B-site Bond Valence Research Articles

Crystal Structure and Microwave Dielectric Characteristics of Novel Ba(Eu1/5Sm1/5Nd1/5Pr1/5La1/5)2Ti4O12 High-Entropy Ceramic

High-permittivity Ba(Eu1/5Sm1/5Nd1/5Pr1/5La1/5)2Ti4O12 (BESNPLT) high-entropy ceramics (HECs) were synthesized via a solid-state route. The microstructure, sintering behavior, phase structure, vibration modes, and microwave dielectric characteristics of the BESNPLT HECs were thoroughly investigated. The phase structure of the BESNPLT HECs was confirmed to be a single-phase orthorhombic tungsten-bronze-type structure of Pnma space group. Permittivity (εr) was primarily influenced by polarizability and relative density. The quality factor (Q×f) exhibited a significant correlation with packing fraction, whereas the temperature coefficient (TCF) of the BESNPLT HECs closely depended on the tolerance factor and bond valence of B-site. The BESNPLT HECs sintered at 1400 °C, demonstrating high relative density (>97%) and optimum microwave dielectric characteristics with TCF = +38.9 ppm/°C, Q×f = 8069 GHz (@6.1 GHz), and εr = 87.26. This study indicates that high-entropy strategy was an efficient route in modifying the dielectric characteristics of tungsten-bronze-type microwave ceramics.

Crystal Structural Characteristics and Electrical Properties of (Ba0.7Sr0.3-xCax)(Ti0.9Zr0.1)O3 Ceramics Prepared Using the Citrate Gelation Method.

The electrical properties of (Ba0.7Sr0.3-xCax)(Ti0.9Zr0.1)O3 (0 ≤ x ≤ 0.2) (BSCTZ) ceramics prepared using citrate gelation (CG) method were investigated by substituting Ca2+ ions for the Sr2+ sites based on the structural characteristics of the ceramics. BSCTZ was sintered for 3 h at 1300 °C, lower than the temperature (1550 °C) at which the specimens prepared using the solid-state reaction (SSR) method were sintered, which lasted for 6 h. As the amount of substituted Ca2+ ions increased, the unit cell volume of the BSCTZ decreased because of the smaller ionic radius of the Ca2+ ions compared to the Sr2+ ions. The dielectric constant of BaTiO3-based ceramics is imparted by factors such as the tetragonality and B-site bond valence of the ceramics. Although the ceramic tetragonality increased with Ca2+ ion substitution, the x = 0.05 specimens exhibited the highest dielectric constant. The decrease in the dielectric constant of the sintered x > 0.05 specimens was attributed to the increase in the B-site bond valence of the ABO3 perovskite structure. Owing to the large number of grain boundaries, the breakdown voltage (6.6839 kV/mm) of the BSCTZ prepared using the CG method was significantly improved in relation to that (2.0043 kV/mm) of the specimen prepared using the SSR method.

Structure characteristics and microwave dielectric properties of Pr2(Zr1−Ti )3(MoO4)9 solid solution ceramic with a stable temperature coefficient

· The sintering temperature of Pr 2 (Zr 1− x Ti x ) 3 (MoO 4 ) 9 ceramic was below 900 °C. · Effect of bond characteristics on Pr 2 (Zr 1− x Ti x ) 3 (MoO 4 ) 9 were discussed. · Excellent temperature stability was obtained (−14.1 ∼ −2.6 ppm/ °C). Pr 2 (Zr 1− x Ti x ) 3 (MoO 4 ) 9 ( x = 0.1–1.0) ceramics were prepared via a conventional solid-state method, the dependence of crystal structure and bond characteristics on microwave dielectric properties was investigated systemically. The X-ray diffraction patterns indicated that the single-phase Pr 2 Zr 3 (MoO 4 ) 9 structure was formed in all the specimens. As the Ti 4+ content increased, the lattice volume gradually decreased, which was ascribed to the fact that the ionic radius of Ti 4+ was smaller than that of Zr 4+ . Notably, outstanding microwave dielectric properties with ε r of 10.73–16.35, Q · f values of 80,696–18,726 GHz and minor τ f values −14.1 – −2.6 ppm/ °C were achieved in Pr 2 (Zr 1− x Ti x ) 3 (MoO 4 ) 9 ceramics. The ε r increased with the rising x values, which was associated with the increase of α / V m values. The decreasing Q · f was affected by the decline of lattice energy of [Zr/TiO 6 ] octahedral. The τ f value was dominated by [Zr/TiO 6 ] octahedral distortion, Mo–O bond energy, bond strength and B-site bond valence. Furthermore, infrared reflection spectra suggested that the properties were mainly caused by the absorption of phonon, and the dielectric loss could be further reduced by optimizing the experimental process.

The structure evolution and lattice energy of spinel-structured Li(Mg0.5Ti0.5)xGa5−xO8 microwave dielectric ceramics

The microwave dielectric properties of spinel-structured Li(Mg0.5Ti0.5)xGa5−xO8 (0 ≤ x ≤ 1) ceramics were researched together with their microstructures. The X-ray diffraction and Raman spectroscopic revealed that an ordered spinel structure in 1: 3 B-site ordering with space group P4332 was formed in the composition range of 0 = x ≤ 0.25, and a disordered spinel with space group Fd-3m was formed in 0.5 = x ≤ 1. All the ceramics were compact with uniform grain, clear grain boundaries and high relative density (ρrelative ≥ 95 %). With the substitution of [Mg0.5Ti0.5]3+ for Ga3+ increased, the dielectric constant (εr) increased from 10.48 to 11.28, which was related to the increased molar ionic polarizability (αtheo/Vm) and B-site bond ionicity. The temperature coefficient of the resonant frequency (τf) slightly increased from −66.27 ppm/°C to −61.45 ppm/°C, due to the decrease of B-site bond valence. The Q × f value firstly decreased from 125,400 GHz to 50,381 GHz and then increased to 85,360 GHz, which was affected by the intrinsic loss analyzed by lattice energy. The optimal microwave dielectric properties were obtained for LiMg0.5Ti0.5Ga4O8 ceramic (x = 1) sintered at 1260 °C with εr = 11.28, Q × f = 85,360 GHz and τf = −61.45 ppm/°C.

Structures and microwave dielectric behavior of Sr0.1Ca0.9TiO3–Bi0.1Na0.1Li0.4Sm0.4TiO3 ceramic system

Microwave dielectric ceramics with xSr0.1Ca0.9TiO3–(1−x)Bi0.1Na0.1Li0.4Sm0.4TiO3 (xSCT–BNLST) compositions were prepared through the conventional oxide-state reaction. X-ray diffraction results showed that the symmetry in xSCT–BNLST system were improved with the increase of x. Based on the calculation results, the deviation of observed dielectric polarizabilities from theoretical values could be ascribed to the increase of A-site ionic polarizability and B-site bond valence. The decreased temperature coefficient of resonant frequency, τf, was dependent on the B-site bond valence in the tilted region. With the increase of temperature, the samples changed their main conductive carrier, from first ionization of oxygen vacancies to second ionization of oxygen vacancies. Optimum microwave dielectric properties were achieved, for 0.09SCT–BNLST ceramic with relative permittivity, er = 111, quality factor, Q × f = 3819 GHz and τf ~ 0 ppm/°C. The system has the potential for use in dielectrically loaded antennas and C0G high-frequency filter applications.

Microwave dielectric characteristics of high permittivity Ca0.35Li0.25Nd0.35Ti1-x(Zn1/3Ta2/3)xO3 ceramics (x = 0.00–0.12)

The Ca0.35Li0.25Nd0.35Ti1-x(Zn1/3Ta2/3)xO3 (0 ≤ x ≤ 0.12) ceramics were prepared using the solid-state reaction route. The influence of substitution of (Zn1/3Ta2/3)4+ for Ti4+ on microstructure and microwave dielectric properties of Ca0.35Li0.25Nd0.35Ti1-x(Zn1/3Ta2/3)xO3(CLNT(ZT)x) ceramics was investigated in this study. The X-ray diffraction patterns (XRD) of the specimens showed that the ceramics with x ≤ 0.06 were crystallized as an orthorhombic perovskite structure in Pnma space group. However, the secondary phase of Nd2Ti2O7 was observed with properties of 0.08 ≤ x ≤ 0.12. The analysis results of Raman spectra revealed the existence of oxygen octahedral distortion and the short-range ordering occurred in CLNT(ZT)x ceramics with the change of (Zn1/3Ta2/3)4+ content. The dielectric constant (εr) increased firstly and then decreased gradually when substitution increased, and the variation of εr was affected by the B-site bond valence. The quality factor value (Q × f) was improved by right amount of substitution when x ≤ 0.08, but deteriorated seriously as excessive (Zn1/3Ta2/3)4+ content was added (x ≥ 0.10). The temperature coefficient of the resonant frequency (τf) was effectively reduced from +90.9 ppm/ºC to +30.3 ppm/ºC with the increasing of substitution due to the declination of tolerant factor (t). At last, the CLNT(ZT)0.08 ceramics sintered at 1250 °C for 4 h exhibited the excellent comprehensive dielectric properties with εr = 120.63,Q × f = 3889 GHz, τf = +60.9 ppm/ºC.

Structure analysis and microwave dielectric properties of germanium ion-doped ZnZrNb2O8 ceramics

Germanium ion-doped ZnZrNb2O8 with composition of ZnZr1−xGexNb2O8 (x = 0.10, 0.20, 0.30, 0.35, 0.40) ceramics that exhibited improved Q × f value were first prepared by solid state method. X-ray diffraction (XRD) rietveld refinement was used to analyze the structure variations of the ceramic samples. The XRD patterns showed that all the samples contained the ZnZrNb2O8 phase with monoclinic structure. With the increase of germanium ion content, the dielectric constant decreased which was ascribed to the decrease of ionic polarizability. The improvement of Q × f value was mainly attributed to the increase of packing fraction. And, the emergence of the second phase also had a promoting effect to a certain extent. The temperature coefficient of resonant frequency (τ f ) correlated with the variation of bond valence of B-site. When x value exceeded 0.4, the microwave dielectric properties deteriorated seriously. The good combination microwave dielectric properties of e r = 23.7, Q × f = 89,341 GHz (where f = 8 GHz), and τ f = −65.48 ppm/°C were obtained for ZnZr1−xGexNb2O8 (x = 0.35) ceramics sintered at 1180 °C for 6 h.

High-Q microwave dielectric properties in the Na0.5Sm0.5TiO3 + Cr2O3 ceramics by one synthetic process

Abstract The Na0.5Sm0.5TiO3 + x mol Cr2O3 ceramics (x = 0, 0.25%, 0.5%, 0.75%, 1%, 1.25% and 1.5%) were conventionally prepared using solid-state reaction method by one synthesizing process. All specimens were identified as a structure of orthorhombic perovskite with Pnma space group. Both of XRD patterns and refinement results showed that the Cr3+ had incorporated into the lattice at Ti sites, leading to the expansion of cell volume. The densification can be improved by adding a proper amount of Cr2O3 (0.25% ≤ x ≤ 1%). The permittivity (er) slightly increased with x ≤ 0.25%, later decreased with further addition of Cr2O3, which showed a similar varying trend to dielectric polarizabilities. The temperature coefficient of the resonant frequency (τf) was reduced from 199.3 ppm/°C to 160.8 ppm/°C due to an increase of B-site bond valence. The experimental XPS results confirmed that there was a significant increase of quality factor (Q×f) from 8993 GHz at x = 0–11854 GHz at x = 1% due to the restraint of Ti4+ reduction to Ti3+. When added with 1% mol Cr2O3, the Na1/2Sm1/2TiO3 ceramic sintered at 1450 °C for 2 h exhibited high microwave dielectric properties of er = 96, Q×f = 11854 GHz and τf = 171.2 ppm/°C.

Low temperature sintering of high permittivity Ca-Li-Nd-Ti microwave dielectric ceramics with BaCu(B2O5) additives

In this paper, the influences of Al substitution and BaCu(B2O5) (BCB2) additives on the sintering temperature, microstructures, phase structures and microwave properties were investigated in detail. The results indicated that all Al added Ca0.35Li0.25Nd0.35Ti1-xAlxO3 (CLNTAx) samples were crystallized as orthorhombic perovskite structure in Pnma space group. A proper amount (x ≤ 0.03) of Al substitution for Ti was beneficial to improve the quality factors mainly due to the increase of packing fraction. But the permittivity (εr) and temperature coefficient of the resonant frequency (τf) deteriorated because of the decrease of B-site bond valence. The perovskite structured phase and BCB2 phase were observed in Ca0.35Li0.25Nd0.35Ti0.97Al0.03O3 (CLNTA3) ceramics, when a small amount of BCB2 was added (y ≤ 5 wt%). The sintering temperature was effectively lowered under 950 °C, and τf was modified from 74.8 ppm/°C to 41.2 ppm/°C with the assistance of BCB2 phase and liquid phase. But excessive BCB2 contents (y > 5 wt%) resulted in the BaNd2Ti5O14 and unknown phase, leading to inferior dielectric properties. Therefore, 5 wt% BCB2-added CLNTA3 ceramics sintered at 950 °C for 2 h exhibited excellent comprehensive microwave dielectric properties: εr = 109.5, Q × f = 2979 GHz and τf = 41.2 ppm/°C.

Effect of NdAlO3 on microstructure, dielectric properties and temperature-stable mechanism of (Sr, Ca, Nd)TiO3 ceramics at microwave frequency

Microwave dielectric ceramics (1 − x)(Sr0.3Ca0.427Nd0.182)TiO3–xNdAlO3 (abbreviated as SCNTAx hereafter, 0.1 ≤ x ≤ 0.4) were prepared by conventional mixed oxide route, and their phase composition, microstructure and microwave dielectric properties were investigated as a function of the x value and sintering temperatures. A single tilted orthorhombic perovskite structure in space group Pnma was refined in the studied composition range. For microware dielectric properties, the decreasing relative permittivity was strongly affected by the ionic polarizability of Nd3+ and Al3+ in SCNTAx ceramic systems. Also, the quality factor of SCNTAx solid solution had strongly depended on apparent densities and average grain sizes. As expected, the promising ceramic of SCNTAx (x = 0.25) sintered at 1520 °C for 4 h was found to possess good microwave dielectric properties: a relative permittivity (er) of 55.6, a quality factor (Q × f) of 25,600 GHz (at 4.249 GHz) and a temperature coefficient of resonant frequency (τf) of 6.7 ppm/°C. Especially, the τf values of SCNTAx ceramics were not strongly depended on tolerance factor (t) with increasing of the NdAlO3 content, while these τf values were essentially correlated with the B-site bond valence and octahedral tilting. Wherein, either decreasing the B-site bond valence or increasing the octahedral tiltings (θ and φ) led to a decrease in τf value for the present ceramics.

Microwave dielectric properties of sol-gel derived CoTiNb2O8 ceramics

CoTiNb2O8 microwave dielectric ceramics were synthesized via a modified sol-gel route. The thermal decomposition behavior of the as-prepared precursor was characterized by differential thermal analysis (DTA)/thermogravimetry (TG). Highly reactive CoTiNb2O8 nano-powders with average particle size of 34 nm were achieved by the reaction between TiO2 and intermediate phase CoNb2O6 at 800 °C. The microwave dielectric properties of ceramics were sensitive to processing condition and crystal structure. For the CoTiNb2O8 compounds, the variations of εr and Q × f value agreed well with that of the relative density. The τf was explained in terms of oxygen octahedral distortion and B-site bond valence. At 1000°C/4h, CoTiNb2O8 ceramic possessed optimal microwave dielectric properties with an εr of 64.19, a high Q × f of 16,800 GHz (at 6.4 GHz) and a τf of 66.17 ppm/°C.

Crystal structure and microwave dielectric properties of the low dielectric loss ZnZr1−xSnxNb2O8 ceramics

ZnZr1−xSnxNb2O8 (x=0.10, 0.15, 0.20, and 0.25) ceramics with improved microwave dielectric properties were prepared by conventional mixed oxide route. The effects of Sn4+ ion substitution on the microwave dielectric properties based on structural characteristics in this system were investigated systematically. Rietveld refinement was used to analyze the structure change of the sintered samples. Microscopic analysis showed that all the samples maintained the ZnZrNb2O8 phase with monoclinic structure. With the increase of Sn4+ content, the dielectric constant decreased attributed to the decrease of ionic polarizability. The Q×f value was dependent on, and increased monotonically with packing fraction. The temperature coefficient of resonant frequency (τf) correlated with the variation of bond valence of B-site. The excellent microwave dielectric properties of εr=27.37, Q×f=76,814GHz (where f=7GHz), and τf=−55.09ppm/°C were obtained for ZnZr1−xSnxNb2O8 (x=0.20) ceramics sintered at 1275°C for 6h.

Crystal structure and microwave dielectric characteristics of Zr-substituted CoTiNb2O8 ceramics

Co(Ti1-xZrx)Nb2O8 microwave dielectric ceramics were synthesized via the conventional solid-state reaction route. The dependence of microwave dielectric properties on the crystal structure was discussed. The phase transitions were analyzed using X-ray powder diffraction, Raman spectroscopy, and transmission electron microscopy. A series of composition-induced phase transitions were confirmed via the sequence: tetragonal rutile structure→coexistence of rutile and wolframite phase→monoclinic wolframite structure. For the Co(Ti1-xZrx)Nb2O8 compounds, Zr substitutions from 0 to 1 led to a decrease in the εr from 62.4 to 23.8. In contrast to εr, Q×f increased considerably, which was explained in terms of packing fraction. The τf was correlated with oxygen octahedral distortion and B-site bond valence. A near zero τf of 4.4ppm/°C was obtained in the CoTi0.4Zr0.6Nb2O8 ceramics with an εr of 29.9 and a high Q×f of 72,833GHz.

A new microwave dielectric material ZnZr0.8Sn0.2Nb2O8

A novel low-loss microwave dielectric material ZnZr0.8Sn0.2Nb2O8 was reported for the first time. The samples were prepared by the conventional solid-state reaction route and sintered in the temperature range of 1225–1325 °C for 6 h. Single phase ZnZr0.8Sn0.2Nb2O8 was obtained and it showed monoclinic structure. The microstructure and microwave dielectric properties were investigated systematically. The variation trend of dielectric constant (e r ) was in accordance with variation trend of relative density. The Qf value mainly depended on the crystal structure and it increased with the increasing packing fraction. The temperature coefficient of resonant frequency (τ f ) correlated with the variation of bond valence of B-site. The excellent microwave dielectric properties of e r = 27.37, Q × f = 76,814 GHz (where f = 7 GHz), and τ f = −55.09 × 10−6/ °C were obtained for ZnZr0.8Sn0.2Nb2O8 ceramics sintered at 1275 °C for 6 h.

Microstructure and microwave dielectric characteristics of (Zn1−xCox)ZrNb2O8 ceramics

The (Zn1−xCox)ZrNb2O8 (x = 0.1, 0.2, 0.3, 0.4) ceramics were synthesized by the conventional solid-state reaction route and sintered in the temperature range of 1160–1320 °C. The microstructure and microwave dielectric properties were investigated systematically. The X-ray diffraction results showed that the (Zn1−xCox)ZrNb2O8 ceramics exhibited a single monoclinic structure. The variation trend of dielectric constant (er) was in accordance with variation trend of relative density. The Qf value decreased with the decrease of the packing fraction. The temperature coefficient of resonant frequency (τf) moved towards positive due to the increase of B-site bond valence. In conclusion, the excellent microwave dielectric properties were obtained for Zn0.9Co0.1ZrNb2O8 ceramics sintered at 1240 °C for 4 h: er = 27.93, Q × f = 68,615 GHz (where f = 6.95 GHz), and τf = −61.94 × 10−6/°C.

Microstructures and microwave dielectric properties of (1 − x)Sr0.2Na0.4Sm0.4TiO3–xLnAlO3 (Ln = Nd, Pr and Sm) ceramic systems

The microstructures and microwave dielectric properties of the (1 − x)Sr0.2Na0.4Sm0.4TiO3–xLnAlO3 samples (where Ln stands for Nd, Pr and Sm, x = 0.2–0.3) were studied. The XRD result showed that the (1 − x)Sr0.2Na0.4Sm0.4TiO3–xLnAlO3 (Ln = Nd, Pr and Sm) solid-solutions with single orthorhombic perovskite phase could be formed in the componential range of 0.2 ≤ x ≤ 0.3. With an increasing of Ln3+ content, the dielectric constant (e r ) decreased due to the smaller dielectric polarizability of LnAlO3 than that of Sr0.2Na0.4Sm0.4TiO3. With increasing x from 0.2 to 0.3, the quality factor (Q·f) firstly increased and then decreased for the specimens with PrAlO3, because the Q·f values were strongly depended on grain sizes. Moreover, either increasing the A-site bond valence or decreasing the B-site bond valence led to a decrease in the temperature coefficient of the resonant frequency (τ f). Typical values of e r ~ 52.7, Q·f ~ 9700 GHz (at 4.33 GHz) and τ f ~ 1.5 ppm/°C were obtained for the (1 − x)Sr0.2Na0.4Sm0.4TiO3–xSmAlO3 (x = 0.25) ceramic sintered at 1470 °C for 4 h.

Microstructure and Microwave Dielectric Properties of Ba3.75Nd9.5Ti18−z (Mg1/3Nb2/3) z O54 Ceramics

The effects of magnesium and niobium substitution for titanium on the microwave dielectric properties of Ba3.75Nd9.5Ti18−z (Mg1/3Nb2/3) z O54 (0 ≤ z ≤ 3) ceramics were studied. The temperature coefficient of resonant frequency (τ f ) decreased from about +60 ppm/°C to +17 ppm/°C when z ≤ 1. Excellent quality factor (Qf = 7300 GHz) as well as high dielectric constant (ε r = 80.96) were obtained. For z ≥ 1.5, Nd2(Ti,Mg,Nb)2O7 secondary phase appeared which would obviously influence the microwave dielectric properties. As z varied from 0 to 3, matrix grain size degraded which would obviously deteriorate the microwave dielectric properties by conducting more pores, especially the Qf value. The τ f value was found to be related to b-site bond valence (V B-O) and unit cell volume (V m). Average ionic polarizability (α D) and relative density evidently influenced the dielectric constant.

A microwave dielectric material Mg0.5Zn0.5ZrNb2O8

A high quality microwave dielectric material Mg0.5Zn0.5ZrNb2O8 was reported in this paper. Single-phase Mg0.5Zn0.5ZrNb2O8 was prepared by a conventional mixed-oxide route and sintered in the temperature range of 1220−1300°C. The microstructure and microwave dielectric properties were investigated systematically. The X-ray diffraction results showed that all samples exhibit a single monoclinic structure. The variation trend of dielectric constant was in accordance with that of relative density. The Qf value mainly depended on the crystal structure, and it increased with the increasing packing fraction. The temperature coefficient of τf correlated with the variation of bond valence of B-site. In summary, the monoclinic structure Mg0.5Zn0.5ZrNb2O8 ceramic samples sintered at 1260°C exhibited uniform and dense microstructural morphology, and owned outstanding microwave dielectric properties of ε=27.06, Qf=91077GHz, τf=−18×10−6/°C. These represent very promising candidates for the application of highly selective microwave ceramic resonators and filters.

Aluminum substitution for titanium in Ba3.75Nd9.5Ti18O54 microwave dielectric ceramics

Effects of aluminum substitution for titanium on microwave dielectric properties of Ba3.75Nd9.5Ti18−zAlzO54 (z = 0–3.0) ceramics were investigated in this study. X-ray diffraction patterns of sintered samples revealed single-phase formation with an orthorhombic structure of all compositions. Scanning electron microscopy (SEM) and energy dispersive spectrometer results confirmed the substitution at b-site. A small amount of aluminum substitution into b-site lead to the decrease of relative dielectric constant (er) and temperature coefficient of resonant frequency (τf), but significantly improved the quality factor (Qf). Further aluminum substitution content of z ≥ 1.5 resulted in the drop of Qf value and restraint of Ti reduction. Excellent microwave dielectric properties with z = 1.5 sintered at 1,350 °C for 2 h in air would be obtained: er = 72.7, Qf = 13,112 GHz and τf = +5 ppm/°C. Tolerance factor, electronegativity difference, ionic polarizability and b-site bond valence were calculated to clarify the relationship between microstructure and microwave dielectric properties.

Crystal structure and dielectric properties of (1−x)SrTiO3-xCa0.4Sm0.4TiO3 ceramic system at microwave frequencies

(1−x)SrTiO3-xCa0.4Sm0.4TiO3 (0.6 ≤ x ≤ 0.9) ceramics are prepared through the conventional solid-state route. Powders are calcined at 1200 °C and sintered at 1400–1500 °C. High density, CaTiO3-like perovskite structures are obtained in the range 0.6 ≤ x ≤ 0.9. The phase purity, microstructures and microwave dielectric properties are investigated. With an increase of Ca0.4Sm0.4TiO3 content, the dielectric constant (εr) decreases, which is dependent on the difference of ionic polarizability between Ca0.4Sm0.4TiO3 and SrTiO3. The product of dielectric Q value and resonant frequency (Q∙f) increases up to x = 0.8, and then decreases due to the abnormal grain growth. The variation of temperature coefficient of resonant frequency (τf) with B-site bond valence and tolerance factor (t) is discussed by using the theory of bond valence and the changes of tolerance factor in perovskite structure. The (1−x)SrTiO3-xCa0.4Sm0.4TiO3 (0.6 ≤ x ≤ 0.9) ceramics show the dielectric properties of εr ∼ 101.4–142.7, Q∙f ∼ 1999.5–5986.3 GHz (at 2.8–4 GHz) and τf ∼ 359.8–199.6 ppm/°C at different sintering temperatures of 1400–1500 °C for 4 h.