Ferroelectric phase transition temperatures of KTiOPO4 crystals grown from self-fluxes

Abstract

The origin of diversity in the reported ferroelectric phase transition (Curie) temperatures Tc, of KTiOPO4 (KTP) crystals grown from self-fluxes has been studied. A series of crystals has been grown by the top-seeded solution method from fluxes of different K/P molar ratios and solute concentrations, covering most of the KTP crystallization field in the K2O–P2O5–TiO2 ternary system. Curie temperatures of as-grown and high-temperature annealed crystals have been measured using the standard dielectric technique and found to spread from 883 to 960 °C. We show that the actual Tc values depend on the solution chemical composition, and a functional representation of this dependence is given. Inherent gradients of the Tc in as-grown KTP crystals are discussed in terms of the nonuniformity of their physical properties.

Growth of high resistivity RbTiOPO4 crystals

“…Clearly, the trendline of R ¼ 2.3 is located above the trendlines corresponding to solvents with lower R-values, and the Curie temperature for this solvent rises nearly linearly with the decrease of the RTP concentration as well. This is accord with the case of KTP [8], and we can state the following: (a) the lower is the RTP concentration, in any self-flux, the higher is the Curie temperature of the crystal and (b) for any given RTP concentration in the flux, the Curie temperature is higher for self-fluxes with higher values of R.…”

“…In similarity with KTP [8], the specific value of the ferroelectric transition (Curie) temperature can be a good measure of the degree of rubidium stoichiometry in RTP crystals grown from self-fluxes, namely rubidium phosphates with differing [Rb]/[P] molar ratios. The larger is this ratio, or the richer (in rubidium) is the flux, the higher is the rubidium content in the crystal, which is manifested in its higher Curie temperature.…”

Structural Reasons for the Nonlinear Optical Properties of KTP Family Single Crystals

“…Physical properties of single crystals grown by top-seeded solution method were studied at the Ariel University Center of Samaria using the technique in [41][42][43]. Physical properties of single crystals grown by spontaneous flux crystallization were studied at the Faculty of Physics of the Moscow State University jointly with the Karpov Institute of Physical Chemistry [33].…”

Growth of KTP crystals with large {001} facets

“…T c E959 1C in hydrothermal crystals [14]. Here again, the higher is the Curie temperature, the better is the stoichiometry [5]. Figure 4 shows the Curie temperatures measured using samples cut from the top and bottom parts of the (0 0 1) growth sector column.…”

“…Due to the relatively fast growth in the Z-direction, the crystal-melt interface is typically a pyramid or trapezoidal prism [4] engulfed in two pairs of (0 1 1)-and (2 0 1)-type facets, while only a very narrow or none (0 0 1)-type facet is formed. Since KTP growth from pure self-fluxes yields crystals with gradually varying K-content [5], the K-stoichiometry is definitely expected to vary across any Z-cut plate. A possible solution to this problem, namely finding a way of growing KTP crystals with welldeveloped {0 0 1} facets, is modifying the flux chemical composition.…”