Te-Yi Chen

Deposition of preferred-orientation ZnO films on the ceramic substrates and its application for surface acoustic wave filters

Polycrystal ZnO films with c-axis (002) orientation have been successfully grown on the lead-based ceramic substrates by rf magnetron sputtering technique. The deposited films were characterized as a function argon-oxygen gas flow ratio and rf power. Crystalline structures of the films were investigated by x-ray diffraction, scanning electron microscopy, and atomic force microscopy. Highly oriented films with c-axis normal to the substrates can be obtained by depositing under a total pressure of 10 mTorr containing 50% argon and 50% oxygen and rf power of 70 W. The phase velocity, electromechanical coupling coefficient, and temperature coefficient of frequency of surface acoustic wave (SAW) device with ZnO/IDT/PT (IDT: interdigital transducer; PT:PbTiO3 ceramics) structure were investigated. It shows that the preferred oriented ZnO film is beneficial for improving the electromechanical coupling coefficient of SAW device.

Fabrication of modified lead titanate piezoceramics with zero temperature coefficient and its application on SAW devices

The Samarium-modified, lead titanate ceramics with a composition of (Pb0.67Ca0.15Sr0.06Sm0.08) (Ti0.98Mn0.02)O3 were prepared by conventional mixed-oxide method. By properly varying the sintering and poling conditions, the samples with zero temperature coefficient of resonant frequency were fabricated. The piezoelectric and dielectric properties were measured; it showed that the samples with zero temperature coefficient still keep high-thickness, electromechanical coupling coefficient, kt (>0.55), and small planar electromechanical coupling coefficient, kp. Surface acoustic wave (SAW) filters were fabricated; and the properties, including phase velocity and electromechanical coupling coefficient, were measured. Microstructural and compositional analyses have been carried out using scanning electron microscopy and x-ray diffraction.

Effects of Sintering Temperature on the Dielectric and Piezoelectric Properties of Nb-Doped PZT Ceramics and Their Applications

The PZT-based ceramics with a composition of Pb1 − 0.5x (Zr0.52Ti0.48)1 − x Nb x O3; x = 0.04–0.06 were prepared by conventional mixed-oxide method, with sintering temperature at 1200°–1300° for 2 hours. Microstructural and compositional analyses of the PZT-based ceramics have been carried out using XRD and SEM. The dielectric constant measured at 1 kHz is about 1500 and the loss factor is small than 2%. The maximum planar electromechanical coupling coefficient, k p , is 0.59. It showed that the Nb additives were helpful improve both of the dielectric and piezoelectric properties. Surface acoustic wave (SAW) filters were fabricated and the property, phase velocity, were measured.

Grain boundary scattering for temperature coefficient of resistance (TCR) behaviour of Ta-Si-N thin films

In this study, we have investigated the electrical properties of TaxSiyNz thin films deposited by reactive co-sputtering at different nitrogen flow ratios. The electrical resistivity and temperature coefficient of resistance (TCR) were measured by an I?V measurement system including the four-point probe from 30 to 100??C. The results indicated that the electrical resistivity decreased with increasing temperature, i.e. negative TCR, in each film prepared at different N2 flow ratios. The phase formation of a Ta?Si?N film at different N2 flow ratios (5?30%), as well as the change in microstructure from a symmetric broad peak to an asymmetric peak, was studied by a grazing incident x-ray diffractometer. In view of the fact that the grain size increases with increasing N2 flow ratio, it would be expected that increasing resistivity and magnitude of negative TCR with increasing grain size nature may be due to scattering of electrons by the grain boundaries. It is probable that coarse grained material of Ta?Si?N with amorphous-like microstructure has a higher electrical resistivity due to the high ratio of the grain boundary area and increase in non-metallic amorphous SiNx. The electrical properties of these films are also discussed by the grain boundary scattering model.

Strontium doping effects on the characteristics of Sm-modified PbTiO3 ceramics

Abstract In this paper, Sr dopants are introduced in the Sm-modified lead titanate (PbTiO 3 ) ceramic systems with a composition of (Pb 0.88− x Sr x Sm 0.08 )(Ti 0.98 Mn 0.02 )O 3 ; x =0.05–0.25 using conventional mixed-oxide method. Dielectric and piezoelectric properties of these doped ceramics were measured at room temperature. Microstructural and compositional analyses have been carried out using scanning electron microscope (SEM) and X-ray diffraction (XRD). The Curie point versus the amount of Sr composition was also investigated. Surface acoustic wave (SAW) properties, including phase velocity and electromechanical coupling coefficient, were measured. The experiments successfully showed that Sr additive is helpful to obtain higher phase velocity and high electromechanical coupling coefficient. The SAW properties of our samples ( V p , k 2 ) are better than the commercially-made PZT and PT samples.

Effects of strontium on the surface acoustic wave properties of Sm-modified PbTiO3 ceramics.

The Sm-modified lead titanate ceramics with a composition of (Pb(0.88-x)Sr(x)Sm(0.08))(Ti(0.98)Mn(0.02))O(3); x = 0.05-0.25 were prepared by conventional mixed-oxide method. Surface acoustic wave (SAW) properties, including phase velocity, electromechanical coupling coefficient and temperature coefficient of frequency, were measured. The experiments successfully showed that Sr additive is helpful to obtain higher phase velocity and high electromechanical coupling coefficient. The SAW properties of our samples (V(p),k(2)) are better than some commercially-made PZT and PT samples.

The effects of ZnO films on surface acoustic wave properties of modified lead titanate ceramic substrates

Poly-crystal zinc oxide (ZnO) films with c-axis [002] orientation have been successfully grown on the strontium (Sr) modified lead titanate ceramic substrates with different Sr dopants by r.f. magnetron sputtering technique. Highly oriented ZnO films with c-axis normal to the substrates can be obtained under a total pressure of 10 mTorr containing 50% argon and 50% oxygen and r.f. power of 70 W for 3 hours. Crystalline structures of the films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The phase velocity, electromechanical coupling coefficient arid temperature coefficient of frequency of surface acoustic wave (SAW) devices with ZnO/IDT/PT (IDT, inter-digital transducer; PT, PbTiO/sub 3/ ceramics) structure were investigated. The devices with ZnO/IDT/PT structure shows that the ZnO film effectively raise the electromechanical coupling coefficient (k/sup 2/) from 3.8% to 9.9% of the device with the concentrations of Sr dopants of 0.15. It also improves the temperature coefficient of frequency of SAW devices.

Doping Effects on the Piezoelectric Properties of Low-Temperature Sintered PbTiO3-Based Ceramics for SAW Applications

The Sm-modified lead titanate ceramics with a composition of (Pb0.85Sm0.1) (Ti0.98Mn0.02)O3 piezoceramics, doped and undoped with BiFeO3 (BF) and Ba(Cu0.5W0.5)O3 (BCW) oxides, were prepared by conventional mixed-oxide method, using sintering temperature at 1075°C and 1100°C. Microstructural and compositional analyses of the PbTiO3-based ceramics have been carried out using XRD and SEM. The effects of dopants on the sintering temperature and piezoelectric properties of the ceramics have been investigated. We successfully showed that these additives were helpful in lowering of the sintering temperature and still keep high thickness electromechanical coupling coefficient, kt, and small planar electromechanical coupling coefficient, kp. Surface acoustic wave (SAW) filters were fabricated and the phase velocities were measured.

Effects of poling field on the dielectric and piezoelectric properties of Cd additive Sm-modified PbTiO3 ceramics

Abstract (Pb 0.85− x Cd x Sm 0.1 )(Ti 0.98 Mn 0.02 )O 3 ; x =0.01–0.08 ceramics were prepared by conventional mixed-oxide technique using sintering temperature at 1150 °C and poling field at 0–70 kV/cm. Microstructural and compositional analyses of these doped ceramics have been carried out using X-ray diffractometer (XRD) and scanning electron microscope (SEM). The effects of the poling field on the dielectric and piezoelectric properties of Cd additive Sm-modified PbTiO 3 ceramics have been investigated. We successfully showed that the thickness electromechanical coupling coefficient, k t , of the Cd additive samples is larger than 0.54 as poling field higher than 40 kV/cm, and still keep small planar electromechanical coupling coefficient, k p .

Effects of sintering temperature on the piezoelectric and dielectric properties of Cd additive Sm-modified PbTiO3 ceramics

Abstract (Pb 0.85− x Cd x Sm 0.1 )(Ti 0.98 Mn 0.02 )O 3 , x =0.01∼0.08, were prepared by conventional mixed-oxide techniques, using sintering temperatures of 1075–1175 °C for 2 h. Microstructural and compositional analyses of these doped ceramics have been performed using XRD and SEM. The effects of sintering temperature on the piezoelectric and dielectric properties of Cd additive Sm-modified PbTiO 3 ceramics have been investigated. We successfully show that the Cd additive samples have maximum thickness electromechanical coupling coefficient, k t (>0.56), at Cd=2 mol% for a sintering temperature of 1150 °C, and still keep small planar electromechanical coupling coefficient, k p . In other words, the preferred sintering condition was found.