Microstructure and microwave dielectric properties of nonstoichiometric 1:1 ordered Nd(Zn1/2Ti1/2+x)O3+2x perovskite ceramics with Ti4+ self-doping

The grain size, B-site 1:1 cation ordering, chemical defects and microwave dielectric properties of the non-stoichiometric Nd(Zn1/2Ti1/2+x)O3+2x (x = -0.02-0.02) complex perovskite ceramics were significantly tuned by self-doping methods. The increase of Ti4+ self-doping significantly increases the grain size of Nd(Zn1/2Ti1/2+x)O3+2x ceramics which could still maintain a monoclinic structure with B-site 1:1 cation ordering (space group P2(1)/n) in the case of deviation from stoichiometry. However, the degree of 1:1 B-site cation ordering is tuned to be negatively correlated with the mutual occupancy of Ti4+ and Zn2+ by Ti4+ self-doping according to the results of crystal structure refinement. With the increase of Ti4+ component, the degree of 1:1 cation ordering first increased and then decreased, reaching the maximum value (S = 0.81) at x = 0.01. Non-stoichiometry can tune cation ordering because it modulates the effective radius difference and charge difference of B-site ions. The increase Ti4+ component promotes the formation of ordered domains with uniformly distributed domain boundaries and increasing domain size up to x = 0.01. With further increase of Ti4+ component to x = 0.02, ferroelastic domains appear due to the oxygen octahedral torsion. The B-site 1:1 cation ordering significantly reduces the dielectric loss of the ceramics, which makes the Q x f value exhibit the same variation rule as the degree of B-site 1:1 cation ordering. High Q x f value of 58000 GHz is achieved in the non-stoichiometric samples (x = 0.01), and it is 45% higher than those in traditional stoichiometric samples (x = 0). In this work, the microstructure and properties of the ceramics are effectively regulated by non-stoichiometry, which provides an effective way to tune the properties of 1:1 ordered ceramics.