LAUSR

The commented paper [1] presents the results on structural, optical and morphological studies of hexagonal zinc oxide nanorods. Unfortunately, the crystallographic part has some misleading data and statements. First of all, the formula for micro strain evaluation is wrong. The correct Wilson formula should have “cotΘ” instead “cosΘ”. Although the Wilson formula for the broadening of diffraction profile due to micro strain within the sample, is rather popular, the above error is also popular. As a result all data on the micro strain presented in the Table 1. are wrong. The correct values are of 3–5 times greater depending on the 2Θ angle. The main comment concerns the use of a texture coefficient TC in the case of powder sample containing separate grains. This coefficient can be used only for solid sample (e.g. rolled metals or thin films) where grains are closely packed and their mutual orientation is fixed. The “texture” for powder sample, if observed, can be changed from one measurement to the other. Therefore, the value of TC has no practical application and physical meaning (this is not a material property) for powder sample. And this is a case of experiment described in commented paper. Generally, the values of TC, as presented in the last column of Table 1., ranging from 4 to 10% do not indicate on the preferred orientation within the samples—they are to small. The statement that preferred grain orientation in the studied samples is along (101) direction is wrong. Firstly, due to too small values of TC and to lack of any comparison with the values in other directions. Secondly, it seems that the above statement was made on the basis of the highest X-ray diffraction peak on the diffraction pattern presented in Fig. 1. It is well known, that the texture can be seen as a highest peak with respect to that from bulk sample. This is not a case! The (101) peak in all samples has its value the same as in “standard” diffraction pattern of ZnO crystal. This is due to the crystal structure itself and not due to texture! Unfortunately, such erroneous thinking of preferred orientation along the highest peak is rather popular in other papers. Careful analysis of the diffraction patterns indicates on the errors in citing the peak position in the text. The number of positions is different the number of peaks names and some 2Θ angles are not consistent with the position on the diffraction pattern. The correct set of data is as follows: 31.52° (100), 34.17 (002), 36.01 (101), 47.30 (102), 56.36 (110), 62.68 (103), 66.20 (200), and 67.75 (112). Such set of diffraction angles allows to make the indexation of peaks and to calculate the lattice parameters. If use the DICVOL program, the correct lattice parameters of hexagonal unit cell are: a = 3.2449(4), c = 5.1977(12) Å and γ = 120° for the first sample (heated 3 h). It is necessary to note that the use of DICVOL program (free of charge!) does not require any assumptions on symmetry or hkl and give the results on the basis of all peaks. The formula for lattice spacing d used by Authors requires the above assumptions. At the end, it is necessary to note that it is not good policy to publish the values of crystallite size with decimal This comment refers to the article available online at https ://doi. org/10.1007/s1085 4-016-5823-4.