Figure 1 shows the evolution of (00

Figure 1 shows the evolution of (002)/(110) peak intensity ratio of ZnO phase for the various contents of polymer. As a global trend, this ratio is increasing with polymer content,pointing out an anisotropic orientation of grains. This may originate from two different phenomena: (i) grain growth can occur during sintering, with a preferential crystallographic orientation or (ii) there may be a grain rotation during the sintering process, leading to crystal alignment. In the CSP, an important pressure is applied on the sample, so it is difficult for particles to rotate and orientate along a particular crystallographic axis. However, this anisotropy suggests a preferential crystal growth induced by the sintering process, which is apparently promoted by the presence of PTFE. ZnO is known to have preferential growth along [00l] direction, as it has already been observed in the case ZnO sintering using water as a transient liquid phase, and even enhanced in the presence of acetic acid [16]. Thus, it is not surprising to observe crystal growth along (00l) direction, but the influence of PTFE is not obvious.