Process for producing a single crystal of KTiOPO4 or its analogues

Claim 1

A process for producing a single crystal of MTiOXO 4 by heating starting materials comprising MTiO 2 XO 4 with a flux M/X/O, or their precursors, where M is at least one of K, Rb or T1 and X is at least one of P or As wherein the ratio of the starting materials lies within the region of the ternary phase diagram M 2 O/X 2 O 5 /(TiO 2 ) 2 where the product MTi O XO 4 is the only stable solid phase in equilibrium with the flux when molten, which comprises a process selected from the group consisting of A(1) heating the starting materials, in which the ratio of the starting materials is also such that the ratio of MTiOXO 4 to flux at the highest temperature reached is greater than the saturation value, in a temperature gradient where the hot zone is in the range of about 800°C to about 1000°C and the cold zone is in a range about 10°C to about 135°C cooler, to produce a melt, (2) maintaining the temperature gradient for about 3 days to about 3 weeks to allow crystal growth, and (3) cooling and recovering crystalline MTiOX0 4 , and B(l) uniformly heating the starting materials, in which the ratio of the starting materials is also such that the ratio of MTiOXO 4 to flux at the highest temperature reached is less than the saturation value, to a temperature range of about 700°C to about 1100°C until a clear solution is obtained, (2) slowly cooling the solution at a rate no greater than 5°C per hour to cause crystallization of MTiOX0 4 and recovering same.