Papers by Keyword: Low Temperature Sintering

Abstract: The sintering behavior and microwave dielectric properties of the (Ca0.9375Sr0.0625)0.25(Li0.5Sm0.5)0.75TiO3 (CSLST) ceramics doped with different amounts of Li2O-B2O3-SiO2-CaO-Al2O3 (LBSCA) glass were investigated. The sintering temperature of the CSLST ceramics can be effectively reduced over 200oC due to the addition of LBSCA glass. For the 5 wt% LBSCA-doped CSLST ceramics, which are sintered at only 1000 oC for 5 h, show optimum microwave dielectric properties as follows: εr=84.74, Qf=2446 GHz and τf=-12.48 ppm/oC.

Abstract: Crystal structure and microwave dielectric properties of (Ca1-xSmx) [(Li1/3Nb2/3)0.95Zr0.15]3+δ(0.0≤x≤0.2,CSLNZ) ceramics were investigated. A single phase with orthorhombic perovskite structure was obtained at x=0.0~0.08. With an increase of Sm3+ content, the quality factor value firstly increased, and then began to decrease at x=0.03 due to a decrease of the degree of B-site 1:2 ordering. The variation of τf with tolerance factor was discussed. When x=0.05, the optimum microwave dielectric properties: the permittivity is 32.4，the quality factor is 16560GHz，and the temperature coefficient of resonator frequency is −6.3×10−6/°C。

Abstract: Crystal structure and microwave dielectric properties of Ca[(Li1/3Nb2/3) 0.92Zr0.08]O3−δ−xTiO2(0≤x≤0.2) ceramics were investigated. A single phase with orthorhombic perovskite structure was obtained at x=0.0~0.1. With an increasing of Ti4+ content, the Qf value decreased due to a decrease of the degree of B-site 1:2 ordering. However, the τf value firstly increased from-14.2ppm /°C to -6.6ppm/°C, and then moved to the negative direction. When x=0.05, the optimum microwave dielectric properties: εr=32.8, Qf =19460GHz and τf =−8.3 ppm/°C.

Abstract: CaO-B2O3-SiO2 glass ceramics were prepared by powders of different particle sizes. The relationship between CBS powder characteristics and structures was studied by XRD and SEM, and the effect of powder characteristics on sintering properties, dielectric properties at 10GHz, thermal properties (CTE) were investigated to obtain low-temperature sintered glass ceramics. The results showed that the median particle size of glass powders reduced, sintered temperature and apparent porosity decreased. But at the same time, bulk density and thermal expansivity increased. The sample with the powders of D50=2.34μm could be sintered at 850 with the density about 2.615g•cm-3 and the water absorption about 0.16%. Having a dielectric constant of 6.16 and a dielectric loss of 1.9×10-3 at 9.98GHz, the sintered sample could satisfy the requirements of the substrate materials used in LTCC in some fields.

Abstract: As by-product of steeling making, steel slag accounts for 10% to 13% of steel production. Utilization of it as resource has been tried in many fields. For example, it can be used as building materials, most for paving and backfilling. However, utilization level of steel slag is still low, and to find a novel way to utilize steel slag efficiently is urgent. Steel slag includes much calcium and silicon, similar to those of clay, which means that it can be one of the raw materials for ceramic sintering. In this research, the process of steel-slag based ceramics sintering was developed. The ceramic tiles with excellent performance were obtained, with up to 36% steel slag added. By EPMA, the possible crystal phases that exist in the ceramic samples have been discussed. By XRD analysis, the main crystal phases of steel slag ceramics were identified, which are anorthite, α-quartz and magnetite. The clinoenstatite can be obtained through increasing the proportion of steel slag in the formula. The diopside can be obtained if the talc was added. These are key factors to obtain excellent performance ceramic tiles under low sintering temperature.

Abstract: Various fluorides (3 - 8 wt%) were added to a La9.33Si6O26 (LSO) powder synthesized by calcining the corresponding oxides mixture at 1100°C for 4 h. The addition of BaF2, AlF3 or Ba3Al2F12 caused an appreciable and substantial increase in bulk density after sintering at 1400º and 1450°C, respectively. These fluorides melt below 1400°C to form liquid phase which could assist the densification at low temperatures. Abnormal grain growth was observed for LSO samples with the addition of AlF3 and Ba3Al2F12, but it was effectively suppressed by stepwise sintering at 1400º and 1450°C. The BaF2 addition brought about the simultaneous promotion of densification and moderate grain growth, leading to the production of a densified LSO sample showing a conductivity of 1.5 x 10–2 Scm–1 at 800°C with an activation energy of 1.23 eV.

Abstract: Ferro-materials which possess both capacitance and inductance were sintered at low temperature using Bi2O3 as sintering additives. The composition of ferro-materials is 0.4PMZNT- 0.6NiCuZn. PMZNT relaxor ferroelectric is a solid solution that consists of Pb(Mg1/3Nb2/3)O3, Pb(Zn1/3Nb2/3)O3 and PbTiO3. NiCuZn ferrite with general formula is Ni0.2Cu0.2Zn0.6Fe2O4. Effects of the content of Bi2O3 and sintering temperature on the relative density of prepared ferro-materials have been studied. Dense ferro-materials were obtained at as low as 890°C with 2.0 wt% of Bi2O3. The X-ray diffractometer (XRD) identifications showed that ferro-materials consisted of distinct ferroelectric and ferromagnetic phases. Scanning electron microscopy (SEM) observations revealed that low temperature sintered ferro-materials possess high density and fine-grained microstructures. Prepared ferro-materials exhibit electromagnetic properties.

Abstract: Microwave dielectric ceramics with low sintering temperature were obtained by sol-coating method. The effect of glass additives on the sintering temperature and microwave dielectric properties of BaO–Nd2O3–TiO2 ceramics were investigated. The ceramics added with NBS glass have much higher quality factor Qf= 4658.9 GHz. The ceramics added with BBS glass have the highest dielectric constantεr=71.4 and lest temperature coefficient of resonant frequency τf =29.15×10-6/ °C. The ceramics added BBS glass are as follows:εr=58.58, Qf= 2986GHz, τf =29.15×10-6/ °C sintered at 1060°C where the ceramics can be co-fired with copper electrode.

Abstract: Willemite ceramics (Zn2SiO4) possess excellent millimeter-wave dielectric properties, but it also has a high sintering temperature above 1300°C by traditional solid-state reaction and relatively large negative τf value. Zn2SiO4 nanoparticles synthesized by Sol–Gel method were used to improve the sintering and dielectric properties of the Zn2SiO4 ceramics. Using the nanoparticles, Zn2SiO4 ceramics can be sintered at a low temperature, 1150°C and exhibited improved microwave dielectric properties of εr =6.62, Q × f=24500 GHz, τf =-59ppm/°C. By adding TiO2 with high positive τf value (+450 ppm/°C) and CuO as sintering aid, near zero τf value and low sintering temperature can be achieved. With 11wt% of TiO2 and 5 wt% of CuO, an εr value of 9.3, a Q × f value of 12200GHz and a τf value of -11 ppm/°C were obtained at 1000°C, confirming the promising potential of the CuO-added TiO2-Zn2SiO4 ceramics as candidate materials for low–temperature cofired ceramic (LTCC) devices.

Abstract: For the transmutation of the very long half-lived isotopes which are separated from the spent nuclear fuels, it is necessary to find proper inert matrices these are stable under heavy neutron irradiation at high temperature. Silicon nitride ceramics is a candidate since it is very tolerant for heavy neutron irradiation and keeps relatively high thermal conductivity. For these reasons, we try to sinter Si3N4 ceramics containing large amounts of CeO2 as a simulant for Am2O3, a typical transuranium element. The low-temperature pressureless-sintering behavior of the ceramics and chemical and thermal properties of the obtained sintered bodies are reported.