Role of Ca additive on the effect of phase composition and microstructure of BaZrO3 refractory and its interaction with titanium alloys

In this study, the effect of different Ca additives (Ca(OH)₂, CaO, and nano-CaCO₃) on the composition and microstructure of the fused BaZrO₃ crucible were investigated, as well as their interaction with Ti₂Ni alloy during vacuum induction melting. Results showed that the crucibles had the same phase compositions when the doping amounts of Ca additives were the same. Three kinds of Ca additives provided three different grain sizes of CaO precursors to participate in the solid solution reaction. When the doping amount of the Ca additive was 5.3 wt.%, the ZrO₂ phase in the fused BaZrO₃ was disappeared, and the CaZrO₃ phase was founded. The composition of the crucibles doped with 7.7 wt.% Ca additives only consisted of Ba_1-xCa_xZrO₃ and CaZrO₃ phase. The relative densities and erosion resistance of the crucibles were improved effectively with the increase of Ca additive content. Moreover, the crucible doped with 7.7 wt.% nano-CaCO₃ additive exhibited the highest density and the thinnest erosion layer. The Ba_1-xCa_xZrO₃ and CaZrO₃ phases were dissolved by the alloy melt, according to the interaction analysis. In addition, the crucible doped with nano-CaCO₃ additive had a higher content of refractory element concentration in the alloy melts in comparision with the other two kinds of crucibles due to their higher number of pores.     

Evaluation of Ca-doped BaZrO3 as the crucible refractory for melting TiAl alloys

In this study, a new Ca-doped BaZrO₃ refractory was designed by using thermodynamics approaches and tested for its applicability for vacuum induction melting (VIM) of TiAl alloys. The influence of CaO on the BaZrO₃ phase constitution and microstructure, as well as the key features of the TiAl melt interaction with the Ca-doped BaZrO₃ crucibles were investigated by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). Results revealed that the Ca-doped BaZrO₃ refractory consisted of Ba_1-xCa_xZrO₃ and CaO phases. An obvious interaction occurred during the melting of the TiAl alloy in the Ca-doped BaZrO₃ crucible along with the generation of BaAl₂O₄ as a reaction product, with formation of a reaction layer up to 5?µm thick. Dissolution of Ca-doped BaZrO₃ refractory in the TiAl melt was the main reason for the alloy-crucible reaction. Moreover, the Ca-doped BaZrO₃ crucible was found to substantially reduce the contamination of the TiAl alloy, with lower oxygen concentration as compared with other conventional oxide crucibles. Overall results confirmed that vacuum induction melting using the Ca-doped BaZrO₃ refractory can be considered as an appropriate method for the fabrication of TiAl alloys.     

Phase and microstructural evolution of BaZrO3-CaZrO3 refractory and its interaction with titanium alloy melt

In this study, the effect of CaZrO₃ additives on the phase and microstructure of BaZrO₃ refractory were investigated as well as the interaction with titanium alloy melts. Results revealed that no second phase was observed in the BaZrO₃ refractory with 10 and 20 mol% CaZrO₃ additives, respectively, and the incorporation CaZrO₃ additives promoted the densification and the growth of grains due to the generation of BaZrO₃-CaZrO₃ solid solutions. Whereas, the appearance of CaZrO₃ phase was in the BaZrO₃ refractory with 30 mol% additive, indicating that the additive content excessed the solid solubility limit in the BaZrO₃ refractory. Interaction analysis indicated that CaZrO₃ additive could improve the performance of BaZrO₃ refractory for resisting the penetration of Ti₂Ni alloy melt. Meanwhile, an increasing extent of melt contamination by the BaZrO₃ refractory was also detected with the increasing content of CaZrO₃ additive. According to the thermodynamic calculation, an obvious increase in Gibbs free energy of formation for the BaZrO₃ refractory was confirmed with the CaZrO₃ additive, resulting in the increasing extent of the dissolution-corrosion between the refractory and the titanium alloy melts.     

On the Modification of Hydration Resistance of CaO with ZrO2 Additive

Various ZrO₂/CaO samples were fabricated by cold isostatic pressing and sintered at 1750°C for 4 h. It was observed that the sample with 12% ZrO₂ additive possessed the good hydration resistance and had the lowest apparent porosity of about 0.75%; its weight additive stored after 56 days was less than 0.6 wt%, and it contributed to the occurrence of CaZrO₃ on the surface of CaO. The CaO crucible with 12 mol% ZrO₂ additive did not react with titanium melt during melting TiNi alloy. This provides a support for searching a new refractory with the good hydration resistance for induction melting titanium alloys.     

Dissolution of BaZrO3 refractory in titanium melt

Although numerous investigations have studied BaZrO₃ as a crucible refractory for melting titanium alloys, the interaction mechanism between them has not been clarified. In this study, a set of three designed alloys with different Ti composition (TiNi, Ti_1.5Ni, and Ti₂Ni) were melted in the BaZrO₃ crucibles. By using the X‐ray diffraction, optical, and scanning electron microscopy analysis, the interactions between the BaZrO₃ crucibles and the titanium melts were investigated. It was found that dissolution of the BaZrO₃ refractory into the titanium melts resulted in the crucible erosion and the melt contamination, the degree of which were both increased with the increasing of Ti content in the melts. The dissolution reaction could be determined as follows: . The oxygen content dissolved in TiNi, Ti_1.5Ni, and Ti₂Ni melts was thermodynamically calculated as 0.0055, 0.1922, and 0.2263 wt%, respectively, which were in agreement with the experimental results.     

Transport properties of proton conductive Y-doped BaHfO3 and Ca or Sr-substituted Y-doped BaZrO3

An electrolyte in fuel cells requires not only high ionic conductivity, but also high transport numbers of ionic conduction. Although Y-doped BaZrO₃ is regarded to be the most promising candidate as the electrolyte in protonic ceramic fuel cells (PCFCs), significant hole conduction generates in wet oxygen at high temperatures. With the aim to increase the transport number of ionic conduction, in this work, Sr and Ca were introduced to partially substitute Ba in BaZr_0.8Y_0.2O_3-δ. The results revealed that a single cubic perovskite phase was obtained for Ba_0.95Ca_0.05Zr_0.8Y_0.2O_3-δ and Ba_1-xSr_xZr_0.8Y_0.2O_3-δ (x = 0.05, 0.10, 0.15, 0.20 or 0.40). However, replacing Ba with Sr resulted in almost no increase in the transport number of ionic conduction in wet oxygen atmosphere, but drastic decrease in proton conductivity at all replacement levels. In addition, Ba_0.95Ca_0.05Zr_0.8Y_0.2O_3-δ shows no meaningful change in the transport number of ionic conduction, compared with BaZr_0.8Y_0.2O_3-δ. Incorporating Ca or Sr into the Ba-site of BaZr_0.8Y_0.2O_3-δ appears to impart no positive influence on electrochemical properties. These interesting results also indicate that the hole conductivity decreases with the decrease in proton conductivity, and will aid to consider the hole conduction mechanism. BaHfO₃ doped with 10 and 20 mol% Y was also prepared. A bimodal microstructure was observed for BaHf_0.9Y_0.1O_3-δ, whereas BaHf_0.8Y_0.2O_3-δ shows uniform grain size after sintering at 1600°C for 24 hours. The transport numbers of ionic conduction and bulk conductivity in such Y-doped BaHfO₃ samples are close to those of BaZrO₃ doped with the same amount of Y.     

Crystal symmetry and magnetism in Ti substituted Bi0.8Ba0.2FeO3 ceramic

The effect of Ti⁴⁺ substitution on the crystal structure and magnetic properties of the Bi_0.8Ba_0.2FeO₃ ceramic nanoparticles was investigated. Bi_0.8Ba_0.2Fe_1−xTi_xO₃ (x=0, 0.05, 0.10, 0.15 and 0.20) ceramics have been prepared by tartaric acid modified sol-gel method. Rietveld refinement of the XRD profile pattern of Bi_0.8Ba_0.2FeO₃ ceramic revealed the formation of pseudo-cubic (Pm3m) phase and confirms structural distortion on incorporation of Ti⁴⁺ ions, which consequently transform pseudo-cubic (Pm3m) structure to tetragonal (P4mm) structure. The saturation magnetization increases appreciably on Ti⁴⁺ ions substitution in Bi_0.8Ba_0.2FeO₃ and is found to be 0.57 emu/g for Bi_0.8Ba_0.2Fe_0.95Ti_0.05O₃ ceramic. The increase in the magnetization by the substitution of non-magnetic Ti⁴⁺ ions has been ascribed to crystal structure modification made by the Ti⁴⁺ ions. However, a sudden decrease in the magnetization has been observed for Bi_0.8Ba_0.2Fe_0.8Ti_0.2O₃ ceramic nanoparticles. The prominent Ti (3d) – O (2p) hybridization would stabilize the ferroelectric distortion and consequently reduce the magnetization. Scanning Electron Microscope (SEM) image of Bi_0.8Ba_0.2Fe_0.8Ti_0.2O₃ ceramic sample revealed the formation of dense microstructure with uniform grains size.     

Manipulation of ZrO2/CaZrO3 fibrous membrane with high thermal stability and NIR reflectivity

Grain size control is an important aspect to manipulate the microstructure and high temperature stability of ceramic fibers. In the present work, phase competition mechanism was proposed to regulate the grain size of ZrO₂/CaZrO₃ composite fibers. Calcium precursor with different molar ratio of Ca/Zr was introduced to the zirconia system not only for phase stabilization of ZrO₂ but also for phase competition between solid-solution Ca_xZr_1-xO_2-x and new phase CaZrO₃. Effects of Ca/Zr molar ratio on the thermal pyrolysis, crystallization, solid reaction of precursor fibers were fully explored. The change of grain size of fibers with various Ca/Zr molar ratio was characterized and discussed. Furthermore, the near-infrared reflectivity and high-temperature stability of fibrous membranes were also presented. The results indicated that ZrO₂/CaZrO₃ fibrous membrane has promising applications in high-temperature for the excellent thermal stability and high near infrared (NIR) reflectivity.     

Wetting and spreading of Ca-Y-Ba-Cu-O solution on Y2O3 and CaSZ crucible in growing Y1-xCaxBa2Cu3O7-δ single crystal

Sizable and uniform Y_1-xCa_xBa₂Cu₃O_7-δ single crystals are of significant importance to study high-temperature superconductivity. However, the severe liquid loss resulting from intrinsic wetting property during top-seeded solution-growth (TSSG), makes it difficult to obtain such crystals. Here the reactive wetting performance of the Ca-Y-Ba-Cu-O solution on two types of crucibles was studied. It was identified that the spreading process on the Y₂O₃ crucible is characterized by forming double-layer of Y₂BaCuO₅ and YBa₂Cu₃O_7-δ, while that on the CaSZ crucible (Ca-stabilized ZrO₂) produces the BaZrO₃ layer with CuO phase. In the former case, the liquid has a low energy interface with the top layer of YBa₂Cu₃O_7-δ, leading to strong spreading and creeping behaviors. Conversely, due to a high interfacial energy between solution and BaZrO₃, the CaSZ crucible has a low wettability, particularly beneficial to solve the liquid loss problem. Consequently, with negligible liquid creeping out of CaSZ crucibles, we succeeded in growing a series of homogeneous Y_1-xCa_xBa₂Cu₃O_7-δ single crystals with an acceptable size up to a × b × c = 11.2 × 11 × 4.8 mm³. Moreover the wetting modes of solution on various kinds of crucibles for TSSG in growing doped YBa₂Cu₃O_7-δ single crystals were also elucidated. Most importantly, the understanding gained from this work is broadly applicable for producing other desirable doped-crystals.     

High-temperature mechanical and thermal properties of Ca1−xSrxZrO3 solid solutions

Perovskite oxides are promising thermal barrier coatings (TBCs) materials but their thermophysical properties still need to be further improved before commercial applications. In this work, mechanical/thermal properties of calcium-strontium zirconate solid solutions (Ca_1−xSr_xZrO₃) are investigated. Comparing to the end-compounds CaZrO₃ and SrZrO₃, the solid solutions achieve the enhanced thermal expansion coefficient, decreased thermal conductivity as well as good high-temperature mechanical properties. The experimental thermal conductivities of Ca_1−xSr_xZrO₃ (x = 0.2, 0.4, 0.6, 0.8) are in the range of 1.76-1.94 W·(m·K)⁻¹ at 1073 K, being lower than that of the yttria-stabilized zirconia (YSZ). At the same time, their thermal expansion coefficients (10.75 × 10⁻⁶-11.23 × 10⁻⁶/K at 1473 K) are comparable to that of YSZ. Moreover, the Young's moduli of Ca_0.8Sr_0.2ZrO₃, Ca_0.6Sr_0.4ZrO₃, Ca_0.4Sr_0.6ZrO₃, and Ca_0.2Sr_0.8ZrO₃ at 1473 K are 70.7%, 69.4%, 68.8%, and 71.1% of the corresponding values at room temperature, respectively. The good high-temperature mechanical and thermal properties ensure the potential applications of Ca_1−xSr_xZrO₃ solid solutions as high-temperature thermal insulation materials including TBCs.     

Sintering behavior of Y-doped BaZrO3 refractory with TiO2 additive and effects of its dissolution on titanium melts

In this study, the sintering behavior of Y-doped BaZrO₃ with TiO₂ additive and effects of its dissolution on titanium melts were investigated. In order to overcome the difficulty of Y-doped BaZrO₃ sintering performance, the 0-5 wt% TiO₂ was added into Y-doped BaZrO₃ and its densification was investigated by density analyzer, scanning electron microscope (SEM) and X-ray diffraction (XRD). Thereafter, the interface reaction between two crucibles (without and with 2 wt% TiO₂) and titanium alloys, the thermodynamics and kinetics of dissolution reaction were also investigated. The results showed that Y-doped BaZrO₃ was rarely dense without TiO₂ additive and its relative density was just 88%, while after doping 2 wt% TiO₂, the relative density was more than 97%. However, with the excessive TiO₂(>2 wt%) doping, the secondary phase was observed by SEM and XRD. After melting titanium-rich alloys (Ti₂Ni, 66 mol% Ti) by Y-doped BaZrO₃ crucibles without and with 2% TiO₂ additive, the erosion layer of the two crucibles was approximately 4000 and 1700 μm, respectively. It was also found that the dissolved reaction rate was related to the density and grain size of Y-doped BaZrO₃ ceramic; the higher density and larger grain size ceramics can effectively prevent the crucible from being eroded by Ti₂Ni melt.     

Performance of BaZrO3/Y2O3 dual-phase refractory applied to TiAl alloy melting

Vacuum induction melting is a potential process for the preparation of TiAl alloys with good homogeneity and low cost. But the crucial problem is a selection of high stability refractory. In this study, a BaZrO₃/Y₂O₃ dual-phase refractory was prepared and its performance for melting TiAl alloys was studied and compared with that of a Y₂O₃ refractory. The results showed the dual-phase refractory consisted of BaZr_1-xY_xO_3-δ and Y₂O₃(ZrO₂), exhibited a thinner interaction layer (30 μm) than the Y₂O₃ refractory (90 μm) after melting the TiAl alloy. Although the TiAl alloys melted in the dual-phase and Y₂O₃ refractory exhibited similar oxygen contamination (<0.1 wt%), the alloy melted in the dual-phase refractory had smaller Y₂O₃ inclusion content and size than that in the Y₂O₃ refractory, indicating that the dual-phase refractory exhibited a better melting performance than the Y₂O₃ refractory. This study provides insights into the process of designing highly stable refractory for melting TiAl alloys.     

Microstructural evolution and interfacial reactions between Ti and ZrO2/CaTiO3 composites

Various proportions of ZrO₂/CaTiO₃ powders were mixed and hot pressed at 1500°C/30 min for Ti casting. The hot-pressed ZrO₂/CaTiO₃ composites were reacted with pure Ti at 1700°C/10 min in Ar. The interfacial reaction between Ti and ZrO₂/CaTiO₃ composites was investigated through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The ZrO₂/CaTiO₃ composites with less than 10 vol.%, CaTiO₃, and a minor amount of residual TiO₂ were found. When the content of ZrO₂ was increased to larger than 10 vol.%, two Ca₂Zr₅Ti₂O₁₆ and CaZrTi₂O₇ phases appeared in the composites. The amount of CaTiO₃ and CaZrTi₂O₇ in the composites gradually decreased as the amount of ZrO₂ increased. When Ti came in contact with ZrO₂/CaTiO₃ composites with less than 10 vol.% ZrO₂, the resulting eutectic reaction produced a liquid phase and induced melting. When ZrO₂ was increased to more than 30 vol.% in the composites, Ca₂Zr₅Ti₂O₁₆ and CaZrTi₂O₇ changed completely to CaZrO₃, Ti₂O, CaO, and ZrO₂. With more than 30 vol.% ZrO₂, no other reaction phases occurred in the Ti side after contact with the ZrO₂/CaTiO₃ composites, which is conducive for producing ceramic composites for Ti casting applications.     

Enhanced thermal stability of piezoelectricity in lead-free (Ba,Ca)(Ti,Zr)O3 systems through tailoring phase transition behavior

Good thermal stability in lead-free BaTiO₃ ceramics is important for their applications above room temperature. In this study, thermal stable piezoelectricity in lead-free (Ba,Ca)(Ti,Zr)O₃ ceramics was enhanced by tailoring their phase transition behaviors. Comparison between (1-x)Ba(Ti_0.8Zr_0.2)O₃-x(Ba_0.65Ca_0.35)TiO₃ and (1-y)Ba(Ti_0.8Zr_0.2)O₃-y(Ba_0.95Ca_0.05)TiO₃ revealed that latter system at y?=?0.80 had much better thermal stable piezoelectric coefficient than the former at x?=?0.45. Both systems crystalized in tetragonal to orthorhombic phase boundary at room temperature. The phase transition temperature and degree of diffusion were adjusted by Ca and Zr ions contents and demonstrated great influence on temperature dependent dielectric permittivity, hysteresis loops, and in-situ domain structures. The improved thermal stability of (1-y)Ba(Ti_0.8Zr_0.2)O₃-y(Ba_0.95Ca_0.05)TiO₃ prepared at y?=?0.80 was linked to its higher paraelectric to ferroelectric phase transition temperature (T_m?=?115.7?°C) and less degree of diffusion (degree of diffusion constant γ?=?1.35). By comparison, (1-x)Ba(Ti_0.8Zr_0.2)O₃-x(Ba_0.65Ca_0.35)TiO₃ prepared at x?=?0.45 revealed T_m?=?81.3?°C and γ?=?1.65. Overall, these findings look promising for future stimulation of phase transition behaviors and design of piezoelectric materials with good thermal stabilities.     

BaZrO3 refractory crucibles for vacuum induction melting of industrial Zr-based bulk metallic glass master alloys with Y addition

The absence of appropriate melting method and expensive cost of high-purity Zr raw material limit the commercial application of Zr-based bulk metallic glass. In the present study, using high oxygen industrial grade sponge Zr as raw material and the metal Y as additive, the low-cost and high-purity master alloys were successively prepared using a VIM method with a BaZrO₃ refractory crucible. The results indicate that the BaZrO₃ refractory exhibited good erosion resistance to the alloy melt, the Y additive formed the Y₂O₃ barrier layer on the surface of crucible, which prevented the melt permeation into the crucible, then effectively reduced the thickness of the erosion layer. In addition, the metal Y deoxidizer could remove the oxygen of melts, finally the low oxygen Zr-based master alloy (about 0.02 wt%) was prepared. These results may provide a promising preparing technique prototype of low-cost Zr-based bulk metallic glass.     

Failure mechanism of the Y2O3 doped BaZrO3/Al2O3 composite ceramic mould during directional solidification of TiAl-Based alloys

Directional solidification of Ti–46Al–8Nb (at.%) intermetallic in the Y₂O₃ doped BaZrO₃/Al₂O₃ composite ceramic mould was carried out using Bridgman apparatus. To increase the success rate of Ti–46Al–8Nb single crystals preparation and improve the quality of the ingots, the failure mechanism of the mould in directional solidification experiments was evaluated. Nucleation and propagation of cracks in the moulds were investigated by tracing each key process of the experiment, the effect of pores in the mould on the target alloy was revealed by studying the mould/metal interface. The results show that the macrocracks in the facecoat of the mould would lead to the leakage of the alloy melt. Furthermore, the alloy melt would infiltrate into the mould through large-size pores, which would increase the oxygen content of the target alloy, and also form inclusions containing O, Zr, Si and Y elements in the alloy ingot.     

Corrosion resistance of calcium zirconate crucible to titanium-copper melts

The corrosion resistance of refractory materials to the titanium alloy melts is vital for the production of titanium alloys by vacuum induction melting. In this study, the corrosion behavior of calcia-stabilized zirconia, solid state synthesized calcium zirconate, and fused calcium zirconate refractory suffering Ti-5 wt% Cu melts were investigated at 1680 ℃ for 15 min of soaking time by the cup test method. It was found that the three crucibles directly dissolved into the titanium melt, then generated Ti (Zr, O) and CaZrO₃ in the infiltration layer, and eventually developed a porous Ti₃O layer in the lining. Besides, the contamination of Ti-5 wt% Cu alloy (oxygen: 5.3 wt%; zirconium: 6.01 wt%; calcium: 0.42 wt%) by fused calcium zirconate crucible was significantly less than the solid state synthesized one (oxygen: 5.83 wt%; zirconium: 6.14 wt%; calcium: 0.43 wt%), implying that the production method of calcium zirconate notably affected the impurity of titanium alloys.     

Structure,mechanical properties,and thermal conductivity of BaZrO3 doped at the A-B site

BaZrO₃ with the ABO₃ perovskite structure can be doped at the A or B sites to obtain the corresponding properties. In this study, BaZrO₃ was doped with Ca²⁺, Sr²⁺, Ti⁴⁺, and Ce⁴⁺. The structure, phase composition, and mechanical and thermal properties of the composites were investigated. The sintered Ba_1-xCa_xZrO₃ samples with x = 0.2 and 0.4 exhibited relatively superior comprehensive behaviours; the cold modulus of rupture was increased by 127.36% and 134.59%, while that for BaZr_0·8Ti_0·2O₃ and BaZr_0·8Ce_0·2O₃ was increased by 99.30% and 112.37%, respectively. Further increases in strength and density were obtained in the Ba_0·8Ca_0·2Zr_0·8Ti_0·2O₃ and Ba_0·6Ca_0·4Zr_0·8Ti_0·2O₃ co-doped samples, and the corresponding apparent porosities were greatly decreased from 30.6% to below 1.0%. The thermal conductivities of the doped samples were generally low, achieving a minimum of 0.361 W/(m·K). The combination of high strength and low thermal conductivity demonstrate the significant application potential of BaZrO₃-based composite materials.     

Microwave absorption of M-type hexaferrite Ba1-xCaxFe12O19 (x ≤ 0.4) ceramics in 2.6–18 GHz

Ba_1-xCa_xFe₁₂O₁₉ (x?=?0.0, 0.1, 0.2, 0.3 and 0.4, BCFO) ceramics were prepared using high-temperature solid-state method and the effect of Ca²⁺ substitution was investigated. The grain size of BCFO ceramics sintered at 1250?°C for 2?h increases from 1?µm to 5?µm as Ca²⁺ added. The BCFO ceramics show a typical hard magnetic behavior with a maximum saturation magnetization (M_S) of 51.8?emu?g^?1 at x?=?0.2. The bandwidth of microwave reflection loss (RL) below ??10?dB (> 90.0% microwave absorption) is obtained in 7.60???9.8?GHz with the minimum RL ??30.8?dB at 8.5?GHz for x?=?0.2 (thickness 2.0?mm), which makes Ba_0.8Ca_0.2Fe₁₂O₁₉ ceramic a potential microwave absorption candidate.     

Evolving antiferroelectric stability and phase transition behavior in NaNbO3-BaZrO3-CaZrO3 lead-free ceramics

The stability of antiferroelectricity in NaNbO₃ ceramics was found to evolve with co-doping x mol% CaZrO₃ and 6 mol% BaZrO₃, from a dominant ferroelectric (FE) orthorhombic Q phase (x = 0) to a gradually stabilized antiferroelectric (AFE) orthorhombic P phase owing to different ionic radii of Ba and Ca ions. Although a complete AFE P phase appears at x = 0.5, the field induced AFE-FE phase transformation is irreversible at first, and then becomes partially reversible at x = 1 and finally completely reversible at x = 3. The above-mentioned change process proves to be associated with the enhancing stability of antiferroelectricity with x, as evidenced by means of dielectric, polarization and strain properties as well as in/ex-situ synchrotron x-ray diffraction and Raman spectra. A composition-field phase diagram for the NN-based lead-free AFE ceramic was constructed on basis of the phase structural change, which would provide a clear understanding of how ion doping influences its antiferroelectricity.