• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.4 no.2
• /
• pp.134-138
• /
• 1994

$LiTaO_3 (LT)$ single crystals (Y, X-axis) were grown from the congruent composition, 48.65 mole %, $Li_2O$ for SAW (Surface Acoustic Wave) applications. Basic SAW filters were fabricated on the RIST prepared LT wafers (Y-cut) using phtolithography. SAW filter performance was evaluated. The results were compared of the SAW characteristics between RIST prepared LT wafer (Y-cut) and commercial Yamaju wafer (Y-cut). The SAW filter prepared on the RIST grown LT wafer was shown better SAW performances than that of Yamaju wafer.

• Journal of the Korean Magnetics Society
• /
• v.13 no.5
• /
• pp.204-210
• /
• 2003

Electron magnetic resonance (EMR) of paramagnetic Cr$^{3+}$, Mn$^{2+}$, and Fe$^{3+}$ impurity ions in ferroelectric LiNbO$_3$ and LiTaO$_3$ single crystals has been studied. The actual sites location of paramagnetic impurity ions in the crystals was suggested from the experimental results and zero field splitting parameters calculated by superposition model. It turns out that Cr$^{3+}$ ions in LiNbO$_3$ crystal have two resonance centers and enter both the Li$^{+}$ and Nb$^{5+}$ ions. Mn$^{2+}$ and Fe$^{3+}$ impurity ions in LiNbO$_3$ substitute for Nb$^{5+}$ ions. However, both Cr$^{3+}$ and Fe$^{3+}$ ions in LiTaO$_3$ crystal reside at Li$^{+}$ ions.$ +/ ions.+/ ions.

• Journal of the Korean Magnetics Society
• /
• v.24 no.3
• /
• pp.71-75
• /
• 2014

Ground state energy levels of the $Fe^{3+}$ paramagnetic impurity ion in stoichiometric $LiTaO_3$ and in congruent $LiTaO_3$ single crystals were calculated with electron paramagnetic resonance constants. Energy levels between six energy levels were obtained with spectroscopic splitting parameter g and zero field splitting constant D for $Fe^{3+}$ ion. The energy diagrams of $Fe^{3+}$ ion were different from different magnetic field directions ([100], [001], [111]) when magnetic field increases. The calculated ZFS energies of $Fe^{3+}$ ion in stoichiometric and congruent $LiTaO_3$ single crystals for ${\mid}{\pm}5/2$ > ${\leftrightarrow}{\mid}{\pm}3/2$ > and ${\mid}{\pm}3/2$ > ${\leftrightarrow}{\mid}{\pm}1/2$ > transitions were 12.300 GHz and 6.150 GHz, and 59.358 GHz and 29.679 GHz, respectively. It turns out that energy levels of $Fe^{3+}$ paramagnetic impurity in $LiTaO_3$ crystal are different from different crystal growing condition.

• Journal of the Korean Magnetics Society
• /
• v.15 no.3
• /
• pp.177-180
• /
• 2005

Ferroelectric $LiTaO_3$ single crystals, grown by the Czochralski method, were thermally treated at temperature $1000^{\circ}C\;and\;1100^{\circ}C$. Electron paramagnetic resonance (EPR) study of stoichiometric $LiTaO_3$ and thermally treated $LiTaO_3$ crystals has been investigated by employing an X-band spectrometer. From the $Fe^{3+}$ EPR spectra, it turned out that there is no change of site location and local site symmetry around $Fe^{3+}$ impurity ion between stoichiometric and thermally treated $LiTaO_3$ single crystals. We confirmed that the ionic state of $Fe^{3+}$ ion changed after thermal treatment. The EPR parameters of $Fe^{3+}$ ion in $LiTaO_3$ single crystals are determined with effective spin Hamiltonian.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.2
• /
• pp.193-204
• /
• 1998

The single crystal of the $LiTaO_3$has large electro-optic effects, so it is applied to optical switch, acousto-optic deflector, and optical memory device as hologram using photorefractive effect. In this study, optic-grade undoped $LiTaO_3$and Fe:LiTaO$LiTaO_3$single crystals were grown by the Czochralski method and optical transmission and absorption spectrums were measured in the wavelength of UV-VIS range. The curie temperature was determined with DSC and by measuring capacitance for the grown undoped crystal and ceramic powder samples of various Li/Ta ratio. In case of having a 48.6 mol% $Li_2O$ as a starting Li/Ta ratio, the results of concentration variations were below 0.01 mol% $Li_2O$ all over the crystal, so it was confirmed that $LiTaO_3$single crystals were grown under congruent melting composition having optical homogeneity. The curie temperature of the Fe:$LiTaO_3$crystal was increased with increased with increased doped Fe concentrations;by the ratio of $7.5^{\circ}C$ increase per Fe 0.1 wt%. Also, the optical transmittance was about 78 %, which was sufficient for optical device.

• Analytical Science and Technology
• /
• v.5 no.1
• /
• pp.115-120
• /
• 1992

The upper limit of solid solution of $Al_2O_3$ in $LiTaO_3$ was investigated using X-ray diffraction and Raman spectroscopy. By substituting cations in $LiTaO_3$ with $Al^{3+}$, the melting temperature was lowed and the ferroelectric properties can be improved. It is easier at lower temperature to fabricate the single crystal used for SAW filters and IR sensors. From the measured lattice constants and Raman band broadening, the solubility limit was X=0.25mol in $Li_{1-X}Al_{2X}Ta{1-X}O_3$, above which $Al_2O_3$ was obsered as a second phase. The Raman band of sintered $LiTaO_3$ was compared with that of the single crystal to see the effect of grain size on the band broadening.

• Journal of the Mineralogical Society of Korea
• /
• v.15 no.2
• /
• pp.140-144
• /
• 2002

The sample environment at high temperature for the four circle diffractometer at HANARO in Korea Atomic Energy Research Institute is developed. The performance test was carried out for a structurally known sample through the high temperature experiment with this equipment. In this study we found out that the developed sample environment is stable for a long time experiment at over 900 K. By the neutron diffraction from a single crystal of $LiTaO_3$(phase transition temperature about 900 K) at 298 and 913 K, the lithium atomic positions at both temperatures and disordered state of lithium atom at high temperature were confirmed. These are hardly possible to determine by the conventional X-ray diffraction method.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.7 no.4
• /
• pp.528-535
• /
• 1997

$LiTaO_3$ single crystals of congruently melting composition were grown by the halogen lamp type floating zone system. Calcination and sintering parameters for the growth were established. Optimum crystal growth conditions were investigated by a controlling of growth rates, rotation speeds and atmospheres. Based on the melting aspect and the shape of molten zone, stable conditions could not be found in air or Na atmosphere. However the growth stability in Ar atmosphere was more regular than that in air or $N_2$. The grown crystals were characterized using Laue back reflection, Curie temperature, refractive index and transmittance. Curie temperature fluctuation in the section of the grown crystal part of top, body and tail was $1^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.3 no.2
• /
• pp.99-106
• /
• 1993

A relationship $(T_c = -17.869C^2+1840.2C-46623)$ between Curie Temperature$(T_c)$ and (C), $Li_2O$ mole percent(%) was established from the measurement results of Curie temperature $(T_c)$) analysed by DTA(Differential Thermal Analysis) in the range from 48.50 to 49.00 $Li_2O$ mole %. Congruent melt composition of $LiTaO_3$ single crystal was to be 48.65 $Li_2O$ mole % and its Curie temperature was also determined to be $610{\pm}1^{\circ}C$ from the results of Curie temperature difference, ${\Delta}T (T_{c(Top)}-T{_c(Tail)})$ of Czochralski grown $LiTaO_3$ crystals and the distribution coefficient(k). The k was calculated from $LiO_2$ mole ratio of initial melt to final melt and initial crystal to final crystal in the range from 48.60 to 48.70 $Li_2O$ mole %.

• Journal of the Korean Magnetics Society
• /
• v.13 no.4
• /
• pp.171-175
• /
• 2003

Electron paramagnetic resonance (EPR) of Fe$^{3+}$ in LiTaO$_3$ single crystal, grown by Czochralski method, has been studied by employing an X-band spectrometer. Resonance spectra of Fe$^{3+}$ ion on the crystallographic principal axes were obtained with 9.447 ㎓ at room temperature. The spectroscopic splitting parameter g and zero-field splitting (ZFS) parameter D (= 3 B$_{2}$sup 0/) are calculated with effective spin Hamiltonian. Fe$^{3+}$ center in stoichometric single crystal turns out to be different with that in congruent single crystal reported previously. From the analysis of temperature dependence of resonance fields for Fe$^{3+}$ ion, there is no any phase transition at the temperature range (from -160 $^{\circ}C$ to 20 $^{\circ}C$).