The effect of sintering temperature and time on microwave properties of Sm(Zn1/2Ti1/2)O3 ceramics for resonators

The microwave dielectric properties of Sm(Zn_1/2Ti_1/2)O₃ ceramics have been investigated. Sm(Zn_1/2Ti_1/2)O₃ ceramics were prepared by conventional solid-state route with various sintering temperatures and times. The prepared Sm(Zn_1/2Ti_1/2)O₃ exhibited a mixture of Zn and Ti showing 1:1 order in the B-site. Higher sintered density of 7.01 g/cm³ can be produced at 1310 °C for 2 h. The dielectric constant values (ɛ_r) of 22–31 and the Q × f values of 4700–37,000 (at 8 GHz) can be obtained when the sintering temperatures are in the range of 1250–1370 °C for 2 h. The temperature coefficient of resonant frequency τ_f was a function of sintering temperature. The ɛ_r value of 31, Q  ×  f value of 37,000 (at 8 GHz) and τ_f value of −19 ppm/°C were obtained for Sm(Zn_1/2Ti_1/2)O₃ ceramics sintered at 1310 °C for 2 h. For applications of high selective microwave ceramic resonator, filter and antenna, Sm(Zn_1/2Ti_1/2)O₃ is proposed as a suitable material candidate.     

Microwave dielectric properties of Bi-substituted La(Mg1/2Ti1/2)O3

The system La(Mg_1/2Ti_1/2)O₃–Bi(Mg_1/2Ti_1/2)O₃ (LMT–BMT) was investigated in respect to formation of perovskite solid solutions based on lanthanum magnesium titanate. Single-phase perovskite (1 − x)LMT–xBMT ceramics (0 ≤ x ≤ 0.3) were prepared and their crystal structure and dielectric properties were studied. It has been found that within the solubility range the crystal structure of Bi-substituted LMT remains monoclinic, P2₁/n. Unit cell volume was evaluated to be almost independent on x, varying within the experimental error. Relative permittivity of the ceramics increases by almost a factor of 3 in the range 0 ≤ x ≤ 0.3 and its value is 40–45 at the compositional region where temperature coefficient of the resonant frequency passes a zero-value. Compositional and temperature variations of the dielectric parameters for LMT–BMT estimated at different frequency ranges are considered in comparison with those observed in other Bi-substituted ceramics based on LMT.     

Microwave dielectric properties and microstructures of Nd(Mg0.5Sn0.5−xTix)O3 ceramics

This study elucidates the microwave dielectric properties and microstructures of Nd(Mg_0.5Sn_0.5?xTi_x)O₃ ceramics with a view to their potential for microwave devices. The Nd(Mg_0.5Sn_0.5?xTi_x)O₃ ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the Nd(Mg_0.5Sn_0.4Ti_0.1)O₃ ceramics revealed no significant variation of phase with sintering temperatures. A dielectric constant (?_r) of 21.1, a quality factor (Q × f) of 50,000 GHz, and a temperature coefficient of resonant frequency (τ_f) of ?60 ppm/°C were obtained for Nd(Mg_0.5Sn_0.4Ti_0.1)O₃ ceramics that were sintered at 1550 °C for 4 h.     

Effect of nonstoichiometry on the structure and microwave dielectric properties of Ba(Co1/3Nb2/3)O3 ceramics

The effect of B-site cation deficiency on the structure and microwave dielectric properties of Ba(Co_1/3Nb_2/3)O₃ (BCN) was investigated. Stoichiometric and co-deficient compositions based on Ba(Co_1/3−xNb_2/3)O₃ [x = 0.0, 0.01, 0.02, 0.03 and 0.04] were prepared using the conventional mixed oxide route. Small amounts of V₂O₅ (0.1 wt%) were added to promote densification. The dielectric loss is very sensitive to the composition; it was found that co-deficiency degraded the microwave dielectric properties. The stoichiometric formulation (x = 0) exhibited the best microwave properties. The improvements in the microwave dielectric properties were achieved by increasing the degree of 1:2 cation ordering. The highly ordered, stoichiometric BCN ceramics showed a relative permittivity (ɛ_r) of 32, quality factor (Q × f) of 66,500 GHz and a negative temperature coefficient of resonant frequency (τ_f) of −10 ppm/°C at 4 GHz.     

Low temperature sintering of the Ba2Ti9O20 ceramics using B2O3/CuO and BaCu(B2O5) additives

The effects of B₂O₃/CuO and BaCu(B₂O₅) additives on the sintering temperature and microwave dielectric properties of Ba₂Ti₉O₂₀ ceramics were investigated. The B₂O₃ added Ba₂Ti₉O₂₀ ceramics were not able to be sintered below 1000 °C. However, when both CuO and B₂O₃ were added, they were sintered below 900 °C and had the good microwave dielectric properties. It was suggested that a liquid phase with the composition of BaCu(B₂O₅) was formed during the sintering and assisted the densification of the Ba₂Ti₉O₂₀ ceramics at low temperature. BaCu(B₂O₅) powders were produced and used to reduce the sintering temperature of the Ba₂Ti₉O₂₀ ceramics. Good microwave dielectric properties of Qxf = 16,000 GHz, ɛ_r = 36.0 and τ_f = 9.11 ppm/°C were obtained for the Ba₂Ti₉O₂₀ ceramics containing 10.0 mol% BaCu(B₂O₅) sintered at 875 °C for 2 h.     

Effect of non-stoichiometry on the densification,phase purity,microstructure, crystal structure,and dielectric loss of Ba(Co1/3Nb2/3)O3 ceramics

The structural, vibrational, densification, and microwave properties of Ba(Co_1/3Nb_2/3)O₃ ceramics with small compositional variations along several tie lines in the ternary BaOCoONb₂O₅ diagram were studied. The results showed that very small deviation from stoichiometric Ba(Co_1/3Nb_2/3)O₃ composition has profound effect on Q × f, degree of ordering, densification, and phase assemblage. The 0.94 Ba(Co_1/3Nb_2/3)O₃–0.06 Ba₅Nb₄O₁₅ ceramic has the highest Q × f value (71 THz) – a value two times larger than that of stoichiometric Ba(Co_1/3Nb_2/3)O₃ (36 THz). Transformation from the (partial) disordered distribution of Co and Nb cations to 1:2 ordered arrangement in the octahedral sites was found to increase the Q factor of the high density and single phase ceramics. It was also observed that formation of very small amount of Ba₉CoNb₁₄O₄₅ second phase degraded Q × f value severely for the dense and highly ordered Nb-rich and Ba-deficient ceramics.     

Structure and properties of La(Zn1/2Ti1/2)O3

(La,Nd)(Zn,Mg)_0.5Ti_0.5O₃ compounds are of great interest for microwave dielectric applications, although the structure of some of these complex perovskites is still uncertain. The perovskite tolerance factors in this family of compounds range from 0.916 to 0.952, suggesting a very high degree of tilting in the oxygen octahedra for compositions throughout the system. The effects of this tilting in La(Zn_0.5Ti_0.5)O₃, for example, have been observed in this study by transmission electron microscopy in the form of 1/2{3 1 1}_c and 1/2{1 3 1} α superlattice reflections and 1/2(2 3 1)_c γ reflections corresponding to anti-phase and in-phase tilting, respectively. Systematic La⁺³ displacement was also detected by the appearance of {h + 1/2, k, l}_c (β) reflections. Reflections of the type 1/2{1 1 1}_c in neutron diffraction patterns indicate 1:1 cation ordering on the B-site. Electrical tests show no piezoelectricity in La(Zn_0.5Ti_0.5)O₃, indicating a centrosymmetric point group. Rietveld refinements of neutron diffraction patterns indicate that the space group is P2₁/n, with lattice constants a = 7.8943 Å, b = 5.5959 Å, c = 5.5805 Å, and β = 90.0291°.     

Effects of Li2CO3 and Sm2O3 additives on low-temperature sintering and piezoelectric properties of PZN-PZT ceramics

To assist the development of applications for multilayer piezoelectric devices, the low-temperature sintering piezoelectric ceramics of 0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.49Ti_0.51)O₃ with Li₂CO₃ and Sm₂O₃ additives were fabricated by a conventional solid-state reaction, and their structural and piezoelectric properties were studied. With the addition of Li₂CO₃, the minimum sintering temperature of 0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.49Ti_0.51)O₃ piezoelectric ceramics was reduced from 1125 °C to 950 °C through the formation of a liquid phase and its piezoelectric properties showed almost no degradation. When the sintering temperature was below 950 °C, however, the piezoelectric properties degraded obviously. The additional Sm₂O₃ resulted in a significant improvement in the piezoelectric properties of 0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.49Ti_0.51)O₃ ceramic with added Li₂CO₃. When sintered at 900 °C, the optimized properties of the 0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.49Ti_0.51)O₃ piezoelectric ceramic with 0.3 wt% Li₂CO₃ and 0.3 wt% Sm₂O₃ were obtained as d₃₃ = 483 pC/N, k₃₁ = 0.376, Q_m = 73, ɛ_r = 2524, tan δ = 0.0178.     

Dielectric behaviors of Nb2O5–Co2O3 doped BaTiO3–Bi(Mg1/2Ti1/2)O3 ceramics

Nb₂O₅ and Nb–Co doped 0.85BaTiO₃–0.15Bi(Mg_1/2Ti_1/2)O₃ (0.85BT–0.15BMT) ceramics were investigated. From XRD patterns, undesired phase was observed when the (Nb₂O₅/Nb-Co) doping levels exceed 3 wt.%/2 wt.%, giving rise to the deteriorate dielectric constant. The 0.85BT–0.15BMT ceramics doped with 2 wt.%Nb₂O₅ was found to possess a moderate dielectric constant (? ～ 1000) and low dielectric loss (tan δ = 0.9%) at room temperature and 1 kHz, showing flat dielectric behavior over the temperature range from ?55 to 155 °C. It was found that the formation of core–shell structure in the BT based ceramics is controlled by the doping sequence of Nb- and Bi-oxides.     

Effect of B2O3 and CuO additives on the sintering temperature and microwave dielectric properties of Ba(Zn1/3Nb2/3)O3 ceramics

The B₂O₃ added Ba(Zn_1/3Nb_2/3)O₃ (BBZN) ceramic was sintered at 900 °C. BaB₄O₇, BaB₂O₄, and BaNb₂O₆ second phases were found in the BBZN ceramic. Since BaB₄O₇ and BaB₂O₄ second phases have an eutectic temperature around 900 °C, they might exist as the liquid phase during sintering at 900 °C and assist the densification of the BZN ceramics. Microwave dielectric properties of dielectric constant (ɛ_r) = 32, Q × f = 3500 GHz, and temperature coefficient of resonance frequency (τ_f) = 20 ppm/°C were obtained for the BZN with 5.0 mol% B₂O₃ sintered at 900 °C for 2 h. The BBZN ceramics were not sintered below 900 °C and the microwave dielectric properties of the BBZN ceramics sintered at 900 °C were very low. However, when CuO was added, BBZN ceramic was well sintered even at 875 °C. The liquid phase related to the BaCu(B₂O₅) second phase could be responsible for the decrease of sintering temperature. Good microwave dielectric properties of ɛ_r = 36, Q × f = 19,000 GHz and τ_f = 21 ppm/°C can be obtained for CuO doped BBZN ceramics sintered at 875 °C for 2 h.     

Broadband dielectric spectroscopy of PbMg1/3Nb2/3O3–PbSc1/2Nb1/2O3 ceramics

Broadband dielectric spectroscopy results of various ordered and disordered (1 ? x)Pb(Mg_1/3Nb_2/3)O₃–(x)Pb(Sc_1/2Nb_1/2)O₃ (PMN–PSN) ceramics are investigated in the temperature range from 80 K to 300 K and frequency range from 20 Hz to 2 THz. Dielectric dispersion is very broad and in the ferroelectrics case (x = 1, 0.95) consists of two parts: low-frequency part caused by ferroelectric domains and higher frequency part caused by soft mode. The relaxational soft mode exhibits pronounced softening close to phase transition temperature, as it is typical for order–disorder phase transitions. By substituting Sc³⁺ by Mg²⁺ in PMN–PSN ceramics relaxation slows down, and for relaxors (x = 0.2) the most probable relaxation frequency decreases on cooling according to Vogel–Fulcher law.     

Improved dielectric properties and grain boundary response of SrTiO3 doped Y2/3Cu3Ti4O12 ceramics fabricated by Sol-gel process for high-energy-density storage applications

A chemical solution processing method based on sol-gel chemistry (SG) was used to synthesize (1-x)Y_2/3Cu₃Ti₄O₁₂-xSrTiO₃ (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) ceramics successfully. The 0.85Y_2/3Cu₃Ti₄O₁₂-0.15SrTiO₃ ceramics sintered at 1050 °C for 20 h showed fine-grained microstructure and high dielectric constant (ε′ ≈ 1.7 × 10⁵) at 1 kHz. Furthermore, the 0.85Y_2/3Cu₃Ti₄O₁₂-0.15SrTiO₃ ceramics appeared distinct pseudo-relaxor behavior. Two electrical responses were observed in the combined modulus and impedance plots, indicating the presence of Maxwell-Wagner relaxation. Sr vacancies and additional oxygen vacancies had substantial contribution to the sintering behavior, an increase in grain growth, and relaxation behaviors in grain boundaries. The contributions of semiconducting grains with the nanodomain and insulating grain boundaries (corresponding to high-frequency and low-frequency electrical response, respectively) played important roles in the dielectric properties of (1-x)Y_2/3Cu₃Ti₄O₁₂-xSrTiO₃ ceramics. The occurrence of the polarization mechanism transition from the grain boundary response to the electrode one with temperature change was clearly evidenced in the low frequency range.     

Structure and dielectric properties of perovskite ceramics in the system Ba(Ni1/3Nb2/3)O3–Ba(Zn1/3Nb2/3)O3

Ceramics in the system Ba(Ni_1/3Nb_2/3)O₃–Ba(Zn_1/3Nb_2/3)O₃ (BNN–BZN) were prepared by the mixed oxide route. Powders were mixed and milled, calcined at 1100–1200 °C then pressed and sintered at temperatures in the range 1400–1500 °C for 4 h. Selected samples were annealed or slowly cooled after sintering. Most products were in excess of 96% theoretical density. X-ray diffraction confirmed that all specimens were ordered to some degree and could be indexed to hexagonal geometry. Microstructural analysis confirmed the presence of phases related to Ba₅Nb₄O₁₅ and Ba₈Zn₁Nb₆O₂₄ at the surfaces of the samples. The end members BNN and BZN exhibited good dielectric properties with quality factor (Qf) values in excess of 25,000 and 50,000 GHz, respectively, after rapid cooling at 240 °C h⁻¹. In contrast, mid-range compositions had poor Qf values, less than 10,000 GHz. However, after sintering at 1450 °C for 4 h and annealing at 1300 °C for 72 h, specimens of 0.35(Ba(Ni_1/3Nb_2/3)O₃)–0.65(Ba(Zn_1/3Nb_2/3)O₃) exhibit good dielectric properties: τ_f of +0.6 ppm °C⁻¹, relative permittivity of 35 and quality factor in excess of 25,000 GHz. The improvement in properties after annealing is primarily due to an increase in homogeneity.     

Microwave dielectric properties and low-temperature sintering of Ba3Ti4Nb4O21 ceramics with B2O3 and CuO additions

The low sintering temperature and the good dielectric properties such as high dielectric constant (ɛ_r), high quality factor (Q × f) and small temperature coefficient of resonant frequency (τ_f) are required for the application of chip passive components in the wireless communication technologies. In the present study, the sintering behaviors and dielectric properties of Ba₃Ti₄Nb₄O₂₁ ceramics were investigated as a function of B₂O₃–CuO content. Ba₃Ti₄Nb₄O₂₁ ceramics with B₂O₃ or CuO addition could be sintered above 1100 °C. However, the additions of both B₂O₃ and CuO successfully reduced the sintering temperature of Ba₃Ti₄Nb₄O₂₁ ceramics from 1350 to 900 °C without detriment to the microwave dielectric properties. From the X-ray diffraction (XRD) studies, the sintering behaviors and the microwave dielectric properties of low-fired Ba₃Ti₄Nb₄O₂₁ ceramics were examined and discussed in the formation of the secondary phases. The Ba₃Ti₄Nb₄O₂₁ sample with 1 wt% B₂O₃ and 3 wt% CuO addition, sintered at 900 °C for 2 h, had the good dielectric properties: ɛ_r = 65, Q × f = 16,000 GHz and τ_f = 101 ppm/°C.     

Effect of Li2O–V2O5 on the low temperature sintering and microwave dielectric properties of Li1.0Nb0.6Ti0.5O3 ceramics

Li₂O–Nb₂O₅–TiO₂ based ceramic systems have been the candidate materials for LTCC application, due to their high dielectric constant and Q × f value and controllable temperature coefficient in the microwave region. However, the sintering temperature was relatively higher (above 1100 °C) for practical application. In this study, dielectric properties of Li_(1+x−y)Nb_(1−x−3y)Ti_(x+4y)O₃ solid solution were studied with different x and y contents and among them, the Li_1.0Nb_0.6Ti_0.5O₃ composition (x = 0.1, y = 0.1) was selected, due to its reasonable dielectric properties to determine the possibility of low temperature sintering. The effects of 0.17Li₂O–0.83V₂O₅, as a sintering agent, on sinterability and microwave dielectric properties of Li_1.0Nb_0.6Ti_0.5O₃ ceramics were investigated as a function of the sintering agent content and sintering temperature. With addition of 0.17Li₂O–0.83V₂O₅ above 0.5 wt%, the specimens were well densified at a relatively lower temperature of 850 °C. Only slight decrease in apparent density was observed with increasing 0.17Li₂O–0.83V₂O₅ content above 0.75 wt%. In the case of 0.5 wt% 0.17Li₂O–0.83V₂O₅ addition, the values of dielectric constant and Q × f reached maximum. Further addition caused inferior microstructure, resulting in degraded dielectric properties. For the specimens with 0.5 wt% 0.17Li₂O–0.83V₂O₅ sintered at 850 °C, dielectric constant, Q × f and TCF values were 64.7, 5933 GHz and 9.4 ppm per °C, respectively.     

Effect of B2O3 on the sintering and microwave dielectric properties of M-phase LiNb0.6Ti0.5O3 ceramics

The effect of B₂O₃ addition on the sintering, microstructure and the microwave dielectric properties of LiNb_0.6Ti_0.5O₃ ceramics have been investigated. It is found that low-level doping of B₂O₃ (≤2 wt.%) can significantly improve the densification and dielectric properties of LiNb_0.6Ti_0.5O₃ ceramics. Due to the liquid phase effect of B₂O₃ addition, LiNb_0.6Ti_0.5O₃ ceramics could be sintered to a theoretical density higher than 95% even at 880 °C. No secondary phase was observed for the B₂O₃-doped ceramics. There is no obvious degradation in dielectric properties for the ceramics with B₂O₃ additions. In the case of 1 wt.% B₂O₃ addition, the ceramics sintered at 880 °C show good microwave dielectric properties of ɛ_r = 70, Q × f = 5400 GHz, τ_f = −6.39 ppm/°C. It represents that the ceramics could be promising for multilayer low-temperature co-fired ceramics (LTCC) applications.     

Microstructure and dielectric characteristics of Nb2O5 doped BaTiO3-Bi(Znl/2Til/2)O3 ceramics for capacitor applications

The effects of Nb₂O₅ addition on the dielectric properties and phase formation of 0.8BaTiO₃-0.2Bi(Zn_l/2Ti_l/2)O₃ (0.8BT-0.2BZT) ceramics were investigated. The desired perovskite phase was achieved with Nb₂O₅ doping levels being in the range of 0.5 wt.%–3.0 wt.%. The 0.8BT-0.2BZT ceramics doped with 1.5 wt.% Nb₂O₅ was found to possess a moderate dielectric constant (ε = 1170) and low dielectric loss (tanδ = 1%) at room temperature and 1 kHz frequency, showing a flat dielectric behavior over the temperature range of −55 °C–200 °C. Based on this composition, the X9R-MLCC (multilayer ceramic capacitor) with Ag0.7-Pd0.3 electrode was sintered at 1060 °C. The optimized capacitance of the MLCC is 26.5 nF, with dielectric loss tanδ of 0.9% and electrical resistance of 4.50 × 10¹¹ Ω at room temperature, leading to a high time constant of 11,900 s, decreasing to 175 s at 200 °C, being one order higher than those of commercial X7R MLCC. In addition, the equivalent series resistance (ESR) was found to be on the order of 0.2 mΩ at 2 MHz, much lower than that of the DC Bus Capacitor Bank for the automotive inverters (where the desired characteristic is <3 mΩ). All these characteristics of the newly developed MLCC will benefit the high temperature and high power capacitor applications.     

Structure and electrical properties of PZT–PMS–PZN piezoelectric ceramics

The quaternary piezoelectric ceramics of Pb(Zr_0.52Ti_0.48)O₃–Pb(Mn_1/3Sb_2/3)O₃–Pb(Zn_1/3Nb_2/3)O₃ (PZT–PMS–PZN) with different PZN contents were synthesized by molten salt synthesis (MSS). The influence of PZN content on phase structure, microstructure, dielectric and piezoelectric properties was investigated in detail. The results of X-ray diffraction (XRD) show that the phase structure of ceramics transforms from rhombohedral phase to tetragonal phase with the increasing of PZN content. The morphotropic phase boundary (MPB) of composition is located in the range of PZN content from 2 to 7 mol%. The grain size of the ceramics gradually decreases with the increasing of PZN content. Dielectric and piezoelectric properties of ceramics are significantly influenced by the PZN content. Ceramics sintered at 1150 °C with 5 mol% PZN achieve excellent properties, which are as follows: Q_m = 1381, K_p = 0.64, d₃₃ = 369pC/N, tan δ = 0.0044 and T_c = 275 °C. The PZT–PMS–PZN system is a promising material for high power piezoelectric transformers application.     

Microwave dielectric properties and microstructures of Nb2O5-Zn0.95Mg0.05TiO3 + 0.25TiO2 ceramics with Bi2O3 addition

The effects of Bi₂O₃ addition on the microwave dielectric properties and the microstructures of Nb₂O₅-Zn_0.95Mg_0.05TiO₃ + 0.25TiO₂ (Nb-ZMT′) ceramics prepared by conventional solid-state routes have been investigated. The results of X-ray diffraction (XRD) indicate the presence of four crystalline phases, ZnTiO₃, TiO₂, Bi₂Ti₂O₇, and (Bi_1.5Zn_0.5)(Ti_1.5Nb_0.5)O₇ in the sintered ceramics, depending upon the amount of Bi₂O₃ addition. In addition, in order to confirm the existence of (Bi_1.5Zn_0.5)(Ti_1.5Nb_0.5)O₇ phase in the samples, the microstructure of Nb-ZMT′ ceramic with 5 wt.% B₂O₃ addition was analyzed by using a transmission electron micrograph. The dielectric constant of Nb-ZMT′ samples was higher than ZMT′ ceramics. The Nb-ZMT′ ceramic with 5 wt.% Bi₂O₃ addition exhibits the optimum dielectric properties: Q × f = 12,000 GHz, ?_r = 30, and τ_f = ?12 ppm/°C. Unlike the ZMT′ ceramic sintered at 900 °C, the Nb-ZMT′ ceramics show higher Q value and dielectric constant. Moreover, there is no Zn₂TiO₄ existence at 960 °C sintering. To understand the co-sinterability between silver electrodes and the Nb-ZMT′ dielectrics, the multilayer samples are prepared by multilayer thick film processing. The co-sinterability (900 °C) between silver electrode and Nb-ZMT′ dielectric are well compatible, because there are no cracks, delaminations, and deformations in multilayer specimens.     

Microwave dielectric properties of Ca(Li1/4Nb3/4)O3–CaTiO3 ceramic systems

The microwave dielectric properties of Ca(Li_1/4Nb_3/4)O₃–CaTiO₃ ceramics have been investigated with regard to calcination temperature and the amount of CaTiO₃ additive. Ca(Li_1/4Nb_3/4)O₃ ceramics with an orthorhombic crystal structure can be synthesized by the conventional mixed oxide method by calcining at 750 °C and sintering at 1275 °C. The dielectric constant (ɛ_r), quality factor (Q × f₀) and temperature coefficient of resonant frequency (τ_f) for Ca(Li_1/4Nb_3/4)O₃ ceramics are 26, 13,000 GHz and −49 ± 2 ppm/°C, respectively. With increase in the CaTiO₃ content, ɛ_r and τ_f are increased and the quality factor decreased due to the solid-solution formation between Ca(Li_1/4Nb_3/4)O₃ and CaTiO₃. The 0.7Ca(Li_1/4Nb_3/4)O₃–0.3CaTiO₃ ceramic exhibits ɛ_r of 44, quality factor (Q × f₀) of 12,000 GHz and τ_f of −9 ± 1 ppm/°C.