In this work, a series of BaTiO3-based ceramic materials, Ba(Al0.5Nb0.5)xTi1-xO3 (x = 0, 0.04, 0.06, 0.08), were synthesized using a standard solid-state reaction technique. X-ray diffraction profiles indicated that the Al+Nb co-doping into BaTiO3 does not change the crystal structure significantly with a doping concentration up to 8 %. The doping ions exist in Al3+ and Nb5+ chemical states, as revealed by X-ray photoelectron spectroscopy. The frequencydependent complex dielectric properties and electric modulus were studied in the temperature range of 100~380 K. A colossal dielectric permittivity (>1.5 × 104) and low dielectric loss (<0.01) were demonstrated at the optimal dopant concentration x = 0.04. The observed dielectric behavior of Ba(Al0.5Nb0.5)xTi1-xO3 ceramics can be attributed to the Universal Dielectric Response. The complex electric modulus spectra indicated the grains exhibited a significant decrease in capacitance and permittivity with increasing co-doping concentration. Our results provide insight into the roles of donor and acceptor co-doping on the properties of BaTiO3-based ceramics, which is important for dielectric and energy storage applications.

The semiconductor and display industries require the development of plasma resistant materials for use in high density plasma etching process equipment. Yttria (Y2O3) is a ceramic material mainly used to ensure good plasma resistance properties, which requires a dense microstructure. In commercial production, a sintering process is applied to reduce the sintering temperature of Y2O3. In this study, the effect of the addition of glass frit to the sintered specimen was examined when manufacturing yttria sintered specimens for semiconductor process equipment parts. The Y2O3 specimen was shaped into a Ø50 mm size and then sintered at 1,600 °C for 1~8 h. The characteristics, X-ray diffraction pattern, densities, contraction rate of the specimen, and swelling of the surface of the Y2O3 specimens were investigated as a function of the sintering time and glass frit addition. The Y2O3 specimen exhibited a density of over 4.9 g/cm3 as the sintering time increased, and the swelling phenomenon characteristics were improved by glass frit, by controlling particle size.

La modified lead zirconate titanate ceramics (Pb0.92La0.08)(Zr0.95Ti0.05)O3 = PLZT-8/95/5 were prepared using the conventional solid state reaction method in order to investigate the complex impedance characteristics of the PLZT-8/95/5 ceramic according to temperature. The complex impedance in the PLZT-8/95/5 ceramic was measured over a temperature range of 30~550 °C at several frequencies. The complex dielectric constant anomaly of the phase transition was observed near TU1 = 179 °C and TU2 = 230 °C. A remarkable diffuse dielectric constant anomalous behaviour of the complex dielectric constant was found between 100 °C and 550 °C. The complex impedance spectra below and above TU1 and TU2 were fitted by the superposition of two Cole-Cole types of impedance relaxations. The fast component in the higher frequency region may be due to ion migration in the bulk, and the slow component in the lower frequency region is interpreted to be the formation and migration of ions at the grain boundary or electrode/crystal interfacial polarization.

This study successfully prepared high-porosity aluminosilicate fibrous porous ceramics through vacuum suction filtration using aluminosilicate fiber as the primary raw material and glass powder as binder, with the appropriate incorporation of glass fiber. The effects of the composition of raw materials and sintering process on the structure and properties of the material were studied. The results show that when the content of glass powder reached 20 wt% and the samples were sintered at the temperature of 1,000 °C, strong bonds were formed between the binder phase and fibers, resulting in a compressive strength of 0.63 MPa. When the sintering temperatures were increased from 1,000 °C to 1,200, the open porosity of the samples decreased from 89.08 % to 82.38 %, while the linear shrinkage increased from 1.13 % to 10.17 %. Meanwhile, during the sintering process, a large amount of cristobalite and mullite were precipitated from the aluminosilicate fibers, which reduced the performance of the aluminosilicate fibers and hindered the comprehensive improvement in sample performance. Based on these conditions, after adding 30 wt% glass fiber and being sintered at 1,000 °C, the sample exhibited higher compressive strength (1.34 MPa), higher open porosity (89.13 %), and lower linear shrinkage (5.26 %). The aluminosilicate fibrous porous ceramic samples exhibited excellent permeability performance due to their high porosity and interconnected three-dimensional pore structures. When the samples were filtered at a flow rate of 150 mL/min, the measured pressure drop and permeability were 0.56 KPa and 0.77 × 10-6 m2 respectively.

This work utilizes the commercial finite element software ABAQUS to investigate the factors influencing the mechanical behavior of tantalum carbide (TaC)-based/graphite fibrous monolithic ceramics (FMCs), such as core/shell volume ratio and fiber orientation. The good compliance between experimental and simulated results demonstrates the suitability of the finite element software ABAQUS for exploring mechanical properties in FMCs. According to the results, it was observed that the bending strength of TaC-based/graphite FMC decreased with the change in fiber orientation from 0° to 90°. The displacement amount in the core/shell volume ratio of 75/25 ( C75S25) sample with a fiber orientation of 90° was maximum (with a value of 0.0524 mm), indicating that crack propagation occurred later. Therefore, the sample exhibited better resistance to failure. Generally, C75S25 specimens started to crack later than the core/shell volume ratio of 65/35 ( C65S35) in both fiber orientations and released more energy during crack initiation. Additionally, when the 0°-fiber-oriented specimen failed, more energy was released than the [90°] sample with the same core/shell volume ratio.

The sintering shrinkage behaviors of low temperature cofired ceramics (LTCC) and resistors were compared using commercial LTCC and thick-film resistor pastes, and factors influencing the camber of cofired resistor/LTCC bi-layers were also investigated. The onset of sintering shrinkage of the resistor occurred earlier than that of LTCC in all resistors, but the end of sintering shrinkage of the resistor occurred earlier or later than that of LTCC depending on the composition of the resistor. The sintering shrinkage end temperature and the sintering shrinkage temperature interval of the resistor increased as the RuO2/glass volume ratio of the resistor increased. The camber of cofired resistor/LTCC bi-layers was obtained using three different methods, all of which showed nearly identical trends. The camber of cofired resistor/LTCC bi-layers was not affected by either the difference in linear shrinkage strain after sintering between LTCC and resistors or the similarity of sintering shrinkage temperature ranges of LTCC and resistors. However, it was strongly affected by the RuO2/glass volume ratio of the resistor. The content of Ag and Pd had no effect on the sintering shrinkage end temperature or sintering shrinkage temperature interval of the resistor, or on the camber of cofired resistor/LTCC bi-layers.

Lead-free perovskite ceramics, which have excellent energy storage capabilities, are attracting attention owing to their high power density and rapid charge-discharge speed. Given that the energy-storage properties of perovskite ceramic capacitors are significantly improved by doping with various elements, modifying their chemical compositions is a fundamental strategy. This study investigated the effect of Zn doping on the microstructure and energy storage performance of potassium sodium niobate (KNN)-based ceramics. Two types of powders and their corresponding ceramics with compositions of (1-x)(K,Na)NbO3-xBi(Ni2/3Ta1/3)O3 (KNN-BNT) and (1-x)(K,Na)NbO3-xBi(Ni1/3Zn1/3Ta1/3) O3 (KNN-BNZT) were prepared via solid-state reactions. The results indicate that Zn doping retards grain growth, resulting in smaller grain sizes in Zn-doped KNN-BNZT than in KNN-BNT ceramics. Moreover, the Zn-doped KNNBNZT ceramics exhibited superior energy storage density and efficiency across all x values. Notably, 0.9KNN-0.1BNZT ceramics demonstrate an energy storage density and efficiency of 0.24 J/cm3 and 96%, respectively. These ceramics also exhibited excellent temperature and frequency stability. This study provides valuable insights into the design of KNNbased ceramic capacitors with enhanced energy storage capabilities through doping strategies.

The effects of La3+ substitution for Sr2+-site on the crystal structure and the dielectric properties of (Ba0.7Sr0.3-3x/2Lax) (Ti0.9Zr0.1)O3 (BSLTZ) (0.005 ≤ x ≤ 0.02) ceramics were investigated. The structural characteristics of the BSLTZ ceramics were quantitatively evaluated using the Rietveld refinement method from X-ray diffraction (XRD) data. For the specimens sintered at 1,550 °C for 6 h, a single phase with a perovskite structure and homogeneous microstructure were observed for the entire range of compositions. With increasing La3+ substitution (x), the unit cell volume decreased because the ionic size of La3+ (1.36 Å) ions is smaller than that of Sr2+ (1.44 Å) ions. With increasing La3+ substitution (x), the tetragonal phase fraction increased due to the A-site cation size mismatch effect. Dielectric constant (εr) increased with the La3+ substitution (x) due to the increase in tetragonality (c/a) and the average B-site bond valence of the ABO3 perovskite. The BSLTZ ceramics showed a higher dielectric loss due to the smaller grain size than that of (Ba0.7Sr0.3)(Ti0.9Zr0.1)O3 ceramics. BSLTZ (x = 0.02) ceramics met the X7R specification proposed by the Electronic Industries Association (EIA).

YSZ (Y2O3-stabilized zirconia)-based ceramics have excellent mechanical properties, such as high strength and wear resistance. In the application, YSZ is utilized in the bead mill, a fine-grinding process. YSZ-based parts, such as the rotor and pin, can be easily damaged by continuous application with high rpm in the bead mill process. In that case, adding WC particles improves the tribological and mechanical properties. YSZ-30 vol.% WC composite ceramics are manufactured via hot pressing under different pressures (10/30/60 MPa). The hot-pressed composite ceramics measure the physical properties, such as porosity and bulk density values. In addition, the phase formation of these composite ceramics is analyzed and discussed with those of physical properties. For the increased applied pressure of hot pressing, the tetragonality of YSZ and the crystallinity of WC are enhanced. The mechanical properties indicate an improved tendency with the increase in the applied pressure of hot pressing.

The effects of Ni2+ substitution for Mg2+-sites on the microwave dielectric properties of (Mg1-xNix)(Ti0.95(Mg1/3 Ta2/3)0.05)O3 (0.01 ≤ x ≤ 0.05) (MNTMT) ceramics were investigated. MNTMT ceramics were prepared by conventional solid-state reaction. When the MgO / TiO2 ratio was changed from 1.00 to 1.02, MgTi2O5 was detected as a secondary phase along with the MgTiO3 main phase in the MNTMT specimens sintered at 1,400 °C for 4h. For the MNTMT specimens with MgO / TiO2 = 1.07 sintered at 1,400 °C for 4h, a single phase of MgTiO3 with an ilmenite structure was obtained from the entire range of compositions. The relative density of all the specimens sintered at 1,400 °C for 4h was higher than 95 %. The quality factor (Qf) of the sintered specimens depended strongly on the degree of covalency of the specimens, and the sintered specimens with x = 0.01 showed the maximum Qf value of 489,400 GHz. The dielectric constant (K) decreased with increasing Ni2+ content because Ni2+ had a lower dielectric polarizability (1.23Å3) than Mg2+ (1.32Å3). As Ni2+ content increased, the temperature coefficient of resonant frequency (TCF) improved, from -55.56 to -21.85 ppm/°C, due to the increase in tolerance factor (t) and the lower dielectric constant (K)

The volatilization of alkali ions in (K,Na)NbO3 (KNN) ceramics was inhibited by doping them with alkaline earth metal ions. In addition, the grain growth behavior changed significantly as the sintering duration (ts) increased. At 1,100 °C, the volatilization of alkali ions in KNN ceramics was more suppressed when doped with alkaline earth metal ions with smaller ionic size. A Ca2+-doped KNN specimen with the least alkali ion volatilization exhibited a microstructure in which grain growth was completely suppressed, even under long-term sintering for ts = 30 h. The grain growth in Sr2+-doped and Ba2+-doped KNN specimens was suppressed until ts = 10 h. However, at ts = 30 h, a heterogeneous microstructure with abnormal grains and small-sized matrix grains was observed. The size and number of abnormal grains and size distribution of matrix grains were considerably different between the Sr2+-doped and Ba2+-doped specimens. This microstructural diversity in KNN ceramics could be explained in terms of the crystal growth driving force required for two-dimensional nucleation, which was directly related to the number of vacancies in the material.

In this study, phase-pure titanium dioxide TiO2 ceramics are sintered using standard high-temperature solid-state reaction technique at different temperatures (1,000, 1,100, 1,200, 1,300, 1,400 oC). The effect of sintering temperature on the densification and impedance properties of TiO2 ceramics is investigated. The bulk density and average grain size increase with the increase of sintering temperature. Impedance spectroscopy analysis (complex impedance Z * and complex modulus M *), performed in a broad frequency range from 100 Hz to 10 MHz, indicates that the TiO2 ceramics are dielectrically heterogeneous, consisting of grains and grain boundaries. The complex impedance Z *-plane indicates the resistance of grains of the TiO2 ceramics increases with increasing sintering temperature, while that of grain boundaries develops in the opposing direction. The complex modulus M *-plane shows a grain capacitance that seems to be independent of the sintering temperature, while that of the grain boundaries decreases with increasing sintering temperature. These results suggest that different sintering temperatures have effects on the microstructure, leading to changes in the impedance properties of TiO2 ceramics.

Porous mullite-corundum ceramics were prepared using organic foam impregnation method with alumina and silica as raw materials. The influence of alkaline treatment and surfactant modification on polyurethane foam were studied. Effects of sintering process and material composition on porous mullite-corundum ceramics were investigated. The results show that the hang-pulp quantity of polyurethane foam increases with alkaline treatment. After treatment with 3 wt% SDS solution, the hang-pulp quantity of polyurethane foam further improved. Open porosity of sample decreased with elevation of sintering temperature and holding time, and compressive strength of sample showed a trend opposite to the change of porosity. The open porosity of the sample was enhanced by the increase of m(Al2O3/SiO2); the compressive strength decreased with increase of m(Al2O3/SiO2). However, when m(Al2O3/SiO2) was 2.5, the compressive strength of the sample reached 6.23 MPa, and the open porosity of the sample was 80.7 %.

본 논문은 17~19세기 명․청대 박고문자기의 제작배경, 유형과 시기별 특징, 그리고 조 선과 일본도자에 미친 영향관계에 대한 전반적인 고찰을 목적으로 삼았다. 박고문자기는 고동기에 대한 완상 및 애호가 일종의 문인취미로서 확산되었던 명․청대 사회상을 반영한 대표적인 시각작품이다. 그 제작배경과 관련하여 당대 문헌사료들을 통해 박고취미가 성행했던 시대적 배경을 확인하였다. 이어서 17~19세기 자기 박고문에서 보이 는 고기물 도상, 문방청완, 팔보 등 기타 길상소재 등의 구성요소로 유형 분류를 시도하고, 유형별 자기 박고문의 편년자료와 양식을 통해 17~19세기 박고문자기의 시기별 특징을 살펴 보았다. 그 결과, 17~19세기 자기 박고문은 크게 4가지 유형으로 분류가 가능했으며, 이는 곧 시기별 박고문자기의 변천과 특징으로 이어졌다. 17세기 중후반, 경덕진 민요에서 문인취 향이 적극 반영되어 나타난 박고문자기는 18세기 이후에는 官樣의 내수뿐 아니라 다양한 품종으로 유럽 수출자기로도 크게 성행하였다. 19세기에는 전반적으로 자기의 질이 쇠퇴되며, 민간 잡보를 비롯한 여러 길상적 문양요소로 이전보다 더욱 번잡해지는 구성으로 변모되었다. 한편 박고문자기는 같은 한자 문화권이었던 조선과 일본도자에도 영향을 미쳤으며, 현전 하는 작품들의 비교 분석을 통해 그 영향관계를 확인하였다. 조선의 경우, 조선 후기 골동애 완풍조 등 중국의 복고적 취향을 잇는 주요 매개체로 작용하였으며, 이와 동일한 맥락에서 19세기 민화적 요소와 결합되어 자기의 문양으로 변용되었다. 일본은 조선과는 달리 17~18세기 유럽시장을 배경으로 한 수출자기에서의 수용과 변용이 이뤄졌으며, 일본식 미 감이 가미된 일본 수출자기의 특색으로 자리하였다. 이처럼 조선과 일본 각국에서 중국 박고 문자기를 수용하는 시기와 경로, 모방과 변용양상이 다르게 나타난 점을 통해 동아시아 도자 문화에서 갖는 박고문자기의 의미를 확인할 수 있었다.

NbC, HfC, TaC, and their solid solution ceramics have been identified as the best materials for ultrahigh-temperature ceramics. However, their structural stability and elastic properties are mostly unclear. Thus, we investigated structure and elastic properties of (Nb1-xTax)C and (Nb1-xHfx)C solid solutions via ab initio calculations. Our calculated results show that the stability of (Nb1-xTax)C and (Nb1-xHfx)C increases with the increase of Hf and Ta content, and (Nb1-xHfx)C is more stable than (Nb1-xTax)C at the same content of Hf and Ta. The lattice constants decrease with increasing of Hf and Ta content. (Nb1-xTax)C and (Nb1-xHfx)C carbides are mechanically stable and brittle. Bulk modulus of (Nb1-xTax)C increases with increasing Ta content. In contrast, bulk modulus of (Nb1-xHfx)C decreases with increasing Hf content. Hardness of solid solutions shows the highest values at the (Nb0.25Ta0.75)C and (Nb0.75Hf0.25)C. In particular, (Nb0.75Hf0.25)C shows the highest hardness for the current system. The results indicate that the overall mechanical properties of (Nb1-xHfx)C solid solutions are superior to those of (Nb1-xTax)C solid solutions. Therefore, controlling the Hf and Ta element and content of the (Nb1-xTax)C and (Nb1-xHfx)C Solid solution is crucial for optimizing the material properties.

SiAlON-based ceramics are a type of oxynitride ceramics, which can be used as cutting tools for heatresistant super alloys (HRSAs). These ceramics are derived from Si3N4 ceramics. SiAlON can be densified using gaspressure reactive sintering from mixtures of oxides and nitrides. In this study, we prepare an α-/β-SiAlON ceramic composite with a composition of Yb0.03Y0.10Si10.6Al1.4O1.0N15.0. The structure and mechanical/thermal properties of the densified SiAlON specimen are characterized and compared with those of a commercial SiAlON cutting tool. By observing the crystallographic structures and microstructures, the constituent phases of each SiAlON ceramic, such as α- SiAlON, β-SiAlON, and intergranular phases, are identified. By evaluating the mechanical and thermal properties, the contribution of the constituent phases to these properties is discussed as well.

Zirconia has excellent mechanical properties, such as high fracture toughness, wear resistance, and flexural strength, which make it a candidate for application in bead mills as milling media as well as a variety of components. In addition, enhanced mechanical properties can be attained by adding oxide or non-oxide dispersing particles to zirconia ceramics. In this study, the densification and mechanical properties of YSZ-TiC ceramic composites with different TiC contents and sintering temperatures are investigated. YSZ - x vol.% TiC (x=10, 20, 30) system is selected as compositions of interest. The mixed powders are sintered using hot pressing (HP) at different temperatures of 1300, 1400, and 1500oC. The densification behavior and mechanical properties of sintered ceramics, such as hardness and fracture toughness, are examined.

이 글에서는 신안해저문화재 가운데 자기 고족배(高足杯)에 주목하여 출수 현황과 조형 특징을 정리하고, 중국 내 생산 및 소비 유적 출토품과 비교를 통해 그 성격과 특징을 살펴 보았다. 필자가 지금까지 파악한 바로는 신안선에서 고족배가 60 여점 발견되었는데 이는 전체 도자기 수량의 0.3% 미만을 차지하는 매우 적은 수량이다. 그러나 청자와 백자가 모두 확인되며 특히 일부 백자 고족배의 경우 부량자국이 관할한 우수한 민간 요장에서 생산된 고 급 생산품이기에 일부는 특별한 목적성을 갖고 교역된 기종으로 여겨진다. 즉 일부 고족배는 높은 위상을 가진 고급 무역품으로 당시 중국 민간 요장에서 중앙으로 공납했던 양식과 유사하다는 점에 주목할 필요가 있다. 즉 원나라 관에 공납․유통되었던 것 과 유사한 양식을 갖춘 것이 무역에서 통제 대상이 아니라 오히려 고급 상품성을 가지고 지 역적․계층적으로 폭넓게 유통되었음을 확인한 셈이다. 따라서 신안선에서 발견된 고족배 분석으로 원대 도자무역의 개방된 성격을 확인할 수 있다. 한편 각종 회화와 문헌 자료를 통해 고족배의 용례에 대해 살펴본 결과 중국에서 술잔 혹 은 찻잔, 공양구로로 사용되었음을 확인하였다. 일본에서는 신안선에서 발견된 고족배의 비율을 반영하듯 소비지역에서 출토사례가 많지는 않았다. 그러나 그러한 가운데에도 일부 선 종 사찰에서 고족배가 출토되었다는 점은 소비지 성격을 이해하는데 참고자료로 도움이 된 다. 일본의 용례를 살펴본 결과 술잔, 과일이나 음식 등을 바치는 공양기로 사용되었을 가능 성이 가장 높았으며, 오랫동안 전세되어 내려오면서 그 용도가 바뀌어 다실에서 향로로 사용 되기도 하였다. 또 에도시대 중국 청자 고족배가 재현 대상이 되었던 사례를 확인하여, 일본 일부에서는 중국 고족배를 분명하게 인식하고 있었고 또 소장 대상으로서 애호했음을 알 수 있었다.

광채는 태생부터가 유럽시장의 수요에 부응하기 위해 생산된 자기이지만, 18세기 후반 이후 이슬람 세계로의 소비정황이 확인되고, 19세기에 이르면 본격적인 이슬람 시장으로의 수출이 이루어져 광채자기의 생산과 수출과정에 모종의 변화가 있었음을 짐작해 볼 수 있다. 18세기의 대표적 예로 무굴제국에 유입된 광채 식기세트가 있으나 소량에 불과하다. 이 는 아마도 당시 동인도회사가 중서무역에 절대적 우위를 선점하는 가운데, 영국 동인도회사 령의 무굴제국에서 아시아 간 역내무역 형태로 소량 주문되어 유입된 것으로 판단된다. 당시 아시아 역내무역의 주요 축이었던 인도 무굴제국과 중국과의 소규모 거래에 의한 것으로, 수 출된 광채자기의 장식이 유럽 도기에서 주로 사용된 ‘백색 위의 백색(Bianco Sopra Bianco)’ 기법이 상용된 것으로 보아 특정 계층을 위한 소량의 주문품으로 보인다. 다만 이 때 광주의 요업계 역시 동인도회사를 통한 유럽으로의 대규모의 수출에 집중되었기 때문에, 이슬람 세계는 핵심 시장이 아니었다. 그러다가 1840년대 광동의 일항 체제가 종식되면서, 광채의 수출에도 드디어 변화가 감지된다. 19세기의 중국 요업계는 주요 고객을 잃으면서 새로운 시장으로의 개척이 필요했 고, 광채 생산업계는 때마침 1840년대 난징조약에 의한 對중국의 자유무역이 활발해지면서 페르시아 카자르 왕조․이집트․오스만 제국 등 이슬람 세계에 의한 직접적 주문과 함께 이 슬람 세계로의 본격적 수출이 이루어 진 것으로 판단된다. 이슬람 세계로 적지 않은 수량이 수출되면서, 카자르 왕조에서 생산된 채회도기의 다수가 광채 양식을 그대로 답습하기도 하 였다. 즉 당시 이슬람 세계에서의 광채 수입은 상당한 수준에 이르렀음을 확인할 수 있다.

This paper focuses on the electrical properties and stability against DC accelerated aging stress of ZnO-V2O5-MnO2- Nb2O5-Bi2O3-Co3O4-Dy2O3 (ZVMNBCD) varistor ceramics sintered at 850 - 925 ℃. With the increase of sintering temperature, the average grain size increases from 4.4 to 11.8 mm, and the density of the sintered pellets decreases from 5.53 to 5.40 g/ cm3 due to the volatility of V2O5, which has a low melting point. The breakdown field abruptly decreases from 8016 to 1,715 V/cm with the increase of the sintering temperature. The maximum non-ohmic coefficient (59) is obtained when the sample is sintered at 875 ℃. The samples sintered at below 900 oC exhibit a relatively low leakage current, less than 60 mA/cm2. The apparent dielectric constant increases due to the increase of the average grain size with the increase of the sintering temperature. The change tendency of dissipation factor at 1 kHz according to the sintering temperature coincides with the tendency of the leakage current. In terms of stability, the samples sintered at 900 ℃ exhibit both high non-ohmic coefficient (45) and excellent stability, 0.8% in ΔEB/EB and -0.7% in Δα/α after application of DC accelerated aging stress (0.85 EB/85 oC/24 h).