Prof. Paul Gillis of the Univ. of Kansas (USA) around 1966 published a complete phase diagram of the system titanium and oxygen (and others including Vanadiam and tungsten).  The work was funded by our Atomic Energy Commission at the time, and the end use was in nuclear reactors, so the temperature ranges were quite large. The AEC was subsequently morphed into the current Nuclear Regulatory Agency.   I suggest you seek his publications for guidance on the conditions leading to anatase, rutile, or brookite forms of titanium dioxides. 

Unfortunately, I do not have his publications to offer.  I only know of his work because I worked as an undergraduate technician in his research group at that time, and saw both the work-up and final publication of his very extensive work.

Dear Mabkhoot,

TiO2 Anatase phase begin to form at 200°C, some studies have shown that the best temperature is 400°C, above this temperature TiO2 begins to form some rutilo phase, but insignificant amount. 

Maybe you did not wait the proper time to complete the annealing. How much time did you left your sample annealing?

Best regards,