US 12,439,824 B2
Diffusion bonding of piezoelectric crystal to metal wear plate
Gnanasekaran Thiagarajan, Kalpakkam (IN); Lakshmi Gandhan I.Ilango, Kalpakkam (IN); Asokane Cannessane, Kalpakkam (IN); Jeyan Ramamurthy Mattamanna, Kalpakkam (IN); and Saju Thomas Abraham, Kalpakkam (IN)
Assigned to Secretary, Department of Atomic Energy, Mumbai (IN)
Appl. No. 17/436,963
Filed by SECRETARY, DEPARTMENT OF ATOMIC ENERGY, Mumbai (IN)
PCT Filed Mar. 23, 2019, PCT No. PCT/IB2019/052373
§ 371(c)(1), (2) Date Sep. 7, 2021,
PCT Pub. No. WO2020/194026, PCT Pub. Date Oct. 1, 2020.
Prior Publication US 2022/0173305 A1, Jun. 2, 2022
Int. Cl. H10N 30/073 (2023.01); H10N 30/06 (2023.01); H10N 30/87 (2023.01); H10N 30/88 (2023.01)
CPC H10N 30/073 (2023.02) [H10N 30/06 (2023.02); H10N 30/877 (2023.02); H10N 30/88 (2023.02)] 8 Claims
OG exemplary drawing
 
1. A method of diffusion bonding of a lead zirconate-titanate (PZT) piezoelectric crystal to a metal wear plate for fabrication of a high temperature ultrasonic transducer comprising the steps of:
i. depositing a first coating of a noble metal on a bonding surface of the PZT crystal;
ii. depositing a second coating of the noble metal on a bonding surface of the metal wear plate;
iii. bringing the bonding surfaces of the noble metal coated PZT crystal of step (i) and the bonding surface of the noble metal coated metal wear plate of step (ii) into contact with each other and heating under pressure ranging from 175 to 225 bar and at a temperature ranging from 270 to 400° C. to form a metallic bond to obtain a lead zirconate-titanate (PZT) piezoelectric crystal diffusion-bonded to the metal wear plate by a noble metal interlayer under vacuum;
wherein, the metal wear plate is selected from nickel and nickel alloys; and
wherein the metal interlayer is able to withstand a prolonged exposure to high temperature up to 250° C. and repeated thermal cycling.