Conventional Solid-state Sintering Technique Research Articles

Effect of Sc2O3 doping on the microstructure and electrical characteristics of ZnO linear resistors

Herein, to improve the electrical characteristics, ZnO linear resistors mixed with MgO, TiO2, Al2O3, and various concentrations of Sc2O3 (with 0, 0.35, 0.7, and 1.05 wt %) were obtained using the conventional solid-state sintering technique, while the influences of Sc2O3 doping on the micro-morphology and electrical characteristics was investigated in detail. The crystalline phases and microstructure were investigated by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). The dielectric properties and electrical characteristics were evaluated using a precision inductance-capacitance-resistance meter and a high-voltage source meter. Results from SEM micrographs, XRD patterns, and EDS mappings illustrated that the doping of Sc2O3 hinders the growth of ZnO grains. Electric field-current density and resistivity-frequency measurements illustrated that the doping of Sc2O3 improves the linear performance of ZnO linear resistors and increases its grain resistivity and grain boundary resistivity. With Sc2O3 doping, the dielectric properties of the samples are significantly affected, while the resistance-temperature features reveal the negative temperature constant function. By appropriate Sc2O3 doping, the ZnO linear resistors exhibited excellent performance with grain boundary barrier height φb of 0.0106 eV, nonlinear coefficient α of 1.03, and resistance temperature constant αT of −2.88 × 10−3. It is beneficial to investigate the influence of Sc2O3 doping on the micro-morphology and electrical performances in detail for the preparation of zinc oxide linear resistors with superior performance.

Structural and dielectric properties of pure potassium sodium niobate (KNN) lead free ceramics

Lead free KNN (K0·5Na0·5NbO3) ceramics was obtained via the conventional solid state sintering technique. The ceramics synthesized was characterized for their phase transition analysis, crystal structure, morphology and electrical properties. The powder X-ray diffraction (XRD) patterns confirmed single phase of KNN with orthorhombic crystal system at room temperature. Scanning electron microscopy (SEM) of the sintered KNN revealed the existence of densification and comparable size of the grains. Two phase transitions were observed in ϵr-T graph: orthorhombic to tetragonal at TO-T (~236 °C) and tetragonal to cubic at TT-C (~440 °C) for 1 kHz frequency. The decrease in the net polarization of the material with the increase in frequency leads to the decrease in the value of ϵr and tanδ. Three characteristic Raman peaks observed at (~262 cm−1, ~617 cm−1 and ~858 cm−1) correlate the structure and ferroelectric properties of KNN materials. These promising outcomes demonstrate that KNN-based lead-free ceramic composition is potential candidate to substitute lead-based materials for various applications.

Microwave dielectric properties of BaWO4-doped Ba(Mg1/3Nb2/3)O3 ceramics

In this paper, Ba(Mg1/3Nb2/3)O3 (BMN) ceramics with x (x = 0–9) wt% BaWO4 were synthesized using the conventional solid-state sintering technique. Effects of BaWO4 addition on the microstructure and microwave dielectric properties of BMN ceramics were evaluated. X-ray diffraction (XRD) analysis showed that there were three phases: main crystalline phase Ba(Mg1/3Nb2/3)O3 and secondary phases BaWO4 and Ba5Nb4O15. Meanwhile, the (100) super-lattice reflection peaks shifted to a higher 2θ angle with increasing BaWO4 content. SEM photographs suggested that BaWO4 working as a sintering additive promoted the densification and grain growth. The dielectric properties were examined by Vector network analyzer. The dielectric constant (er) was largely determined by the relative density and phase composition. Meanwhile, the addition of BaWO4 had a positive effect on the Q × f value, for example the specimen with x = 5 possessed the highest Q × f value of 111,300 GHz. Optimum microwave dielectric properties (er = 31.7, Q × f = 111,300 GHz (f = 8 GHz) and τf = 0.16 ppm/°C) were obtained for the specimen with x = 5 sintered at 1350 °C for 6 h.

Effect of bismuth doping on structural and electrical properties of 0.9(BaZr0.2Ti0.8O3)–0.1(Ba0.7Ca0.3TiO3) ceramic

The (Ba0.97Ca0.03)1−3y/2BiyZr0.18Ti0.82O3 ceramic system was prepared by the conventional solid-state sintering technique. The effect of bismuth substitution has been investigated via X-ray diffraction, Scanning electron microscopy, dielectric, electric and ferroelectric measurements. X-ray diffraction showed that these compounds crystallized, at room temperature, in tetragonal P4mm space group symmetry for BCTZ10 and BCTZ10–0.02Bi compounds and in cubic symmetry with space group Pm3‾m for y = 0.06; 0.08 and 0.1 compositions distorted perovskite structures. SEM images were used to observe the microstructure. The effect of the crystal structure change and microstructure features on the dielectric and ferroelectric properties of our new BCTZ10-yBi ceramic system has been discussed. The dependence of the permittivity on temperature indicated a crossover from a normal ferroelectric, for both BCTZ10 and BCTZ10–0.02 ceramics, to a relaxor state for 0.06 < y ≤ 0.1 composition compounds. The enhancement of the dielectric properties was marked by the shift of Tm to room temperature, the increase of the maxim of permittivity and the improvement of the relaxor behavior that characterizes optimal composition due to Bi3+ substitution. BCTZ10–0.06Bi ceramic exhibit the highest εrm', with a value of 11508 at 1 kHz, at Tm of 270 k near room temperature. Both BCZT10 and BCZT-0.02Bi ceramics exhibit a hysteresis loops signature of ferroelectric behavior at room temperature. While doped BCZT-0.02Bi show just a non linear evolution of P vs. E, the increase of the spontaneous and remnant polarizations: Ps from 0.063 μC/mm2 to 0.073 μC/mm2 and Pr from 0.028 μC/mm2 to 0.040 μC/mm2 for BCZT10 and BCZT10–0.02Bi compositions, respectively, is an evidence of the enhancement of ferroelectric properties as a result of bismuth substitution on BCZT10. The electrical properties of our new BCTZ10-yBi ceramic system may be largely tunable and could be attractive for non-volatile random access memory devices.

Fabrication, microstructure and optical properties of large-sized Nd:YAG and composite Yb:YAG transparent ceramic slabs

Abstract Large-sized Nd:YAG and composite Yb:YAG transparent ceramic slabs of high quality were fabricated by the conventional solid-state reaction sintering technique. The Yb:YAG transparent ceramic slabs were surrounded by undoped YAG transparent ceramics and this composite structure was built in the process of ceramic shaping. The difference in microstructure between Yb:YAG and YAG transparent ceramics was not observed and the composite Yb:YAG slabs showed fully dense and pore-free microstructure. The in-line transmittances at 400 nm reached 81.7% and 79.7 % for YAG and Yb:YAG transparent ceramics, respectively, indicating good optical quality of the composite ceramic slab. And the optical transmission micrograph was very homogeneous with only a few isolated scattering centers. These results suggested that building composite structure in the process of ceramic shaping was a simple and reliable technical scheme. Moreover, the large-sized Nd:YAG transparent ceramic slab with size of 150.0 mm × 50.0 mm × 4.0 mm was also prepared. The calculated absorption coefficient was about 0.002 cm-1 @1064 nm, which suggested that the optical quality of this Nd:YAG transparent ceramic slab had reached the level of Nd:YAG crystals.

Phase characteristics, microstructure, and electrical properties of (1-x)BaZr0.2Ti0.8O3-(x)(Ba0.7Ca0.3)0.985La0.01TiO3 ceramics

Abstract In this study, (1-x)BaZr0.2Ti0.8O3-(x)(Ba0.7Ca0.3)0.985La0.01TiO3 ((1-x)BZT-(x)BCLT) ceramics, where x = 0.3, 0.4, 0.5, and 0.6, were prepared employing a conventional solid-state sintering technique. X-ray diffraction patterns and dielectric measurements indicated three phase regions at room temperature, including a single rhombohedral (x = 0.3), a phase coexistence of rhombohedral and tetragonal (x = 0.4), and a single tetragonal structure (x ≥ 0.5). X-ray photoemission spectra at the surface of ceramics confirmed the oxidation state of Ba2+, Ca2+, Ti4+, and Zr4+ ions. Upon BCLT addition, the reduction of the average grain size and the presence of the tetragonal structure significantly affected the dielectric, ferroelectric, and piezoelectric properties of these ceramics. With these results, the composition x = 0.3 showed maximum er′ and em′, whereas the composition x = 0.5 showed maximum Pr, Ec, d33, kp, and d∗33 factors. These results suggest a new phase diagram for the (1-x)BZT-(x)BCLT system, which could be tuneable by BCLT concentration and might be useful as an alternative material in dielectric, ferroelectric, and piezoelectric devices.

Effect of Sintering Temperature on Mechanical and Electrical Properties of Lead-Free Bi&lt;sub&gt;0.5&lt;/sub&gt;(Na&lt;sub&gt;0.4&lt;/sub&gt;K&lt;sub&gt;0.1&lt;/sub&gt;)Ti&lt;sub&gt;0.98&lt;/sub&gt;Zr&lt;sub&gt;0.02&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Piezoelectric Ceramics

Effect of sintering temperatures on phase formation, mechanical and electrical properties of lead-free Bi0.5(Na0.8K0.2)0.5Ti0.98Zr0.02O3 or BNKTZ piezoelectric ceramics were investigated. The BNKTZ ceramics were prepared via a conventional solid-state sintering technique under various sintering temperature range 1100-1150°C for 2 h. The phase formation and microstructure of the ceramics were examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM) method, respectively. XRD analysis indicated that all samples exhibited a single perovskite structure and no secondary phase. SEM microscopy study revealed an increase in grain size with increasing sintering temperature. The maximum values of density and maximum dielectric constant of the ceramics sintered at 1125 °C were 5.79 g/cm3 and 3446, respectively. In addition, the ceramics sintered at 1125 °C showed highest mechanical properties (HV = 4.32 GPa, HK = 5.87 GPa, E = 143 GPa and KIC = 1.30 MPa.m1/2). The highest values of ferroelectric and piezoelectric were found at this sintering temperature.

Thermoelectric Properties of YBa2Cu3O7−x-Ca3Co4O9 Segmented Oxide Ceramic

YBa2Cu3O7-x-Ca3Co4O9 (YBCO-CCO) segmented ceramic was prepared successfully using a conventional solid state sintering technique. X-ray diffraction patterns and microstructural observation indicated phase purity and a compatibility of YBCO and CCO ceramics. The maximum values of electrical conductivity (σ), Seebeck coefficient (S) and figure of merit (ZT) of YBCO-CCO segmented ceramic were 1.23 × 104 Ω−1 m−1, 179 μV/K and 0.35, respectively. Meanwhile, the thermal conductivity (κ) values of these three compounds were not significantly different and possessed small temperature dependence. The enhancement in the ZT values of YBCO-CCO segmented ceramic at high temperature compared to the conventional CCO ceramic suggested that the former might be used as an alternative p-type material for thermoelectric devices.

Influence of Microstructural Effect on Microvickers Hardness Properties of SiO2-Na2O-CaO (SNC) Waste Based Glass-ceramic

There are a lot of waste materials consist of silicate based such as coal combustion ash, slag from steel production, fly ash, mud, as well as glass cullet or mixtures to produce glass-ceramics. This research work using clam shell (CS) ash and soda-lime-silica (SLS) waste glass powder for fabricating novel SiO2-Na2O-CaO (SNC) glass-ceramic. The samples were composed of SLS (50%), Na2CO3 (30%), and CS (20%) in weight percentage via conventional melt-quenching technique and solid-state sintering technique. The samples were investigated via X-Ray Diffractometer (XRD), Field emission microscope (FESEM), and microvickers hardness tester. The samples were sintered at 550-950 °C to investigate the influence of microstructural effect on microvickers hardness properties at applied force 0.5 and 1.0 kgf. The optimal Vickers hardness properties at sintering temperature 850 °C due to high crystallization of SiO2 phase from the residual glass and CaO content enhanced the viscosity flow, high compactness of particles arrangement and densification of sample.

Dielectric, ferroelectric and piezoelectric properties of (Ba0.7Ca0.3)Ti1-xCuxO3-x ceramics

(Ba0.7Ca0.3)Ti1-xCuxO3-x ceramics (where x = 0, 0.01, 0.02 and 0.03) were prepared employing a conventional solid state sintering technique. X-ray diffraction patterns and Ti K-edge X-ray Absorption Near-Edge Structure (XANES) spectra indicated a structural distortion of Cu-doped ceramics. Depending on Cu content, the features of normal ferroelectric and diffuse dielectric phase transition could be induced by the Cu addition. The temperature where maximum dielectric existed was decreased upon increase of Cu concentration. The creation of oxygen vacancies and defect dipoles caused double-like P-E loop in host material. The decrease of d33, g33 and kp values was observed in correlation with decrease of Pr in doped ceramics. The results here suggested that the electrical properties of this ceramic system may be largely tunable by Cu dopant and could be an attractive material for high-dielectric response devices.

Relationship between the structure and microwave dielectric properties of non-stoichiometric Li2+xSiO3 ceramics

Li2SiO3 ceramic is one of the most important candidate materials for high-frequency microwave ceramics; however, minimal information about the relationship between the structure and microwave dielectric properties of non-stoichiometric Li2+xSiO3 ceramics is available. In the present work, nominal Li2+xSiO3 (x=0, 0.04, 0.08, 0.12 and 0.16) ceramics were prepared by a conventional solid-state sintering technique. The structure of Li2+xSiO3 ceramics was investigated via X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) as well as Raman spectra experiment and calculation. Refinements showed that part of the non-stoichiometric Li ions entered the Li2SiO3 lattice. Along with the results of the XRD analysis, Raman spectra experiment and calculation confirmed the presence of Li2Si2O5 phase in all the samples. Compared with stoichiometric Li2SiO3, non-stoichiometric Li provided higher densification and less ordering. Moreover, the SiO4 tetrahedrons formed more ionic bonds, which reduced distortion polarization. Further, the dielectric constants, which were observed to be mainly dependent on distortion polarization and densification, firstly increased then decreased slightly with increasing non-stoichiometric Li content. However, the quality factor (Q×f), which was primarily driven by ordering degree of Li-O bonds, firstly decreased then increased with increasing non-stoichiometric Li content. The results obtained on the Li2+xSiO3 ceramics, might offer some useful information for study and application about high-frequency microwave.

Effect of sintering temperature on structural and dielectric properties of Bi and Li co-substituted barium titanate ceramic

Bi and Li co-substituted barium titanate, Ba0.98(Bi,Li)0.02TiO3 ceramic samples were sintered at different temperatures using conventional solid state sintering technique. X-Ray Diffraction patterns confirm tetragonal phase in all the sintered samples. Microstructure analysis using Scanning Electron Microscopy (SEM) reveals increasing grain sizes with an increase in sintering temperature. Dielectric spectroscopy performed in the range of 40Hz to 2MHz at room temperature shows that the dielectric constant increases with increasing sintering temperature, reaching a maximum of value of 1200 at 40Hz where the dielectric loss observed was less than 0.02 for samples sintered at 1300°C. Temperature dependant impedance spectroscopy data in the range of 30–300°C was used to measure AC conductivity. The activation energy of grains was deduced through Arrhenius plots. Loss tangent at different frequencies for 1300°C sintered samples was less than 0.1 over the entire temperature range. The high dielectric constant with a low dielectric loss at elevated temperatures make Ba0.98(Bi,Li)0.02TiO3 samples suitable for Multi-Layer Ceramic Capacitors (MLCC)s used in high-temperature applications.

Effects of calcining temperature on crystal structures, dielectric properties and lattice vibrational modes of Ba(Mg1/3Ta2/3)O3 ceramics

Ba(Mg1/3Ta2/3)O3 ceramics were synthesized via a conventional solid-state sintering technique, calcined at 1200 °C (Y1), 1250 °C (Y2), and 1280 °C (Y3) for 2 h, separately, and next sintered at 1490 °C for 3 h. The main phase of BMT ceramics is a hexagonal structure \(\upsilon (\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {r} )\) (164) with 1:2 ordered structure. The intensities of the superlattice diffraction peaks (001) and (100) decrease with the increase in the calcining temperature, and the diffraction peaks’ intensities of the main phase also decrease, accordingly. The baseline of Y1 and Y2 are smooth, while that of Y3 is wavily, even some new modes appear, which is due to lower ordering degree. All in all, 1200 °C (Y2) and 1250 °C (Y3) are the better calcining temperatures because they possess better dielectric properties. Ten far-infrared modes are observed for Y2 sample, which are divided into three sections, including I section: the modes below 160 cm−1 being related to the vibration between Ba2+ and the (MgTa)O6 octahedron; II section: the modes between 180 and 300 cm−1 being mostly concerned with the (MgTa)-O and (WTa)-O stretching modes; III section: the modes above 500 cm−1 being related to the O-(MgTa)-O bending modes.

Analysis of the levitation force of pure and starch/polystyrene/MWCNT added bulk MgB2 superconductors using frozen image model under zero field cooling condition

The measurement of superconducting levitation force between permanent magnet and polycrystalline samples of pure and MgB2 added with starch, polystyrene (PS) and multiwall carbon nanotube (MWCNT) have been performed under zero field cooling (ZFC) condition at 20K in both descending and ascending modes. For this, the bulk pellets were synthesized by conventional solid state sintering technique. The XRD data indicate well developed MgB2 phase. However, a decrease in lattice parameter ‘a=b’ have been observed for doped MgB2 samples. Superconducting transition temperature of MgB2 also decreases with starch/PS/MWCNT addition. Unlike MWCNT, the addition of starch/polystyrene is found to enhance the levitation force of MgB2 superconductor. The levitation force between PM and investigated pellets in ZFC condition is explained well in terms of the updated version of modified frozen image model and the magnetic moment originated due to vertical motion of the superconductors have been estimated. It may be noted that except for MWCNT, addition of starch/PS in MgB2 improves the magnetic moment generated by vertical movement of pure MgB2. However, this improvement is more pronounced for 1wt.% of PS added MgB2, which indicates more flux trapping and hence better levitation properties in 1wt.% of PS added MgB2. The vertical stiffness estimated for pure and starch/PS/MWCNT doped MgB2 samples indicate that the levitation force are more sensitive in the region close to the PM.

The inferences of ZnO additions for LKNNT lead-free piezoelectric ceramics

ABSTRACTBy the conventional solid-state liquid-phase sintering technique, Li0.058(K0.480Na0.535)0.966(Nb0.9Ta0.1)O3 + x wt% ZnO (x = 0, 0.2, 0.4, 0.6, 0.8, 1, 3) lead-free piezoelectric ceramics were fabricated. The addition of ZnO liquid-phase sintering promoters could improve the grain-growth of LKNNT ceramics significantly and its inferences were investigated detailed in this paper. The crystal phases and micro-structures were analyzed by means of the X-ray diffraction and scanning electronic microscopy, respectively. Using the impedance analyzer, the dielectric constant, loss tangent, Curie temperature, phase transition point, and electromechanical coupling factor were measured. And the piezoelectric constants were measured by the d33 meter. Compared to pure LKNNT ceramic (sintered at 1090°C, d33 = 279 pC/N, and kp = 0.46), for x = 0.6 specimen, even though the optimal d33 and kp values were only 272 pC/N and kp = 0.44, but the optimal sintering temperature have been improved from 1090°C to 1020°C successfully.

Correlation among far-infrared reflection modes, crystal structures and dielectric properties of Ba(Zn1/3Nb2/3)O3–CaTiO3 ceramics

Ba(Zn1/3Nb2/3)O3 (BZN)–CaTiO3 (CT) microwave dielectric ceramics were synthesized at 1395°C for 4h using conventional solid-state sintering technique with different CT contents. The ceramics were characterized by X-ray diffraction (XRD) and far-infrared reflection (FIR) spectroscopy to evaluate correlations among crystal structures, dielectric properties, and infrared modes. XRD results showed that crystal symmetry decreased with increased CT concentration from cubic to hexagonal structure, and lattice constants and ordered degree changed accordingly. Ordered phases transformed from 1:1 to 1:2 ordered structure with crystal-structure change. FIR results demonstrated that two new IR active modes appeared at 300cm−1, and another new mode appeared at 600cm−1 for the x≥0.60 sample, which agreed with the change in crystal structures as confirmed by XRD results. Correlations between FIR modes and dielectric properties were established.

Effects of PbO-B2O3 Glass Doping on the Sintering Temperature and Piezoelectric Properties of 0.35Pb (Ni1/3Nb2/3)O3-0.65Pb(Zr0.41Ti0.59)O3 Ceramics

0.35Pb(Ni1/3Nb2/3)O3-0.65Pb(Zr0.41Ti0.59)O3 (PNN-PZT) ceramics doped with 0.5PbO-0.5B2O3 glass have been synthesized by the conventional solid-state sintering technique. The effects of 0.5PbO-0.5B2O3 glass on the sintering temperature and piezoelectric properties of PNN-PZT ceramics were studied. The results indicated that the sintering temperature of PNN-PZT was significantly reduced due to the incorporation of 0.5PbO-0.5B2O3 glass dopant. When the content of 0.5PbO-0.5B2O3 glass was 0.5 wt.%, the sintering temperature of PNN-PZT was observed to reduce from above 1200°C to 920°C while the samples maintained high density (7.91 g/cm3), excellent piezoelectric constant (d33 = 479 pC/N), large electromechanical coupling coefficient (Kp = 0.55), and relatively low electromechanical quality factor (Qm = 79). Moreover, large dielectric constant (e33T/e0 = 2904) and low dielectric loss (tan δ = 0.0166) were obtained in this work.

Effects of BaWO4 additive on Raman phonon modes and structure–property relationship of Ba(Mg1/3Ta2/3)O3 microwave dielectric ceramics

Ba(Mg1/3Ta2/3)O3–BaWO4 (BMT–BW) microwave dielectric ceramics were synthesized using the conventional solid-state sintering technique. Effects of BW additive on Raman phonon modes and structure–property relationship of BMT ceramics were evaluated. The results show that increasing BW contents affect the crystal structures and dielectric properties of BMT ceramics greatly. The lattice parameters (a, c) gradually decrease with the increasing of W6+ content; the lattice parameter ratio (c/a) and the ordering degree reach a maximum value at x=0.04, and then gradually decrease with W6+ concentration. Studies about Raman spectra show that the peak frequencies of A1g(O) modes near 795cm−1 and Eg(O) modes near 158cm−1 and 430cm−1 reach a maximum value at x=0.04; the peak frequencies of Eg(Ta) modes near 210cm−1 reach a minimum value at x=0.04. The relationship between crystal structures and dielectric properties were finally established with vibration modes as the media.

Ba[Mg&amp;lt;sub&amp;gt;(1-&amp;lt;/sub&amp;gt;&amp;lt;italic&amp;gt;&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;&amp;lt;/italic&amp;gt;&amp;lt;sub&amp;gt;)/3&amp;lt;/sub&amp;gt;Zr&amp;lt;italic&amp;gt;&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;&amp;lt;/italic&amp;gt;Nb&amp;lt;sub&amp;gt;2(1-&amp;lt;/sub&amp;gt;&amp;lt;italic&amp;gt;&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;&amp;lt;/italic&amp;gt;&amp;lt;sub&amp;gt;)/3&amp;lt;/sub&amp;gt;]O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;微波介质陶瓷的红外光谱

Ba[Mg(1- x )/3Zr x Nb2(1- x )/3]O3 (BMZN, x =0, 0.10, 0.15) microwave dielectric ceramics were synthesized at 1520℃ using the conventional solid-state sintering technique. Effect of Zr4+ substitution on crystal structures and dielectric properties of the BMZN ceramics was studied by far-infrared spectroscopy (FIR). The results show that with increasing Zr4+ concentration the IR active modes near 370 cm-1 split and new phonon modes appear; the IR active modes near 410 cm-1 disappear; the frequencies of the IR active modes near 230, 290 and 540 cm-1 shift towards high frequency and the intensities of these modes decrease. Studies about the FIR spectra show that with increasing Zr4+ concentration the crystal structures of the BMZN ceramics transformed from hexagonal to cubic structure. The correlations between dielectric properties and IR modes were established with vibration modes as the media.

Far-infrared reflection study on crystal structures and dielectric properties of Ba(Mg1/3Ta2/3)O3-BaWO4 ceramics

Ba(Mg1/3Ta2/3)O3–BaWO4 (BMT–BW) ceramics were synthesized at 1,490 °C for 3 h using the conventional solid-state sintering technique, with BW contents of 2, 4 and 6 wt%. Crystal structures were elucidated by X-ray diffraction (XRD), and vibration modes were obtained by far-infrared spectroscopy (FIR). Correlations among crystal structures, dielectric properties and phonon modes of the ceramics were evaluated. The results demonstrate that the lattice parameter ratio (c/a) and the ordering degree reach a maximum value at x = 0.04. Studies about the FIR spectra also show that the IR active modes near 230 and 540 cm−1 reach a maximum value at x = 0.04. IR active modes near 360 cm−1 split and new phonon modes appear at x ≥ 0.04, which agrees with the change in the crystal structures as proved in the XRD results. The correlations between dielectric properties and IR phonon modes were established with vibration modes as the media.