅-0.40TiO₂ was obtained, which has a dielectric constant of 18.4 and a high quality value (Q × f) of 79000 GHz. This parallel process can be applied extensively to explore a variety of bulk ceramic libraries for discovering new functional materials with high performances.     

Correlation between structural characteristics and microwave dielectric properties of walstromite BaCa2M3O9 (M = Si,Ge) ceramics

Novel BaCa₂M₃O₉ (M = Si, Ge) microwave dielectric ceramics were prepared via solid-state reaction with sintering at 1125°C–1275°C for 5 h. Single-phase BaCa₂M₃O₉ (M = Si, Ge) ceramics were obtained according to stoichiometry. The single-phase BaCa₂Ge₃O₉ ceramic was confirmed through Rietveld refinement and high-resolution transmission electron microscopy/selected area electron diffraction and synthesized for the first time. The BaCa₂M₃O₉ (M = Si, Ge) exhibited a triclinic structure with a P$\overline{1}$ space group and good microwave dielectric properties. The ε_r, Q × f, and τ_f values of BaCa₂M₃O₉ (M = Si, Ge) ceramics are mostly dominated by the relative density, ionic polarizability, relative covalence, and bond energy of M–O bond, respectively. A high Q × f value (61 800 GHz at 16.3 GHz) was obtained in BaCa₂Ge₃O₉ ceramic due to its high r_c (Ge–O) and low intrinsic dielectric loss. The BaCa₂Si₃O₉ ceramic exhibited small |τ_f| value (‒36.4 ppm/°C) due to its large E_Si-O. Excellent microwave dielectric properties (ε_r = 8.31, Q × f = 61 800 GHz, and τ_f = ‒58.7 ppm/°C) were obtained for the BaCa₂Ge₃O₉ ceramic.     

Optimized crystal structure and microwave dielectric properties of BaZnSi3O8-based ceramics

In this study, we synthesized BaZnSi₃O₈-based compounds with monoclinic structures (P21/a) using a solid-state method. The crystal structure, phase composition, and microwave dielectric properties of BaZnSi₃O₈-based ceramics were systematically investigated systematically. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images proved that the maximum solubility of BaZn_1-xMg_xSi₃O₈ ranged between 0.3 and 0.4. Rietveld refinement and Phillips–Van Vechten–Levine complex chemical bond theory were used to illustrate the relationship between the microwave dielectric performance and lattice parameters. To further improve the properties, we substituted Ba²⁺ with Sr²⁺ in BaZn_0.8Mg_0.2Si₃O₈. Ba_1-ySr_yZn_0.8Mg_0.2Si₃O₈ remained in a single-phase as y increased from 0 to 1.0. We achieved thermal stability of the resonance frequency of the BaZnSi₃O₈-based ceramics by adjusting TiO₂ to form composite ceramics. After sintering at 1020°C for 5 h, excellent microwave dielectric properties with ε_r = 7.44, Q×f = 57,400 GHz, and τ_f = − 0.2 ppm/°C were realized in the SrZn_0.8Mg_0.2Si₃O₈+8 wt %TiO₂ system.     

Phase formation and microwave dielectric properties of BiMVO5 (M = Ca,Mg) ceramics potential for low temperature co-fired ceramics application

Two low-firing BiMVO₅ (M = Ca, Mg) ceramics were prepared in the sintering temperature range of 760-850°C. Their differences in phase formation, sintering behavior, and dielectric performances were investigated. BiCaVO₅ formed a single phase with an orthorhombic structure, while BiMgVO₅ crystallized in a monoclinic structure that needs longer dwelling time to obtain single phase. The optimized microwave dielectric properties were obtained with ε_r = 15.70, Q × f = 55 000 GHz (at 10.6 GHz), and τ_f = −71 ppm/°C for BiCaVO₅, ε_r = 18.55, Q × f = 86 860 GHz (at 9.63 GHz), and τ_f = −65 ppm/°C for BiMgVO₅. In addition, the large negative τ_f values of BiMVO₅ (M = Ca, Mg) ceramics were successfully adjusted by forming composite ceramics with CaTiO₃ and near-zero τ_f values of +2 ppm/°C and −3 ppm/°C were obtained in 0.92BiCaVO₅-0.08CaTiO3 and 0.94BiMgVO₅-0.06CaTiO₃, respectively. Both ceramics exhibited good chemical compatibility with Ag electrode. The results demonstrate BiMVO₅ (M = Ca, Mg) ceramics to be attractive candidates in LTCC technology.     

The relationship between crystal structure and modified microwave dielectric properties of Ca3SnSi2-xGexO9 ceramics

Ca₃SnSi_2-xGe_xO₉ (0 ≤ x ≤ 0.8) and (1–y) Ca₃SnSi_1.6Ge_0.4O₉ – y CaSnSiO₅ – 2 wt% LiF (y = 0.4 and 0.5) microwave dielectric ceramics were prepared by traditional solid-state reaction through sintering at 1250°C–1425°C for 5 h and at 875°C for 2 h, respectively. Ge⁴⁺ replaced Si⁴⁺, and Ca₃SnSi_2-xGe_xO₉ (0 ≤ x ≤ 0.4) solid solutions were obtained. At 0.1 ≤ x ≤ 0.4, the Ge⁴⁺ substitution for Si⁴⁺ decreased the sintering temperature of Ca₃SnSi_2-xGe_xO₉ from 1425 to 1300°C, the SnO₆ octahedral distortions, and the average CaO₇ decahedral distortions, which affected the τ_f value. The large average decahedral distortions corresponded with nearer-zero τ_f values at Ca₃SnSi_2-xGe_xO₉ (0.1 ≤ x ≤ 0.4) ceramics. The τ_f value and sintering temperature of Ca₃SnSi_2-xGe_xO₉ (x = 0.4) ceramic were adjusted to near-zero by CaSnSiO₅ and decreased to 875°C upon the addition of 2 wt% LiF. The (1 – y) Ca₃SnSi_1.6Ge_0.4O₉ – y CaSnSiO₅ – 2 wt% LiF (y = 0.5) ceramic sintered at 875°C for 2 h exhibited good microwave dielectric properties: ε_r = 10.3, Q × f = 14 300 GHz (at 12.2 GHz), and τ_f = ‒5.8 ppm/°C.     

Effect of Li nonstoichiometry and TiO2 addition on the microwave dielectric properties of Li3PO4 ceramics

Li₃PO₄ ceramic is a promising microwave ceramic material with low dielectric constant. The effect of Li nonstoichiometry on phase compositions, microstructures, and microwave dielectric characteristics of Li₃PO₄ ceramics, on the other hand, has been examined infrequently. Therefore, in the first part of this study, the stoichiometry and Li nonstoichiometry compositions based on Li_3+xPO₄(x = 0, 0.03, 0.06, 0.09, 0.12 and 0.15) were prepared by conventional solid-phase method. The results show that a few nonstoichiometric lithium ions enter the lattice of Li_3+xPO₄. Compared with the chemical content of Li₃PO₄, the sintering characteristics, relative dielectric constants and quality factors of Li_3+xPO₄ ceramics can be improved by slightly excessive Li ions, while the properties of Li₃PO₄ ceramics can be deteriorated by excessive Li ions. Li_3.12PO₄ ceramics sintered at 975 °C for 2 h have good dielectric properties (ε_r = 5.89, Q×f = 44,000 GHz, τ_f = ?206 ppm/^°C). In order to improve its large negative temperature coefficient of resonant frequency, in the following study, rutile nano TiO₂ particles were added as τ_f compensator. Adding TiO₂ powders not only effectively improve the temperature stabilities of the multiphase ceramics, but also make the grain growth more uniform. With the increase of TiO₂ content from 0.40 to 0.60, τ_f increases from ?73.5 ppm/^°C to +42.3 ppm/^°C. The best dielectric property of 0.45Li_3.12PO₄-0.55TiO₂ composite ceramic is ε_r = 13.29, Q×f = 40,700 GHz, τ_f = +8.8 ppm/^°C.     

Crystal structure and microwave dielectric properties of NaPb2B2V3O12(B=Mg,Zn) ceramics

Two low temperature sintered NaPb₂B₂V₃O₁₂ (B?=?Mg, Zn) ceramics with garnet structure were synthesized through conventional solid state reaction route and their crystal structure and microwave dielectric properties were investigated for the first time. Rietveld refinements of XRD patterns show both the compounds belong to cubic symmetry with space group Ia-3d. Observed number of Raman bands and group theoretical predictions also confirm cubic symmetry with space group Ia-3d for both NPMVO and NPZVO. At the optimum sintering temperature of 725?°C NPMVO has a relative permittivity of 20.6?±?0.2, unloaded quality factor (Q_uxf) of 22,800?±?1500?GHz (f?=?7.7?GHz) and temperature coefficient of resonant frequency +25.1?±?1?ppm/°C while NPZVO has relative permittivity of 22.4?±?0.2, Q_uxf of 7900?±?1500?GHz (f?=?7.4?GHz) and near zero temperature coefficient of resonant frequency of -6?±?1?ppm/°C at 650?°C. The relative permittivity of the compounds is inversely related to the corresponding Raman shifts.     

Ba(Mg1/3Nb2/3)O3-Mg4Nb2O9复相陶瓷微波介电性能研究

采用传统固相法制备了(1?x)Ba(Mg1/3Nb2/3)O3?xMg4Nb2O9 [(1?x)BMN?xM4N2,x = 0.003 ~ 0.125] 微波介质陶瓷,研究了相结构、烧结性能与介电性能随 x 的变化规律。结果表明： BMN 与 M4N2 可以两相共存,且二者间存在有限固溶,BMN 的烧结温度及高温稳定性有所降 低。随着 x 的增大,介电常数 εr和谐振频率温度系数 τf逐渐减小,Q × f 值的变化易受到 BMN 有序参数 S 的影响,高度 1:2 有序的 x = 0.026 陶瓷获得了最大 Q × f 值 125000 GHz。综合来看, 在 1320°C 下保温 4 h 烧结的 x = 0.125 样品表现出最佳的微波介电性能：εr = 26.6,Q × f = 111000 GHz,τf = 5 ppm/ºC。     

Crystal structure,phase transition,vibrational spectra,and microwave dielectric characteristics of Ta5+ ionic substituted Co0.5Ti0.5NbO4 ceramics

In the present research, structural representation, phase transition, and dielectric characteristics of Ta⁵⁺ ionic substituted Co_0.5Ti_0.5(Nb_1-xTa_x)O₄ (x = 0–1) ceramics were thoroughly investigated. Combined with the changes of diffraction peaks in the X-ray diffraction spectra, such as (002) and (101) crystalline planes near 20°, and the evolutionary trend of the strongest peak in the Raman spectra, a phase transition from rutile to trirutile structure at x = 0.6 was confirmed, suggesting the emergence of structural evolution. Thus, the structural evolution showed a significant impact on the dielectric characteristics, as evidenced by the weakening of the dielectric polarizability with the increasing amount of Ta⁵⁺ ion, which led to a reduction in the dielectric constant; the dielectric loss is also closely related to the packing fraction (PF) arising from the structural changes. Additionally, infrared and THz time-domain spectroscopy revealed that the dielectric losses in the microwave band were originated from the oscillatory absorption of structural phonons and supported that the effects of structural evolution on the intrinsic dielectric properties due to the introduction of Ta⁵⁺ ion.