Six X-ray photographs were taken at different temperatures between 30 and 105 ° C, using a back-reflection focusing camera mounted on an X-ray generator fitted with copper target. The reflections, which were unambiguously indexed and used in the evaluation of the lattice parameters, were (50 l l)~ja2, (547)aL~2, (0016)71a2, (705)~1~ 2, (637)~1~z, and (716)7~c~2, recorded in the Bragg angle region
... [Show full abstract] between 66 ° and 84 ° . The values of the lattice parameters at different temperatures are given in Table I. The standard errors in the values of the lattice parameters, a and c, at room temperature were found to be 4- 0.000 02 nm and 4- 0.000 03 nm, respectively. The errors at higher temperatures were found to be of the same order. Using a semi-analytical approach suggested by Deshpande and Mudholkar [6] the values of the principal coefficients of thermal expansion (~a along the a-axis and ~,. along the c-axis) were evaluated at dif