| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2001: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1999: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
The following results were obtained in this research :
(1) The compounds of Ba_3Ga_2Ge_<4-x>Si_xO_14, Ba_3Ga_2Si_<4-x>Sn_xO_14, Ba_3Nb_xGa_<x+2>Si_<4-2x>O_14, Ba_3Ga_2Ge_<4-x>Sn_xO_14 (x > 0.5), Ba_<3-x>Ca_xNbGa_3Si_2O_14 (0 < x < 3) have been regretfully not langasite structures.
(2) After permuting the A site by Ba, Ba_3Ga_2Ge_4O_14 (BGG) has the langasaite structure and has large lattice constants. Crystal growth of BGG has been tried, but quality crystal was not achieved. The Bridgman technique might be effective for this material.
(3) Single crystal of Ca_3NbGa_3SiO_14 (CNGS), which has the langasite structure, has been successfully grown. But its piezoelectric constant |d11| was about 4x10^<-12> C/N, that smaller than expected by a/c ratio.
(4) According to the result of CNGS crystal, the piezoelectric constant d may be proportional to lattice constant a, not be proportional to a/c ratio. The crystal growth method for large lattice materials has to be modified. The Bridgman technique may be effective.
(5) All elastic, piezoelectric and dielectric constants, and their first and secondary temperature coefficients of La_3Ga_5SiO_14 (LGS) and La_3Ta_0.5Ga_5.5O_14 (LTG) crystals have been measured.
(6) Rayleigh SAW properties of LGS crystal with propagation direction of (0°, 140°, 25°) was simulated ; velocity ν(free) = 2750 m/s, electromechanical coupling factor κ^2 = 0.36 %, temperature coefficient of delay TCD = 0, power flow angle PFA = 2°.
(7) Rayleigh SAW properties of LGS crystal with propagation direction of (15°, 151°, 40.5°) was calculated ; ν(free) = 2860 m/s, κ^2 = 0.41 %, TCD = 0, PFA = 0°.
(8) The SAW properties of LGS were measured by using SAW filters. The measured results have good agreement with the simulation results.
(9) Rayleigh SAW properties of LTG crystal with propagation direction of (13°, 150°, 36°) was simulated ; ν(free) = 2690 m/s, κ^2 = 0.5 %, TCD = 0, PFA = 0°.
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