2016, Vol.26, No.4

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

The conditions for chemical polishing and etching technique were investigated to reveal surface defects in RE : YAG (RE = Nd3+, Er3+, Yb3+) single crystals grown by Czochralski method. The optimal condition for chemical polishing was in 85 % H3PO4 solution at 330oC for 30 minutes with a specimen fixed in the vertical direction. In addition, the optimal condition for chemical etching was in 85 % H3PO4 solution at 260oC for 1 hour, and 70~80 μm sized triangular etch pits were observed on (111) face. As a result of defect density analysis, 1.9 × 103/cm2 for Nd(1 %) : YAG, 4.3 × 102/cm2 for Er(7.3 %) : YAG, and 5.1 × 102/cm2 for Yb(15 %) : YAG were measured.

It was observed that the single grain of crystallite growth behavior in AlN (Aluminum Nitride) single crystal growth by PVT (Physical Vapor Transport) method. The single grain of AlN was grown in sequent experiments and adjacent crystallites were joined together after small grain was grown. The sequential results of those grains observed by stereoscopic microscope were reported.

Effects of the shape and size of the piezoelectric materials on the performance of tonpilz transducers were studied with a computer simulation using a finite element method (FEM). The diameter and height of the donut-shaped piezoelectric ceramics head mass were changed as variables. And the effect of the stack number was also investigated. Finally, if the piezoelectric ceramics were changed to a piezoelectric single crystal having high piezoelectric constants, how the performances especially, the output power and the TVR transmittance were affected was simulated by FEM. As a result, the output of transducer could be increased to 10 times of PZT-4 with replacement of relaxor single crystal of the same size.