Key Engineering Materials Vols. 336-338

Abstract: LTCC technology offers low temperature firing (<900 °C) of a materials system, which is based on LTCC sheets/tapes and (ideally) compatible thick-film components. Screen-printed materials on LTCC tapes, such as conductor, resistor, inductor thick-films are co-fired (simultaneously fired), providing a highly-functional package. This comes along with additional benefits such as ease of LTCC tape structuring, fabrication of hermetic and complex 3-D structures, etc. The major difficulty encountered arises from the differential shrinkage rate of LTCC tape and thick-film components, which has to be avoided for fabrication of warpage-free, flat surfaces that is vital for membranes, beams, etc. Therefore the goal of this study is the reduction of deformation, by matching the shrinkage rate of conductor with that of LTCC, which is achieved by mixing the commercially-available paste with selected additives.

Abstract: A simple laboratory technique for the routine preparation of antimony-doped tin oxide (ATO) on float glass substrates (25×76×1mm3) was described. The process employed sol-gel dip-coating approach in the absolute ethanol solution of metal salts of tin (II) chloride dehydrate and antimony trichloride. Microstructural and morphological analyses of as-prepared films were performed at different conditions. With increase of annealing temperature from 400 to 550°C, the evolution of grain size and the morphologies of ATO films were analyzed by means of atom force microscopy (AFM). The studies on the morphological development suggested that higher annealing temperature led to a decrease in the surface roughness of the deposited films. The XRD patterns revealed that as-prepared ATO films were in the crystallization of a tetragonal rutile structure of SnO2 with highly (110) preferred orientation.

Abstract: Antimony-doped tin oxide (ATO) transparent conducting thin films were prepared by sol-gel dip-coating technique in the alcohol solution of metal salts of tin (II) chloride dehydrate and antimony tri-chloride. Usual glass slides (25×76×1mm3) were used as the substrates. As-prepared thin films were dried at temperature of 343K and annealed at temperatures of 673~823K. Their optical properties were analyzed by Hitachi U-3310 spectrophotometer. The good optical transmission of the ATO thin films has been obtained as high as 80%-90% in visible region by the optimization of deposition conditions, but decreased substantially in IR region. From the X-ray diffraction (XRD) measurements, it showed that ATO films had the similar structures with the pure tin oxide films, i.e. tetragonal rutile structure, despite of some rhombic SnO crystals. We analyzed the transmittance in the visible region depending on the vary Sb doped level, temperature, and dip-coating times. The sheet resistance of the investigated thin films was determined by four-probe method, showing that it was about 85-1009/□, which decreased with the increase of antimony doped concentration.

Abstract: CuIn1-xGaxSe2(CIGS) precursor films are fabricated on Mo foil by coelectrodeposition. The influence of the applied potential and the electrolyte additive in the process of electrodeposition are discussed. The precursor films are annealed in Ar for a short time to synthesize the polycrystalline thin film. The annealed layers are only phase-pure CuIn0.7Ga0.3Se2 and show a good crystallinity.

Abstract: Indium oxide (In2O3) films was deposited on TiN substrates by the metal organic chemical vapor deposition technique using a triethylindium and oxygen mixture. The films deposited at 250-350°C were polycrystalline, while that deposited at 200°C was close to amorphous. XRD and SEM analyses indicated that the films grown at 350°C had grained structures with the (222) preferred orientation.

Abstract: Samples of La(TixMn1-x)O3 (0.1 ≤ x ≤ 0.7) were sintered at different temperatures. The experimental results showed that the resistivity-temperature curves of the samples match NTC characteristic. The crystal structure was analyzed using X-ray diffraction and the microstructure was observed by scanning electron microscope.

Abstract: In this study, shrinkage behavior and coefficient of thermal expansion (CTE) of novel nickel (Ni) powder with an addition of dielectric material, BaTiO3, have been investigated to reduce the large shrinkage mismatch between Ni electrode and dielectric material and to control the thermal and/or residual stresses created by CTE mismatch in MLCCs (multilayer ceramic capacitors). For which two kinds of Ni powders were used. The component of Ni powders is analyzed by XRF, and the thermal behavior is measured by TG/DTA. The Ni and BaTiO3 powders were mixed with 9:1, 8:2, and 7:3 volume ratios. The BaTiO3-added Ni green bodies were fabricated through cold isostatic pressing, and then sintered to 1300°C in a reduction atmosphere. The shrinkage behavior with volume ratio was checked during sintering from 700 to 1300°C with 300°C interval. The CTE was measured in inert (argon) atmosphere with sintered samples. It is found that the shrinkage behavior and the CTE of Ni electrode are dependent on the volume of BaTiO3 added. The particle size of Ni powder also affects the microstructure and its sintering density, with less effect of its component.

Abstract: Constantan thin film was deposited on Al2O3 substrate by vacuum evaporation technology and semiconductor ordinary photolithography to form the sensitive bar of strain-resistance pressure sensor. The static characteristics of the resultant ceramic sensor were measured and the results showed that the linearity, repetition properties, return error and the creep of the ceramics pressure sensor are more excellent than the conventional sensor.

Abstract: Sr0.48Ba0.24Ca0.28TiO3-based varistor ceramics with an excellent capacitor-varistor multifunctional characteristics (V1mA = 11 ~ 49 ν.mm-1, α = 6.1 ~ 11.3, ε r max=3.5×105, tanδmin = 5%) were prepared using conventional solid method. The effect of oxidation temperature and time on structure and electrical properties were investigated. The results show that with increasing the oxidation temperature from 800°C to 900°C, the varistor voltage V1mA and non-linearity coefficient α defining varistor characteristics increase linearly, while the dielectric constant ε r and dielectric loss tanδ decrease linearly. There exists an optimum α value when the specimens were oxidized at 850°C for 3h. This behavior was explained through various defect reactions of dopants.