Patent ID: 7211234

Claim:
A method for making tetragonal lanthanide vanadate crystals having the formula LnVO 4 wherein Ln is selected from the group consisting of La, Nd, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y and combinations of at least two thereof, comprising the steps of: reacting a source of Ln 3+ ions and a source of VO 4 3− ions, wherein Ln is selected from the group consisting of La, Nd, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y and combinations of at least two thereof, in an aqueous solution at a temperature of from about 350° C. to about 600° C. and at a pressure of from about 8 kpsi to about 40 kpsi, the aqueous solution comprising hydroxide ions at a concentration of from about 0.01 to about 5 molarity.