The dielectric property and thermal expansion property of Bi 2 O 3 -ZnO-Nb 2 O 3 -based (BZN) ceramics filler reinforced composites have been investigated as a function of temperature range from −50 to 175°C. The composites with adjustable temperature coefficient of frequency (τ f ) and dielectric temperature coefficient (a " ) are achieved by filling the ceramic filler with different a " into polymer matrix. A series of polytetrafluoroethylene (PTFE) based composites blended with different amount of ceramic filler with different a " have been studied in this paper. The results indicated that with the amount of ceramic filler increasing, both of the relative permittivity and dissipation factor of composites increased. Composite filled with positive a " (245 ppm/°C) BZN ceramic filler (40 vol.%) has low a " (22 ppm/°C), while filled with near-zero a " (10 ppm/°C) BZN ceramic filler (40 vol.%) have low τ f (−5 ppm/°C).Keywords Composite . Dielectric property . Thermal expansion property . Temperature compensationWith the development of electronic information technology, the miniaturization and high-speed operation have become the predominant trend for electronic components, which requires the microwave dielectric materials with reasonable relative permittivity, low dissipation factor, good frequency and temperature stability in a wide spectrum range, and good mechanical and thermal stability [1,2]. In these properties, temperature coefficient of frequency (τ f ) has received intensive attention for reducing temperatureinduced drift. The τ f depends both on the coefficient of thermal expansion (CTE) and the dielectric constant of temperature coefficient (a " ) [3-5]. However, polymer, widely used in packaging and substrates, has the main disadvantages of its high linear CTE and large negative a " . A mechanism for the temperature compensation of τ f in polymer composites has been obtained by introducing ceramic filler with a different a " into polymer matrix [3]. For efficient filling of polymers by ceramics filler with different dielectric properties, high dielectric constant microwave composites with near-zero τ f can be achieved and it would be an effective way to reduce CTE and a " [6].In this paper, high dielectric constant microwave composites with adjustable τ f are achieved by introducing two ceramic fillers with different a " into polymer matrix, one with a positive a " and the other with near-zero a " to match the negative a " of polymer. Polytetrafluoroethylene (PTFE) is selected as the polymer matrix. Bismuth-based pyrochlore dielectric ceramics (BZN) is selected as the ceramic filler. Due to its excellent dielectric and chemical properties, PTFE has been extensively applied to microwave devices. Bismuth-based pyrochlore dielectric ceramics (BZN) have attracted attention in microwave dielectric areas because of their low sintering temperature, high relative permittivity, and wide adjustable a " range [7]. BZN/PTFE microwave composites were prepared by using the filler processing technology. The effect of...

Purpose: Compared relative translucency of IPS e.max CAD,Vita Suprinity,Lava Zirconia,Cercon Zirconia,Zenostar and upcera Zirconia, to provide a reference for the clinical aesthetic choice. Method: Relative translucency were calculated from the luminous reflectance (Y) of the specimens with a black (Yb) and a white backing (Yw) to give Yb/Yw with Minolta CR-321.One-way analysis of variance and Tukey’s multiple comparison test were used to analyze the data (P<0.05). Results: Relative translucency of control group was 0.577-0.843,while experimental group was from 0.798(IPS e.max CAD) to 0.947(upcera Zirconia),there were significantly different between the groups. The relative translucency of the six systems are as follows: IPS e.max CAD >Vita Suprinity >Lava Zirconia >Cercon Zirconia >Zenostar >upcera Zirconia. Conclusion: There were significantly different between the six groups, for patients with anterior tooth areas restoration and high aesthetic requirements, IPS e.max CAD and Vita Suprinity are recommended; For patients with poor transmittance of adjacent teeth, and the abutments are dark which need to be covered can choose Lava Zirconia and Cercon Zirconia; For low transparency like posterior areas and severe tetracycline teeth, upcera Zirconia and Zenostar ceramic blocks may be considered.