Crystal structure and electrical properties of textured Ba2Bi4Ti5O18 ceramics

Highly textured Ba2Bi4Ti5O18 ceramic was prepared by spark plasma sintering (SPS). X-ray diffraction of the ceramics revealed the coexistence of a major ferroelectric phase (Space group, SG: B2cb) and a minor paraelectric phase (SG: I4/mmm) at room temperature. A diffused phase transition was observed at around 240 °C. The evolution of the switching current peaks in the electric current vs. electric field (I-E) loops with increasing temperature was interpreted by the structural changes and temperature dependent polarisation reversal processes. The slim polarisation vs. electric field (P-E) loops, the extra switching current peaks in the I-E loops and the non-zero piezoelectric d33 coefficient indicate that Ba2Bi4Ti5O18 is a relaxor ferroelectric material. The recoverable energy density (0.41 ± 0.01 J/cm3) of Ba2Bi4Ti5O18 ceramics in the perpendicular direction to the SPS pressing direction is close to that of Pb(Mg1/3Nb2/3)O3-based ceramics. The obtained results suggest Ba2Bi4Ti5O18 ceramics might be promising for energy storage applications

The features heatmap of C1/C2 illusion images on 8 models.

Feature preferences of eight models under No-Illusion (C1) and With-Illusion (C2) conditions. The stimulus features for C1 are displayed above each model, while those for C2 are shown below.</p

Skye’s Oblique Grating Illusion.

Parallel horizontal bars create a tilted visual illusion effect when black and white diamonds are added in alternating order (A). There are two types of black-and-white diamond positional settings, with each producing opposite tilt effects (B). The tilt strength can be influenced by the width of the diamond.</p

Participant experiments in this study.

Participants provided feedback on visual illusions while observing stimuli on a screen (A). The stimuli were based on RGB color rings with 12 color types (B). There were six diamond width variations (5–10 pixels) and two cases of sequentially alternating diamonds, creating a total of 144 combinations of visual illusion stimuli.</p

The feature heatmap of ResNet101 on Skye’s Oblique Grating Illusion.

We used back-propagation of gradients to compute weights to visualize the feature bias of the DNN on two stimulus images of C1 and C2. The ResNet101 yielded totally four corresponding features on no illusion (C1) and illusion (C2).</p

Comparative evaluation of 8 models in illusion images testing.

The comparative analysis of 8 models on illusion testing using three key performance metrics: Accuracy (deep sky blue bars), Recall (lime green bars), and F1 Score (brown bars), which collectively evaluate the models’ predictive capabilities. Additionally, the chart overlays a line graph (in orange) representing each model’s complexity, measured by the number of parameters (in millions). This dual representation facilitates an understanding of how model complexity correlates with performance across different metrics.</p

Representative dissimilarity matrix (RDM) on different model depths of ResNet101.

We utilized the top-performing illusion response, ResNet-101, in the RDM for testing. Each RDM corresponds to network depth. The horizontal coordinate represents the stimulus images by illusion strengths 1–8, and the vertical coordinate represents the perceived angle images by illusion strengths 1–8. Network depth increased from left to right. The RDM group for Self-data Trained corresponds to the scenario where training is conducted with tilted images, while the RDM group for Pretrained corresponds to the RDM under the condition of pre-training loading (without training).</p

Visual illusion strength on human perceptual adjustment and illusion.

The visual illusion is divided into eight ranges with a threshold of 0.1 degrees, representing eight levels of illusion intensity. On the right are the visual illusion images, corresponding to the human perception adjustment images on the left. Visual illusion images from illusion strength 1 to 4 are categorized under “No-illusion” (C1), while strength 5 to 8 fall under “With-illusion” (C2). There are a total of 144 combinations of visual illusion images, used as the test set. The human perception adjustment images on the left, featuring angled inclinations, serve as the training set for the network, comprising a total of 24,000 images.</p

Comparative analysis of eight models: Performance across varied color and illusion intensities on Skye’s Oblique Grating.

Color Categories (Left Axis): This legend explains the different color bars on the left Y-axis representing various color categories. Each color bar represents the recognition accuracy of the corresponding color in different models. Illusion Intensity Categories (Right Axis): This legend explains the different color bars on the right Y-axis representing levels of illusion intensity. Each color bar represents the recognition accuracy of the corresponding level of illusion intensity in different models.</p

The distribution of 12 colors on C1/C2.

The twelve colors correspond to their respective twelve combinations, distributed in terms of quantity within the “No-illusion” (C1) category with intensities 1 to 4, and the “With-illusion” (C2) category with intensities 5 to 8.</p