out of different diffracted peaks, which peak we have to select for particle size calculation using Sherrer formula.
The calculation using Scherrer formula assumes a certain shape factor and generally isotropic. In real life crystals neither of those assumptions are true but far from it.
"usually an average of all peaks" will only smudge the data and give you an average "isotropic" reciprocal space parameter and hence a "smudged" interpretation. The use of "(h00), (0k0) and (00l) peaks" will give a better estimate of the an-isotropic character of the real life sample.
The broadening of X-ray diffractions reflections can be investigated using different methods: (1) the Scherrer method, (2) the Warren-Averbach approach, (3) the Langford method, (4) several whole pattern analysis approaches (Kojdecki method, Leoni method,...), (5) and others.
The parameter B ( full width at half maximum) should be converted to radians instead of degrees , so the B must be multiplied by 3.14 and divided by 180
Another point is that , cos Theta is cos ( angle /2) because the reading is 2 theta
Son Thanh Nguyen
Nagaoka University of Technology
Centre Algérien de Développement des Technologies Avancées
Swetha S M
Indian Institute Of Science Education and Research, Thiruvananthapuram
Hari Prasad Dasari
National Institute of Technology Karnataka
National Institute of Technology Rourkela
Naveen reddy Thuniki
Indian Institute of Chemical Technology
University of Queensland
Edward Andrew Payzant
Oak Ridge National Laboratory
Indian Institute of Technology Madras