Ferroelectric lithium niobate (LiNbO3) is widely used in integrated and guided-wave optics because of its favorable optical, piezoelectric, electro-optic, elastic, photoelastic, and photorefractive properties. However, detailed summaries of its pertinent physical properties and crystal structure are not readily available. In this tutorial paper, the important tensor physical properties and their mathematical descriptions are compiled and presented. The essential features of the structure of lithium niobate, including its hexagonal and rhombohedral unit cells, are illustrated and the principal (Cartesian) axes used in the description of the anisotropic properties are specified relative to the crystal structure. Errors in property coefficient values and structure information that have been propagated in the literature are corrected.

Lithium niobate: Summary of physical properties and crystal structure

The elastic, piezoelectric, and dielectric constants, and their temperature dependence within the range 0°–110°C, have been determined for single crystals of lithium tantalate and lithium niobate. For each material, the constants were extracted from a combination of many ultrasonic phase‐velocity measurements, the measured resonant and antiresonant frequencies of a single length‐extensional bar resonator, and the measured low‐frequency capacitances of two thin flat‐plate specimens. For lithium tantalate, the normalized first temperature derivatives of the elastic constants range from −0.4 to −6.7×10−4/°C, while the derivatives for the piezoelectric stress constants range from −1.3 to +1.5×10−4/°C. In the case of lithium niobate, the elastic constant temperature derivatives are all on the order of −2×10−4/°C, while the piezoelectric temperature derivatives are all positive in the range 0.8–8.9×10−4/°C. The dielectric or permittivity temperature derivatives are positive for both materials.

Temperature Dependence of the Elastic, Piezoelectric, and Dielectric Constants of Lithium Tantalate and Lithium Niobate

Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review.

The interaction of Ti${\mathrm{O}}_{2}$(110) with ${\mathrm{O}}_{2}$, ${\mathrm{H}}_{2}$, CO, and C${\mathrm{O}}_{2}$ was studied by means of low-energy electron diffraction, x-ray photoelectron spectroscopy, electron energy-loss spectroscopy, thermal desorption, electron paramagnetic resonance, and measurements of changes in surface conductivities, $\ensuremath{\Delta}\ensuremath{\sigma}$, and work functions, $\ensuremath{\Delta}\ensuremath{\phi}$, for $300\ensuremath{\le}T\ensuremath{\le}1000$ K with particular emphasis on surface reactions involving intrinsic surface defects $2{\mathrm{Ti}}^{3+}\ifmmode\cdot\else\textperiodcentered\fi{}V_{O}^{}{}_{}{}^{(+)}$. The defects are thermodynamically stable at high temperatures and act as donors and specific adsorption sites for ${\mathrm{H}}_{2}$ and CO. Surface and subsurface reactions involving ${\mathrm{O}}_{2}$, ${\mathrm{H}}_{2}$, CO, and C${\mathrm{O}}_{2}$ can be separated from each other by analyzing the $\ensuremath{\Delta}\ensuremath{\sigma}$ and $\ensuremath{\Delta}\ensuremath{\phi}$ effects in a charge-transfer model, which takes into account surface and bulk electronic states in the band gap attributed to the different defects formed during the interaction.

Intrinsic defects of Ti O 2 (110): Interaction with chemisorbed O 2 , H 2 , CO, and C O 2

Relaxor-based ferroelectric single crystals: growth, domain engineering, characterization and applications.

The temperature characteristics of dielectric constants, spontaneous polarization, thermal‐expansion coefficients, indices of refraction, and optical rotatory power of Pb5Ge3O11 single crystals have been investigated in detail from room temperature up to above the Curie temperature, 177°C. From the results of these measurements, the following constants were obtained: linear thermal‐expansion coefficients (αa)F=7.75×10−6/deg°C and (αc)F=7.79×10−6/deg°C (ferroelectric phase), (αa)P=13.8×10−6/deg°C and (αc)P=13.4×10−6/deg°C (paraelectric phase); quadratic electro‐optic constants g33T=0.47×108 cm4 /C2, g13T=0.37×108 cm4 /C2; and electrogyration coefficient γ33 =8.7 cm2/C. An isomorphous compound Pb5(Ge2O7)(SiO4) was synthesized and was found to be ferroelectric with T c=60°C and Ps=1.7 μC/cm2 at room temperature. Ferroelectric properties and electrogyration coefficient were studied in the solid‐solution system Pb5(Ge2O7)(GeO4)1−x (SiO4)x.

Ferroelectric and optical properties of Pb5Ge3O11 and its isomorphous compound Pb5Ge2SiO11

Dielectric constants and refractive indices of a 5PbO · 3GeO2 crystal, which was grown from the melt by by the Czochralski method, were measured as a function of temperature. The crystal was identified as a new type of ferroelectric with spontaneous polarization Ps = 0.046 C/m2, coercive field Ec ∼ 2.3 × 106 V/m at room temperature, and Tc = 177°C.

5PbO·3GeO2 CRYSTAL; A NEW FERROELECTRIC

Piezoelectric and elastic constants of lithium niobate single crystal were measured in the temperature range between 20°C and 200°C. These constants were obtained by measuring the resonant and antiresonant frequencies of the length-extensional mode of bars with various orientations. The measured constants are all of the piezoelectric strain constants and the dielectric constants and a part of the elastic compliances, namely, sE11, 2sE13+sE44, sE14 and sE33. Values at 20°C and their temperature dependence are as follows. The constants d and s are expressed in units of 10-8 statcoulomb/dyn and 10-12 cm2/dyn, respectively: d15=222[1+(T(^°C)-20)2.8×10-4]; d22=62.3[1+(T-20)×2.4×10-4]; d31=-2.59[1+(T-20)11×10-4]; d33=48.7[1+(T-20)2.9×10-4]; s11E=0.564×[1+(T-20)1.5×10-4]; 2s13E+s44E=1.39[1+(T-20)2.0×10-4]; s14E= -0.084; s33E=0.494[1+(T-20)1.5×10-4]; e11T=84.6; e33T=28.6; k31=0.02; k22=0.32; k33=0.47. The electromechanical coupling factor k'31 of zyw-45°-cut bar amounts to 0.50.

https://iopscience.iop.org/article/10.1143/JJAP.6.151/pdf

Piezoelectric and Elastic Properties of Lithium Niobate Single Crystals

https://iopscience.iop.org/article/10.1143/JJAP.3.495/pdf

An X-Ray Study on Bi 2 O 3 -Fe 2 O 3 System

Growth feature of a LiNbO3 crystal obtained by the pulling method has been studied. The formation of growth ridges was interpreted as the intermittent growth of the form {10}, which was the most readily grown form from the melt. The point group of the high temperature, paraelectric phase was uniquely determined as 2/m from the symmetry elements of the configuration of ridges. On (00) planes, the triangular etched hillocks were observed. Orientations of the hillocks on the antiparallel domains were related by 2-fold rotation axis parallel to [100] consistent with the phase transition of the type 2/m→3m. The atomic arrangement in the form {10} was examined, and a three-dimensional framework of the corner-shared Nb-O octahedra, similar to the one in perovskite, was found.

https://iopscience.iop.org/article/10.1143/JJAP.6.318/pdf

Nobukazu Niizeki

Papers

Ferroelectric and optical properties of Pb5Ge3O11 and its isomorphous compound Pb5Ge2SiO11

5PbO·3GeO2 CRYSTAL; A NEW FERROELECTRIC

Piezoelectric and Elastic Properties of Lithium Niobate Single Crystals

An X-Ray Study on Bi 2 O 3 -Fe 2 O 3 System

Growth Ridges, Etched Hillocks, and Crystal Structure of Lithium Niobate