Two-phase composite ceramics consisting of 8mol% Y2O3 stabilized ZrO2 and 10 to 70wt% of ZrSiO4 were fabricated. The ceramics showed ionic conduction above 500°C. The conductivity of the ceramics decreased with increasing ZrSiO4 content, but the ceramics with 70wt% of ZrSiO4 still had a high conductivity of 3×10-1S·m-1 at 1000°C. The activation energy of conductivity of the ceramics was 104kJ·mol-1, which agreed closely with that of a pure 8mol% Y2O3 stabilized ZrO2. The thermal expansion coefficient of the ceramics decreased with increasing ZrSiO4 content, and the ceramics with 70wt% of ZrSiO4 showed a low average linear thermal expansion coefficient of 5.5×10-6°C-1 between room temperature and 1000°C. The 8mol% Y2O3 stabilized ZrO2-ZrSiO4 ceramics showed higher ionic conductivity than the conventional 8mol% Y2O3 stabilized ZrO2-Al2O3 ceramics, when they have the same thermal expansion coefficients.
Abstract At the surface of the tin-plated brass substrate placed at 50°C, the tin whiskers grew evidently within a short time, due to the formation of zinc oxide on the surface and alloying between plated tin and brass substrate as supposed. While at the surface of the brass substrate plated with tin on nickel, there was no trace of the tin whisker at all. Nickel greatly represses the diffusion of base metal materials into the tin layer. Nickel and tin plated monolithic chip capacitors placed at the same condition for 18 years were also observed and the tin whisker growth phenomenon has never taken place either. As a result, the tin plated film on the nickel over silver thick film does not provide the tin whisker growth. Nickel underplating plays an important role in tin plated capacitors for not only the solder leaching but also the tin whisker growth problems.
Third-harmonic-wave distortion (THD) of high-K ceramic multilayer capacitors is usually as high as -60 dB due to the nonlinear behavior of ferroelectric BaTiO/sub 3/-based materials. A recently developed SrTiO/sub 3/-based material makes possible a multilayer capacitor with less wave distortion. THDs of better than -90 dB have been obtained over a wide range of applied AC voltages. This dielectric has a dielectric constant of 1300 and is fired at 1140 degrees C. Performance data and specific applications are reported.< >
Temperature dependences of piezoelectric properties were studied for (001) textured ceramics of bismuth layer-structured ferroelectrics, SrBi 2 Nb 2 O 9 (SBN). The textured ceramics with varied orientation degrees were fabricated by templated, grain-growth method, and the temperature dependences of resonance frequency were estimated. Excellent temperature stability of resonance frequency was obtained for the 76% textured ceramics. The resonance frequency of the 76% textured specimens varied almost linearly over a wide temperature range. Therefore, the variation was slight, even in a high temperature region above 150degC. Temperature stability of a quartz crystal oscillator is generally higher than that of a ceramic resonator around room temperature. The variation of resonance frequency for the 76% textured SrBi 2 Nb 2 O 9 was larger than that of oscillation frequency for a typical quartz oscillator below 150degC also in this study. However, the variation of the textured SrBi 2 Nb 2 O 9 was smaller than that of the quartz oscillator over a wide temperature range from -50 to 250degC. Therefore, textured SrBi 2 Nb 2 O 9 ceramics is a major candidate material for the resonators used within a wide temperature range.
In order to make the monolithic ceramic capacitors with a base metal internal electrode, the ceramics of {(Ba 1- x Ca x )O} m {(Ti 1- y Zr y )O 2 } compositions were investigaed, where 0.02≦ x ≦0.22, 0< y ≦0.20 and 1.005≦ m ≦1.030. These ceramic materials are sintered in an atmosphere of low oxygen to yield a high resistivity (10 12 Ω-cm), a high dielectric constant (7,000∼9,000), and a low dissipation factor of less than 2.5%. The monolithic capacitors of these ceramics with nickel electrode are as reliable as those with precious metal electode.
