Baoliang Lu

Seeded Growth of Relaxor Ferroelectric Single Crystals Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 by the Vertical Bridgman Method

Relaxor ferroelectric single crystals Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT91/9) with a dimension of 30 mm in diameter and 25 mm in length have been grown by the modified vertical Bridgman method using PbO as the flux. Initially, seed crystals were obtained by cooling high-temperature solutions at the rate of 0.8–2°C/h. PZNT91/9 crystals were grown in a platinum crucible with a seed well of 10 mm×60 mm from different solutions. It is difficult to grow perovskite PZNT crystals from 91 mol% Pb(Zn1/3Nb2/3)O3–9 mol% PbTiO3 melts with a surplus of PbO due to the competition of the pyrochlore phase. Additionally, a Pt crucible is prone to severe erosion by PbO at high growth temperatures. The optimum flux concentrations were found to be 45–55 mol% and the growth rate was 0.3–0.6 mm/h. Twelve pieces of PZNT wafers without any PbO striation were obtained. The dielectric properties of the grown crystals were determined.

Growth and Ferroelectric Properties of PZNT Single Crystals from High Temperature Solution

The solid solution crystal Pb(Zn1/3Nb2/3)O3-PbTiO3 [PZNT] has been grown from the high temperature solution. The crystallization behavior of PZNT was investigated. The evaporation of PbO was controlled by sealing crucible and the erosion of the melt or solution on Pt crucible was discussed. By optimizing growth conditions, high quality PZNT crystal was obtained. The ferroelectric properties were measured and the results showed as–grown crystal has high performance.

Growth and Etching Studies of MgO-Doped LiNbO3 Single Crystal

LiNbO3 (Mg:LN) crystal is an important electro-optical material and MgO-doped LiNbO3 was expected to improve its optical damage resistance. In the present work, we reported the Bridgman growth of MgO-doped LiNbO3 crystal. The growth parameters were discussed and the defects were investigated by the chemical etching method. The etch hillocks and etch pits were observed on the negative Z surface while only etch pits on the positive Z surface by the optical microscope and EPMA. The etching morphology was discussed considering the domain structure.

Bridgman Growth of a Novel Piezoelectric Single-Crystal Material: Ca3NbGa3Si2O14

Langasite (La3Ga5SiO14, LGS) and its isomorphs, were regarded as potential substrate materials for surface acoustic wave (SAW) and bulk acoustic wave (BAW) applications. Among these homologous compounds, the ordered structure crystals have attracted much attention for their low Ga2O3 content, high acoustic velocity and low acoustic loss. In this work, the ordered langasite structure crystals Ca3NbGa3Si2O14 (CNGS) were grown with vertical Bridgman method for the first time. The CNGS crystals with 25mm in diameter and 40mm in length were grown successfully from its stoichiometric melt through LGS crystal of Ø10mm×40mm being chosen as seed. X-ray powder diffraction experiments showed that the CNGS single crystals had a single phase and had the same structure as the LGS crystal. The transmittance spectra with the wavelength from 200 to 800nm were recorded by means of Spectrophotometer at room temperature.

Industrial growth of lithium tetraborate (Li/sub 2/B/sub 4/O/sub 7/) piezocrystal and its SAW applications

Lithium tetraborate Li/sub 2/B/sub 4/O/sub 7/ (LBO) single crystal is a superior substrate material for surface acoustic wave and bulk acoustic wave devices due to its fairly high electromechanical coupling factor and zero temperature coefficient of frequency in [110] plane. In this paper, Bridgman growth of large size LBO crystals is presented from an industrial point of view. The improvements and advantages of the modified Bridgman method are discussed. Mass production of /spl Phi/3 4 LBO boules has been realized in our laboratory. The fabrication of SAW devices based on LBO wafers is introduced briefly.