G.M. Loiacono

Growth of large single crystals of KTiOPO4 (KTP) from high-temperature solution using heat pipe based furnace system

Abstract A process is reported for crystal growth of KTiOPO4 from its solution in K6P4O13 using a seeded, slow cooling technique. A new furnace system is reported for use in the process, its key feature being a heat pipe providing for a high degree of spatial temperature uniformity throughout the growth solution. Initial surface dissolution appears necessary to achieve flaw-free growth immediately off a seed. Avoidance of solution inclusion flawing in advanced stages of growth requires a crystal orientation configuration and rotation pattern that does not give rise to stable regions of uncirculating growth solution. Through the process, 10-day growth runs routinely produce flaw-free crystals large enough to yield plates 10 × 10 × 7 mm3 oriented in the optimal direction for second harmonic generation having properties measured to be at least as good as KTiOPO4 grown by other methods.

Flux growth and properties of KTiOPO4

Single crystals of KTiOPO4 (KTP) have been grown from flux compositions situated within the KPO3-K4P2O7 binary system. Crystals up to 15 × 15 × 5 mm in size were obtained from pure and modified fluxes. The solubility of KTP in the flux composition K6P4O13 has been determined between 1050°C and 580°C. Growth of KTP has been performed using the following techniques: spontaneous nucleation; slow cooling in a furnace equipped with accelerated crucible rotation (ACR) and cooling finger; gradient transport at constant ΔT; and top-seeded solution growth. A mechanism for the molecular formation of KTP is postulated. Thermal analysis of crystalline KTP using DTA has been performed in air and argon atmospheres; the results indicate that the compound melts with decomposition at 1172 and 1158°C, respectively. The transmission properties of KTP have been measured between 5000 and 200 nm. X-ray powder diffraction data for KTP have been refined.

Optical properties and ionic conductivity of KTiOAsO4 crystals

Crystals of KTiOAsO4 were grown by the high temperature solution method and their optical and ionic conductivity properties evaluated. The band edge and IR cutoff were 370 and 4850 nm, respectively. A domain structure prevented efficient frequency conversion in as‐grown crystals. The ionic conductivity at 22 °C and 120 kHz was 1.5×10−8, 7.3×10−9, and 1.7×10−6 S/cm for the [100], [010], and [001], respectively. The alleged ferroelectric Curie temperature was 852 ±2 °C.

Crystal growth and characterization of ferroelectric CsTiOAsO4

Abstract The synthesis and crystal growth conditions for orthorhombic CsTiOAsO 4 have been established. Crystals measuring up to 15×22×32 mm were grown at temperature lowering rates of 1 to 5°C/day. The ferroelectric nature of the phase transition at 671°C was proven by hysteresis loop measurements. The conductivity and dielectric properties are significantly different from both KTiOAsO 4 and KTiOPO 4 .

Growth of KH2PO4 crystals at constant temperature and supersaturation

Abstract A large (144 liter) three-zone crystallizer system was constructed for growing KH 2 PO 4 crystals under conditions of constant temperature and supersaturation. Crystal growth rates exceeding 5 mm day -1 were demonstrated for KH 2 PO 4 using seeds measuring 5 × 5 cm in cross section.

Dielectric, pyroelectric, and thermal properties of LiNH4SO4 and LiND4SO4

Measurements of optical second harmonic generation, specific heat, dielectric constant, and pyroelectric coefficient of LiNH4SO4 and its deuterated analog are reported over a temperature range which includes the two phase transitions near 283 K and 459 K. The results indicate that these materials are potentially useful as pyroelectric detectors. Pyroelectric and second harmonic generation data show that the phase below ∼ 283 K is polar.

The taper effect in KH2PO4 type crystals

The phenomenon of tapering in KH2PO4 type crystals is shown to be directly related to the bulk supersaturation of the growth solution. Impurity effects are found to be insignificant.

Observation of complex domain walls in KTiOPO4

Optical nonuniformities observed in second‐harmonic generation experiments on large KTiOPO4 crystals (dark line defects) are shown to be directly related to the presence of complex domain walls. It is unlikely that these domains are ferroelectric; however, their polar nature suggests they may be similar to the Dauphine twins observed in quartz.

Solubility and crystal growth of KTiOPO4 in polyphosphate solvents

Abstract The solubility of KTiOPO4 in K4P2O7, K8P6O19 and K15P13O40 solvents was determined over the temperature range 900 to 980°C. The slope of the solubility curves were dS/dT−3.4x10-3, 2.3x10-3 and 2.1x10-3 g (KTP)/g(flux)·°C, respectively Significant habit modification is observed for crystals grown from K4P2O7.

Solution growth of L(+) hydrazonium tartrate☆

Abstract Optically clear single crystals of L(+) hydrazonium tartrate, N2H4 · C4H6O6, 2 cm on an edge were grown with difficulty from aqueous solution. Crystal growth is accomplished under an argon atmosphere using the temperature lowering method over the range 45 to 30°C. The argon inhibits the formation of oxidation decomposition products for up to 8 weeks at 40°C. The crystal morphology, relative growth velocities, relative supersaturation, and the effect of deuterium on the solubility are discussed.