Sakichi Ashida

Temperature‐compensated PbTiO3 ceramics for surface acoustic wave applications

Lead titanate PbTiO3 ceramics with a zero temperature coefficient of surface wave delay time are developed by addition of Nd2O3, In2O3, and MnO2. These ceramics have very small temperature coefficients of less than 1 ppm/ °C over a wide temperature range (−10–+60 °C). They have a large electromechanical coupling factor and low dielectric constant. The propagation loss is 4 dB/cm at 57 MHz. These modified PbTiO3 ceramics have high potential for use in surface wave applications, e.g., filters.

Surface acoustic wave properties of (Pb,Ln)(Ti, Mn, In)O3 ceramics (Ln = La and Nd)

The surface acoustic wave properties of PbTiO3 ceramics are improved. The ceramic systems investigated are (Pb,Ln)(Ti,Mn,In)O3(Ln = La,Nd). The temperature coefficients of delay time are lowered to 46×10−6/ °C, when Ln is La. A zero temperature coefficient of delay can be achieved when Ln is Nd. The Nd and In substitution also cause the electromechanical coupling factor to increase and the dielectric constant to decrease.

Surface acoustic wave characteristics of (Ba2−xSrx)TiSi2O8 crystals

The surface acoustic wave characteristics of fresnoite (Ba2TiSi2O8) crystals are improved. The temperature coefficients of delay time are greatly lowered, with almost no change in the electromechanical coupling factor, as the result of partial substitution of Sr for Ba, particularly in (Ba2−xSrx)TiSi2O8 crystals. These crystals have temperature coefficients of delay comparable to LiTaO3, while their electromechanical coupling factors are twice as large.

Piezoelectric Ceramics with Zero Temperature Coefficients of Radial Mode Resonance Frequencies

Piezoelectric ceramics with zero temperature coefficients of radial mode resonance frequencies were developed. The chemical formula of these ceramics is (Pb0.91(La1-αNdα)0.08)(Ti0.92Mn0.02In0.06)O3. In the ceramic system, the temperature coefficient varies from -25×10-6/°C to +40×10-6/°C as the molar ratio of Nd changes from 0 to 1. When α=0.5, the temperature coefficient is less than 1×10-6/°C over the temperature range -10 to +50°C. The electromechanical coupling factor of radial mode is 0.1; mechanical quality factor is 1400; and dielectric constant e33T is 225.

New Piezoelectric Ceramics with Zero Temperature Coefficients for Acoustic Wait Applications

Lead titanate (PbTi03) ceramics having zero temperature coefficients in various acoustic wave modes are developed by addition of Nd2O3, and Mn02. The chemical formulae of these ceramics are generally expressed by (Pbl 3,+lZNd,) (Til-y-zM”yInz)03. These ceramics have very small surface wave delay time temperature coefficients (less than 1 x 10-6/OC) over a wide temperature range (-loo to +6OoC) with appropriate compositions. Furthermore, it is possible to reduce the resonance frequency temperature coefficients in bulk wave modes (radial mode, thickness mode, flexure mode) to the same order as for surface waves by appropriately changing the combination of Nd, Mn, In concentrations. These modified PbTi03 ceramics are thus potential materials for acoustic wave applications. As application examples, SAW filters (60, ~OOMHZ), tuning fork resonators (3OkHz), and thickness mode resonators (4wz) are fabricated using these ceramics. In203

Growth and SAW Properties of (Ba2-xSrx)TiSi2O8 Crystals

Part of the phase diagram of a (Ba2-xSrx)TiSi2O8 system is demonstrated and then (Ba2-xSrx)TiSi2O8 (x≤1.0) single crystals are grown by the Czochralski (CZ) technique and the edge-defined film-fed growth (EFG) technique. The crystal composition, particularly the Sr concentration, of a CZ grown crystal varies according to the normal freezing distribution. The Sr concentration of an EFG grown crystal is almost constant. The excellent SAW properties; low temperature coefficients of delay and high electromechanical coupling factors of the grown crystals are also described.

Elastic properties of modified pbtio3 ceramics with zero temperature coefficients

Abstract Lead titanate PbTiO3 ceramics, with a zero temperature coefficient of surface acoustic wave delay time (TCD), have been developed by substituting appropriate amounts of Nd, Mn and In. The elastic, piezoelectric and dielectric constants, and their temperature coefficients, are measured for these ceramics using resonance methods. The TCD is numerically analyzed using the measured data. It is found that their temperature coefficients of elastic stiffness constants, C E 11 C E 12, C E 13, and C E 33 are all positive, though that of C E 44 is a small negative value. It is also found that these unusual temperature characteristics cause the TCD to reduce to zero.

Dislocation etch tunnels in NdxY1-xP5O14 crystals

Abstract Defects in single N x Y 1− x P 5 O 14 and NdP 5 O 14 crystals grown by a flux evaporation method using phosphoric acid are studied by etching. An interesting etching characteristic observed is the formation of etch tunnels which propagate into the crystal from etch pit apices on the as-grown crystal faces. The etch tunnel distribution indicates that the dislocations appearing in the form of these tunnels extend from the nucleation site of the crystal to the outcrops on the crystal faces. These are grown-in dislocations. Etch tunnels connected to growth hillocks on the crystal faces are found to be probably due to dislocations having a screw component.