The photocatalytic activity of the samples was

X-ray diffraction (XRD) profiles were obtained at room temperature in a Bruker D8 diffractometer with a Sol-X MK-2461 dispersive detector, using Cu Kα filtered radiation (λ = 0.15418 nm) in the 2θ range 2–70° with a scanning rate of 1.5° min−1. The structural identification was performed by using the JCPDS cards [30]. Average crystal size (D) was calculated from the most intense diffraction peak (1 0 1) using the Scherrer’s equation [31]. Variable temperature XRD (VT–XRD) profiles were performed using an X’Pert Pro Panalytical diffractometer with Ni filtered Cu-Kα radiation and a xenon detector. To perform the high temperature experiments, an anton paar HTK120 heating stage was used, integrated with the Panalytical control software. The as-prepared powders were loaded onto an alumina heater stage. This heater enclosure was purged with air at a flow rate of 2 mL min−1. The sample was further heated at a rate of 10 °C min−1 up to a maximum of 800 °C. The sample was held at several target temperatures (each 100 °C) for up to 130 min. During skeletal system hold time, the sample temperature was maintained constant and XRD data were collected over the 2θ range 3–70° with a step size of 0.04° and a count time of 4 s.