Growth of high resistivity RbTiOPO₄ crystals

RbTiOPO₄ crystals have been grown by the top-seeded solution method from self-fluxes containing [Rb]/[P] molar ratios as high as 2.3 and initial solute concentrations of 1.2 g-RTP/g-flux, corresponding to the previously unexplored part of the RTP crystallization field in the Rb₂O-P₂O₅-TiO₂ ternary system. The Curie temperatures of as-grown crystals corresponding to the high-temperature ferroelectric phase transitions have been determined using the standard dielectric (capacitance) technique and found to exceed 790 °C. The results indicate that the Curie points shift to higher values as compared with crystals grown from fluxes with lower [Rb]/[P] molar ratios, as expected, still maintaining the usual linear dependence between the Curie point magnitude and flux chemical composition. However, the room temperature dc resistivity is distributed uniformly within a large single crystal, both radially and axially, reaching high values between 10¹¹ and 10¹² Ω cm. The temperature dependence of the ac conductivity has been studied as well and discussed in terms of the site-occupancy of Rb⁺-ions and ionic migration paths in nearly stoichiometric RTP crystals.