If you suspect the texture effect, try other (several) orientations of the sample. 

However, your question evokes a general question to existing XRD approaches to determination of phases, particularly with small fractions as retained austenite in steel. Namely, we derive the fraction in terms of this phase-to-matrix peak intensity ratio FROM FIRST PRINCIPLES.  In other words, no DIRECT verification of the method is used.

It is a more principal drawback that wants to be somehow eliminated with appropriate reference (etalon) specimens of certain phase composition. Hopefully, much more intense neutron diffraction will enable fabricating such specimens.

Since rutile is tetragonal you can use March-Dollase approach. Old but for axial systems like tetragonal, hexagonal, rhombohedral/trigonal and perhaps monoclinic acceptable. Newer texture models also work as long as the integral over all reflection multiplicities is constant. Is there absolutely no intensity? Could you post the data?

For not that extremely textured material the phase composition keeps surprisingly stable. Not totally, but if you switch between texture and no texture the variation is somehow balanced. Some peak have more other less intensity. However, the more reflections you have the better the balance.

Is it possible to mill your sample in order to get a powder like one having less texture? So you will have access to all peaks. 

My TiO2 samples are in powder form with nanotubular structures as shown in the attached figure. The XRD pattern of my sample obtained from Bragg Brentano XRD is attached here. I noticed major rutile peak along with other peaks when i took parrallel geometry XRD for my sample. But my question is if there exists a way to find the phase contents if the major peak is absent in the XRD pattern.

Thank you all for your valuable replys.

I simulated the two extereme possibility with preferred orientation along 001 with march dolase 0.5 and 1.5.  If u scan ur sample with the condition as on ur SEM image than the c-axis was perpindicular with the diffraction vector, so the main peak (110) is less preferred. U need o look for 011 (~36 2theta).

To get the good result u need to grind ur sample, backload preparation (or use spinner) and re-take the data with longger scan time and small step scan.

Hi Dr.Maykel Manawan,

I didnt get the 50% rutile peak (101) at around 36 2theta. May i know which software you used to simulate the patterns for specified orientations? If its possible for you to send me the .cel file? 

The thing is that you either should use some assumptions about orientation distributions (which may be correct, or erroneous if you are particularly unlucky and your material is more complex than you believe)... Or you can try and measure sample in different orientations and get both composition and preferred orientations of phases. You may try using MAUD to model diffraction pattern with preferred orientations, in particular the Standard Functions ODF functionality there would be very useful. 

Dear Dr. Preethi Kuppusamy

What I did just a simple simulation doesn't mean to validate the quantity of the phases. U need to do Rietveld refinement. MAUD is one of dedicated software to handle such preferred orientation as Dr Roman suggested.

Ur sample also containing anisotropy shape broadening and size broadening.

If u dont mind u cud post one of ur raw data.

I used HS+ and the quantity was purposely set. Gemme sometimes about the CIF file

Thank you Dr. Roman and Dr. Maykel for your valuable suggestions. Herewith attached the raw data of the XRD pattern i have shown previously in this discussion.  

If you have nano-tubes I would expect a strong texture or preferred orientation. The very strong discrepancy in thinckness also indicate the anisotropic peak broadening. Surprizing to me is peak asymmetry also at higher angles. In fact, you sample describes a case where practically everything is breaking the rules for a proper XRD experiment and also simulation. I hardly doubt that you can meaningful simulate this.

As long as you do not have any ideas from where these tails to higher Bragg angles come I would not bet a wager about the quantitative results. Quantitative XRD is only accurate if you fullfill the requirements to your sample: homogeneus sample (chemistry, grain dimension), grain size (not particle size) in the scale of 0.5µm, careful sample preparation. 

Dear Dr. Preethi Kuppusamy

Seems like u normalized the intensity, so i get less tha n 100 cts. Anyway, here is the result from Maud also the .CIF file for those 3 TiO2 polymorph.